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22nd National Conference on Atomic and Molecular Physics
ABSTRACT BOOK
25th
March 2019 – 28th
March 2019
Organized by Dept. of Physics, Indian Institute of Technology Kanpur
in association with
Indian Society of Atomic and Molecular Physics and
Science and Engineering Research Board (SERB), Govt. of India
National Advisory Committee E. Krishnakumar (RRI, Bengaluru) Rajesh Srivastava (IIT Roorkee) P. C. Deshmukh (IIT Tirupati) Lokesh C. Tribedi (TIFR, Mumbai) Minaxi Vinod Kumar (V.P. & R.P.T.P. Science College, VallabhVidya Nagar) B. N. Rajasekhar (BARC, Mumbai) R. Shanker (BHU, Varanasi) Amit Roy (VECC, Kolkata) G. Ravindra Kumar (TIFR, Mumbai) SudeepBhattacharjee (IIT Kanpur)
Local Organizing Committee Aditya H. Kelkar(Convenor) IIT, Kanpur C. P. Safvan(Co-Convenor) IUAC, Delhi R. Vijaya (HOD), IIT Kanpur M. K. Harbola, IIT Kanpur H. Wanare, IIT Kanpur V. Subrahmanyam,IIT Kanpur Anjan K. Gupta, IIT Kanpur AnandJha, IIT Kanpur Saikat Ghosh, IIT Kanpur
Index
1) Highly charged Ion collisions with large molecules: Recent Trends
Lokesh C. Tribedi
PT-1
2) Manipulating Light Quanta Urbasi Sinha
PT-2
3) Reliable plasma modeling through electron impact excitation of inert gases Rajesh Srivatstava
PT-3
4) Ion beams from plasmas driven by electromagnetic waves: physics and applications Sudeep Bhattahcarjee
PT-4
5) Radiolysis of Nucleobases at Low Temperatures: Radio-Resistance Measurements Aditya N. Agnihotri
IT-1
6) Kinetic energy release in dissociation of NH3q+ under ion impact Pragya Bhatt
IT-2
7) Photo-absorption studies on gas phase biological chromophores Jyoti Rajput
IT-3
8) Studying ion dynamics with Electrostatic Ion Beam Trap Koushik Saha
IT-4
9) The Cryogenic Storage Ring CSR Preeti Mishra
IT-5
10) A global search for an unlimited, sustainable energy source for future generations R. Shanker
IT-6
11) Study of atom localization in different atomic system via spatial dependent probe absorption Ajay Wasan
IT-7
12) Polarization Rotation in a Coherent Atomic Medium Sankar De
IT-8
13) Density functional theory based study of a two-dimensional gas of dipolar fermions in a harmonic trap Aroop Banerjee
IT-9
14) Multielectron processes in van der Waals aggregates hosted in private quantum fluid cryostats unraveled by coincidence spectroscopy Sivarama Krishnan
IT-10
15) Ionization asymmetries and molecular orientation in two-color laser strong fields N. Bhargava Ram
IT-11
16) Wakefield generation and the formation of EM soliton in relativistic plasmas A. P. Misra
IT-12
17) Low energy free electron induced chemistry Vaibhav S Prabhudesai
IT-13
18) Electron driven DEA study with targets of applied interest Minaxi Vinodkumar
IT-14
19) Turbulance in space plasmas Supratik Banerjee
IT-15
20) Multiwavelength imaging and numerical simulation of solar coronal transients Ramit Bhattacharyya
IT-16
21) Dynamics and control of photon transport in coupled cavities Nilkantha Meher
OP-1
22) Photoabsorption studies of nitromethane using synchrotron radiation Aparna Shastri
OP-2
23) Post ionization alignment effect in O2+ Arnab Sen
OP-3
24) Study of multiply charged Argon recoil ions formed under 3.5 keV electron impact using electron-ion coincidence technique Sunil Kumar
OP-4
25) An extensive study of Pyrrole biomolecule through electron scattering Hardik Desai
OP-5
26) Particle balance in a plasma confined in a dipole magnetic field Anuj Ram Baitha
OP-6
27) Ion induced dissosciation of methane Diksha Garg , C.P. Safvan, Jyoti Rajput
P-01
28) Design And Implementation of Post Collision Charge State Analyser Jatin Yadav, Herendra Kumar, Diksha Garg, Pragya Bhatt, C.P. Safvan and Jyoti Rajput
P-02
29) Theoretical predictions for ionization cross sections of bio-molecules by high energy proton impact S. Sammadar, M. Mondal, A. Mondal, K. Purkait and M. Purkait
P-03
30) Electrostatic post-collision analyzer to study charge exchange processes Sumit Srivastav, Deepak Sharma and Bhas Bapat
P-04
31) Model Calculation To Study The Orientation Effect In Multiple Ionisation Of Diatomic Molecule Deepak Sharma , Bhas Bapat , Pragya Bhatt and C P Safvan
P-05
32) Kinetic energy release in dissociation of NH3q+ under ion impact Pragya Bhatt, T. Sairam and C. P. Safvan
P-06
33) Delayed dissociation of ethylene under ion impact Pragya Bhatt, K. Takahashi, K. Yokokawa, A. Mizumura, J. Matsumoto, H. Kumar, C. P. Safvan, and H. Shiromaru
P-07
34) Electron Beam Ion Source (EBIS) Facility at IISER, Pune Deepak Sharma, Sumit Srivastav, Suddhasattwa Mandal, Arnab Sen and Bhas Bapat
P-08
35) Tuning Optical Properties of Metallic Thin Film Mirrors by Low Energy Inert Gaseous Ion Beams Krishn Pal Singh, Jayashree Majumdar and Sudeeep Bhattacharjee
P-09
36) Development of Time-Dependent Schrodinger Equation solver and Its application to calculate High-order Harmonic Generation by laser-atom interaction Rambabu Rajpoot, Amol R. Holkundkar and Jayendra N. Bandyopadhyay
P-10
37) Photoelectron velocity map imaging spectroscopy facility for probing anion resonances Saroj Barik and G. Aravind
P-11
38) Spin-orbit interaction effect in Wigner-Eisenbud-Smith time delay: a case study on Xe 3d photoionization Sourav Banerjee, Ankur Mandal, Soumyajit Saha, and Pranawa C. Deshmukh
P-12
39) 3rd oder nonlinearity based on wavelength mismatching and quantum interference in microwave driven Y-type atomic system Neeraj Singh and Ajay Wasan
P-13
40) Multi Window Ladder Type Electromagnetically Induced Transparency in 87Rb Atomic Medium at Room Temperature Vikas S.Chauhan, Sumit Bhushan and Raghavan K. Easwaran
P-14
41) R-matrix calculations of the photoionization cross sections of Co17+ Mayank Dimri, A. K. Singh and Man Mohan
P-15
42) Photoionization of the ground 3s2 (1S0) and excited 3s3p (3Po0,1,2) states of Se XXIII and atomic data of Se XXIV Dishu Dawra, A. K. Singh and Man Mohan
P-16
43) Simultaneous control of harmonic yield and energy cutoff of high-order harmonic generation using seeded plasmonically enhanced fields Irfana N. Ansari, M. S. Mrudul, Marcelo F. Ciappina, Maciej Lewenstein and Gopal Dixit
P-17
44) Real-Space Recollision Picture in High-Harmonic Generation from Solids Mrudul M. S., Adhip Pattanayak, Misha Ivanov and Gopal Dixit
P-18
45) Effects of Vacancy In Solid High Harmonic Generation Adhip Pattanayak, Mrudul M.S and Gopal Dixit
P-19
46) Ion Trapping results of High Intensity Laser Ion Trap Experiment (HILITE) at GSI, Germany Sugam Kumar, S. Ringleb, N. Stallkamp, M. Vogel, W. Quint, Th. Stohlker and C.P. Safvan
P-20
47) Role of Helium Nanodroplet Environment on the Ionization Dynamics of Acetylene Under EUV Synchrotron Radiation Suddhasattwa Mandal, Ram Gopal, Robert Richter, Marcello Coreno, Marcel Mudrich, Alessandro D’Elia, Mykola Shcherbinin, Hemkumar Srinivas, Bhas
P-22
Bapat, Sivarama Krishnan and Vandana Sharma
48) Supercontinuum generation in Argon through hollow core fiber for use in atomic and molecular physics experiments Pritha Dey, C. Vijayan and Sivarama Krishnan
P-23
49) Doppler-free spectroscopy of thermal Rubidium atoms for laser frequency stabilization Rajni Bala, Omshankar, Ingo Nosske, Vivek Venkataraman and Joyee Ghosh
P-24
50) Electron impact cross section study of Furfural A.Chaudhari, H.Bhutadia, C. Limbachiya and M. Vinodkumar
P-25
51) Cross sectional study of pyridazine molecule on electron impact H. Bhutadia, A. Chaudhari, M. Vinodkumar and C. Limbachiya
P-26
52) Low energy electron interactions with Iodine molecule (I2) Hitesh Yadav, Minaxi Vinodkumar and P. C. Vinodkumar
P-27
53) Electron capture cross sections from biological molecules by bare projectile impact A. Mondal, K. Purkait, S. Samaddar, S. Halder and M. Purkait
P-28
54) Probing Functional Group Dependence in Dissociative Electron Attachment to Pyrrole Using Negative Ion Momentum Imaging Samata Gokhale, Krishnendu Gope, Vishvesh Tadsare, Matthew Bain and Michael N R Ashfold, E. Krishnakumar and Vaibhav S. Prabhudesai
P-29
55) Absolute double differential cross section of bremsstrahlung radiation produced in collisions of 3.5 keV electrons with free SF6 molecule. S. Prajapati, B. Singh, B.K. Singh and R. Shanker
P-30
56) Electron impact excitation of highly charged Ge-like xenon ion Swati Bharti, Lalita Sharma and Rajesh Srivastava
P-31
57) H- Production from H2 by dissociative electron attachment and dipolar dissociation in the energy range 0.5eV to 100eV Suvasis Swain, E. Krishnakumar and Vaibhav S. Prabhudesai
P-33
58) Study of Electron Excitation and polarization of Tungsten Ions Neelam Shukla, Priti, Lalita Sharma, and Rajesh Srivastava
P-34
59) Electron impact fine structure excitation of xenon and Plasma Modeling Priti, R K Gangwar and R Srivastava
P-35
60) Electron impact elastic scattering cross sections of H2S D. Mahato, L. Sharma and R. Srivastava
P-37
61) ELECTRON IMPACT EXCITATION OF HIGHLY CHARGED Ge LIKE Ba IONS P. Malker, and L. Sharma
P-38
62) Calculations for partial ionization cross sections for n-ethanol molecule by electron collision R. Singh, Manoj Kumar and S. pal
P-39
63) Dissociative Electron Attachment to Jet Cooled Oxygen Molecules Irina Jana, Varun Ramaprasad and Dhananjay Nandi
P-40
64) Electron induced scattering from butane Dineshkumar Prajapati, Hitesh Yadav, Minaxi Vinodkumar and P. C. Vinodkumar
P-41
65) Theoretical Studies Of Electron Impact on Formyl Fluoride Tejas Jani, Hitesh Yadav, Dineshkumar Prajapati, Minaxi Vinodkumar and P. C. Vinodkumar
P-42
66) Electron assisted elastic and inelastic processes for perfluoroketone (PFK) molecules Mohit Swadia, Nirav Thakkar, Minaxi Vinodukmar and Chetan Limbachiya
P-43
67) Emission and detection of energy selected electrons produced in low energy electron interaction with free Argon atom. Manish Kumar Singh, S.Prajapati, B.Singh, S.Kumar, S.K.Singh, B.K.Singh, R.Shanker
P-44
68) Triple Differential Cross Section for the electron impact ionization of atoms and molecules Nikita Dhankhar, Aditi Mandal and Rakesh Choubisa
P-45
69) Electron scattering total cross section of Butatrienylidene (H2CCCC): A cumulene carbene detected in interstellar medium. Nafees Uddin, Pankaj Verma and Bobby Antony
P-46
70) Low temperature neon plasma Diagnostics with fully relativistic electron impact excitation cross-sections S. S. Baghel, S. Gupta, R. K. Gangwar and R. Srivastava
P-47
71) Measurement of angular distribution of Lα,β,γ x-ray intensity of Pt thick target following impact of 10-25 keV electrons B. Singh, S.Prajapati, B.K. Singh and R. Shanker
P-48
72) Effect of strong magnetic field on optical emissions from atmospheric pressure micro-plasmas Kalyani Barman, Deepika, Mohit Mudgal, Sudeep Bhattacharjee, Ramkrishna Rane and S.K. Nema
P-49
73) Study of Electron interactions with Plasma Processing gases Rakesh Bhavsar, Yogesh Thakar, Dhaval Chauhan and Chetan Limbachiya
P-50
74) Collisional radiative model for Ar/N2 mixture plasma with fine structure resolved electron impact excitation cross sections Shivam Gupta , R.K. Gangwar and Rajesh Srivastava
P-52
75) Spectroscopic Studies of Cold Atomic Hydrogen in Aditya-U Tokamak Edge Nandini Yadava, J. Ghosh, Sripathi Punchithaya K, M. B. Chowdhuri, R. Manchanda, S. Banerjee, Ritu Dey and Aditya-U team
P-53
76) Structural behaviour of diamagnetic cavity in laser-produced plasma Narayan Behera, R. K. Singh and Ajai Kumar
P-54
77) Electronic state spectroscopy of methacrolien. Sunanda K, A. K. Das and B.N. Rajasekhar
P-55
78) Spectroscopic studies on Crotonaldehyde in the VUV region A. K. Das, S. Krishnakumar and B.N. Rajasekhar
P-56
79) Vibrational Spectroscopic studies on 2,3-Dihydrobenzofuran-5-carboxaldehyde D.Vijay, Asim Kumar Das, B N Rajasekhar and A.Veeraiah
P-57
80) Studies on electronic and vibrational spectroscopic properties of propanol structural isomers Param jeet Singh, Sunanda K., Asim Kumar Das, A.P.Mishra and B.N. Rajasekhar
P-58
81) Nanoparticle enhanced LIBS of Cu target using pulsed Nd: YAG laser as excitation source Swetapuspa Soumyashree, Nageswara Rao E., Prashant Kumar, Pooja Chandravanshi, Madhusudhan P, Rajesh K. Kushawaha, S.B. Banerjee, K.P. Subramanian
P-59
82) Estimation of elemental concentration using plasma emission spectroscopy employing synthetic spectrum method E. Nageswara Rao, Prashant Kumar, Swetapuspa Soumyashree, Pooja Chandravanshi, Rajesh K Kushawaha, Swaroop Banerjee and K P Subramanian
P-60
83) IR attenuation due to phase changes from amorphous to crystalline in astrochemical propargyl ether ices K. Rahul, J Meka, A Das, B N Raja Sekhar, B – M Cheng, N J Mason, B Sivaraman
P-61
84) Reversible phase change observed in 1-hexyne astrochemical ices J Meka, K Rahul and B Sivaraman
P-62
85) The AstroChemical Ices Database (ACID) and its access through SSHADE V. Bhushit, K. Rahul, M. Dinesh, L. Chetan, B –M Cheng, N J Mason and B Sivaraman
P-63
86) Theoretical investigations on electronic structure of 4,4′ dibromobiphenyl, a flame-retardant material Kiran Kumar Gorai, Aparna Shastri, Asim Kumar Das and S. N. Jha
P-64
87) Interaction potentials and collision cross sections for ultracold 7Li+-7Li ion-atom system A. Pandey, M. Niranjan, N. Joshi, S. A. Rangwala, O. Dulieu
P-65
88) Resonance Revival in Elastic Scattering of H Atom with Variants of C60 Km Akanksha Dubey, ShwetaAgrawal, T. Rajagopala Rao and Jobin Jose
P-66
89) Analysis of 5s2 5p4 - 5s2 5p3 5d transitions in seventh spectrum of cerium Abdul Wajid and S.jabeen
P-67
90) Establishment of ground configuration and MCDHF calculations for seven times ionized Cerium: Ce VIII Abdul Wajid and S.jabeen
P-68
91) The Rydberg and dissociative states of CH:An R-Matrix study K.Chakrabarti, R.Ghosh and B.S.Choudhury
P-69
92) The 5p65d7-5d65f transition array in the fifth spectrum of gold: Au V Aashna Zainab and A. Tauheed
P-70
93) New configurations in trebly ionized Bismuth: Bi IV Kumari Arya. Neelam, A. Tauheed
P-71
94) M-shell ionisation in Au and Pb: The Molecular Orbital Picture C.V. Ahmad, R. Gupta, K. Chakraborty, M. Ganguly, D. Swami and P. Verma
P-72
95) Study Of He- and Li-Like Fe, Ni &V Using Multi Channel Doppler Tuned Spectrometer Setup Ranjeet K. Karn , Deepak Swami, Janmejay Mahto, Basu Kumar , C P Safvan and T Nandi
P-73
96) Quantum Phase Transition in Screened Two-electron System A. Sadhukhan, S. Dutta, and J.K. Saha
P-74
97) New Energy levels in the spectrum of singly ionized iodine: I II A Tauheed and Anjum Naz
P-75
98) Ground state energy levels of two-electron ions confined in harmonic potential environment A. Hazra and S. Bhattacharyya
P-76
99) Higher - Component quadrupole polarizabilities of alkaline earth metal ions Mandeep Kaur, Sukhjit Singh, Bindiya Arora and B.K. Sahoo
P-77
100) Ab initio study of the reaction kinetics of X+O3 XO+O2 (X=Cl,Br,I) Gargi Nandi and Tapas Kr. Ghosh
P-78
101) Natural Atomic Charge and Nonlinear Optical Analysis of Some ChargeTransfer Complexes between Chloranilic Acid and Different Donors. Ziya Afroz, Mohd. Faizan and Shabbir Ahmad
P-79
102) Electronic structure study of serotonin molecule: A neurotransmitter Hemlata Bisht, Sandeep Pokharia and Hirdyesh Mishra
P-80
103) Structure, Relative stability and Dissociation pathways of Acrylonitrile and Propionitrile I. Bhattacharyya, A. Sarkar, A. Sadhukhan, S. Bagchi and P. K. Mukherjee
P-81
104) The Bound state Solutions of Schrodinger equation: An Explicit Algorithm Balkrishna Shah
P-82
105) RaH as a promising candidate for P, T violation experiments N. M. Fazil , V. S. Prasanna , K. V. P. Latha , M. Abe and B. P. Das
P-83
PLENARY TALKS
PT1
Highly charged Ion collisions with large molecules: Recent Trends Lokesh C. Tribedi
Tata Institute of Fundamental Research, Colaba, Mumbai 400005, India
Atomic collision physics involving large molecules is closely related to interdisciplinary science. The energy loss of fast ions inside biological matters including water is sensitive to various collision processes: ionization, electron transfer, transfer-ionization which are influenced by different many body processes such as collective excitation apart from size effects or even interference. The e-emission intensity from water and nucleobases, such as, uracil, adenine etc is an important parameter to estimate the radiation damage caused by the fast ions in the context of hadron-therapy and radio-biological modeling. The proposal for using nano-solvated bio-molecule as radio-sensitizer is under investigation. The double differential distributions provide an adequate test to the various theoretical models developed. The recoil-ion measurements for total cross sections of ionization and fragmentation is an important tool to estimate the energy loss of ions in such collisions. A series of studies on the e-DDCS and TCS for water and nucleobases, induced by protons and highly charge C, O, F, or Si ions are used to derive suitable scaling laws. Free C60-molecule plays an important role as a bench- mark system for the study of the many body effect, such as, giant collective plasmon resonance. The plasmon excitation in case of collisions with PAH molecule, e.g. coronene, plays an important role in astrochemistry i.e. UV absorption and also in UV plasmonic devices. Finally nano-solvated bio-molecules are shown to be an important class of systems which may be used as radio-sesitizers in hadron therapy. These set of experiments are relatively new and the proposed influence of the plasmon excitation needs to be investigated. The results from our own experiments using ECRIA and Pelletron at TIFR will be presented along with the results from different groups.
E-mail: [email protected] and [email protected]
PT2
Manipulating Light Quanta Urbasi Sinha
Raman Research Institute, Bengaluru
The Quantum Information and Computing lab at the Raman Research Institute in Bangalore, India has been performing cutting edge research in quantum information processing towards quantum computation, quantum communication as well as fundamental tests of quantum mechanics itself using single and entangled photons. In this talk, I will discuss one of our recent results which is a new insight to a widely used quantum optics phenomenon [1]. The famous Hong-Ou-Mandel two-photon coincidence-visibility dip (TPCVD), which accepts one photon into each port of a balanced beam splitter and yields an equal superposition of a bi-photon from one output port and vacuum from the other port, has numerous applications in photon-source characterization and to quantum metrology and quantum computing. Exceeding 50% two-photon-coincidence visibility is widely believed to signify quantumness. Here, we show theoretically that classical light can yield a 100% TPCVD for controlled randomly chosen relative phase between the two beam-splitter input beams and experimentally demonstrate a 99.635 +/- 0.002% TPCVD with classical microwave fields. We show quantumness emerges via complementarity for the biphoton by adding a second beam splitter to complete an interferometer thereby testing whether the biphoton interferes with itself: Our quantum case shows the proper complementarity trade-off whereas classical microwaves fail. I will also give a general overview of some of our other ongoing experiments and end with our broad vision for the future with our mega project on Quantum Experiments using Satellite Technology (QuEST) in collaboration with the Indian Space Research Organization.
[1]Near-100 % two-photon-like coincidence-visibility dip with classical light and the role of complementarity, S. Sadana, D. Ghosh, K. Joarder, A. Nagalakshmi, B.C. Sanders, U.Sinha, arXiv:1810.01297
PT3
Reliable plasma modeling through electron impact excitation of
inert gases Rajesh Srivastava
Department of Physics, Indian Institute of Technology (I.I.T) Roorkee, Roorkee-247667, India E-mail: [email protected]
The inert gases viz. Ar, Kr and Xe are often added in trace amounts to various plasmas for the optical diagnostic purposes. This technique is known as trace rare gas optical emission spectroscopy (TRG-OES). To develop suitable collisional radiative (CR) models for inert gases and their mixer plasmas at low temperature a large amount of reliable atomic data are required to describe the various atomic and molecular processes occurring in the plasma. The most dominant processes involved in such plasma model are the electron impact excitation and ionization of the inert gases and their accurate cross sections are required. Despite the extensive atomic data reported in the literature on inert gases, there is in general serious lack of electron excitation cross section data for their various fine-structure transitions [1-3]. Our group has been making continuous efforts to produce the reliable cross section data for electron impact excitation/ionization of inert gases viz. Ar, Kr and Xe by using fully relativistic distorted wave (RDW) theory [2-4]. These calculated cross sections are then used to develop the C-R model. The model considers several electron impact fine structure transitions from the ground as well as excited states and their cross sections have been obtained. A review of work on our C-R models that have been developed for Ar, Kr and Xe as well as Ar-O2 and Ar-N2 plasma will be discussed [5-8] and important results will be presented and discussed.
References:
[1] S. Wang, A. E. Wendt, J. B. Boffard, C. C. Lin, S. Radovanov, and H. Persing, J. Vac. Sci. Technol. A, 31 (2013) 021303.
[2] R. A. Dressler, Y. Chiu, O. Zatsarinny, K. Bartschat, R. Srivastava, and L. Sharma, J. Phys. D. Appl. Phys., 42 (2009) 185203.
[3] R. K. Gangwar, L. Sharma, R. Srivastava, and A. D. Stauffer, J. Appl. Phys., 111 (2012) 053307. [4] Dipti, R. K. Gangwar, R. Srivastava, and A. D. Stauffer, Eur. Phys. J. D, 67 (2013) 40244. [5] R. K. Gangwar, Dipti, L. Stafford and R. Srivastava, Plasma Sources Sci. Technol. 25 (2016)
035025. [6] Priti, R. K. Gangwar and R. Srivastava, Physics of Plasmas 25 (2018) 043517. [7] S. Gupta, R. K. Gangwar and R. Sricvastava, Spectrochimica Acta B, 149 (2018) 203. [8] Priti, R. K. Gangwar and R. Srivastava, Plasma Sources Sci. Technol. 28 (2019) 025003.
PT4
Ion beams from plasmas driven by electromagnetic waves: physics
and applications
Sudeep Bhattacharjee
Department of Physics, Indian Institute of Technology – Kanpur [email protected]
With rapid development of basic, applied and inter-disciplinary research in physics and material science, ion beams are becoming an important research tool. Researchers use ion beams having energies ranging from a few eV to some MeV for studying basic and applied aspects of ion-matter interactions. Both low (0 - 5 keV) and medium energy (18 – 30 keV) ion beams, have attracted special attention in recent times, due to their nature of interactions with matter, where the excitation is limited to several subsurface atomic layers. Plasmas have conventionally been employed for generation of ion beams. However, developing plasma sources for ion beams provide critical technological challenges. Often a pencil like beam needs to be extracted thereby demanding that the plasma source be of comparable size. The situation is exacerbated in case of electromagnetic wave driven plasma sources because of geometrical cutoff limitation, which dictates a minimum chamber size for propagation of waves. Additionally, electromagnetic waves are unable to propagate through a plasma having a frequency higher than the wave frequency (commonly known as the density cutoff limitation). The two limitations are often inextricably intertwined and pose considerable challenge in driving electromagnetic waves to create and sustain the plasma [1,2]. The talk will begin with a brief discussion of these limitations and how they may be overcome for realization of intense ion beams. Thereafter, we will present highlights of few research areas where ion beams obtained from plasmas have been applied to modify physical and morphological properties of matter. The first research area is the investigation of surface wettability using noble gas ion irradiation of metallic thin films [3]. This provides a unique method of controlling wettability of surfaces as ion beams do not induce significant surface roughness and chemical heterogeneity. In a second application, it is shown how patterned ion-matter interactions with a suitably chosen ionic species (atomic or molecular), can create localized resistive, conducting or optically active regions in matter [4]. In this case, tuning of sheet resistance and Debye temperatures in metallic thin films have been achieved [5]. As a third example, in the medium energy range where deeper penetration of ion beams is expected, high current (1.5 nA – 1 µA), single focused ion beams of noble gases are employed for large volume milling and rapid creation of microstructures, with wide ranging applications from processing biomaterials for their non-toxicity, to creation of micro-fluidic channels on metallic substrates [6]. The possibility of employing ions of different masses allows a huge variation of momentum transferred to the substrate, so that size controlled microstructures with a large aspect ratio can be fabricated. In conclusion, some future prospects of the research will also be mentioned.
PT4
______________ [1] I. Dey and S. Bhattacharjee, Phys. Plasmas, 18, 022101 (2011). [2] J. V. Mathew, I. Dey, and S. Bhattacharjee, Appl. Phys. Lett., 91, 041503 (2007). [3] S. Chatterjee, S. Bhattacharjee, S. K. Maurya, V. Srinivasan, K. Khare and S. Khandekar, EPL, 118, 68006 (2017). [4] A. Chowdhury, S. Chatterjee, A. Dutta and S. Bhattacharjee, AIP Adv., 4, 127127 (2014). [5] A. Chowdhury and S. Bhattacharjee, J. Phys. D: Appl. Phys., 46, 435304 (2013). [6] S. K. Maurya, S. Paul, J. K. Shah, S. Chatterjee, and S. Bhattacharjee, J. Appl. Phys., 121, 123302 (2017).
INVITED TALKS
IT1
Radiolysis of Nucleobases at Low Temperatures: Radio-
Resistance Measurements
A. N. Agnihotri1,a, G. S. Vignoli Muniz1,2, B. Augé1, P. Ada Bibang1, C. F. Mejía1,3, R. Martinez1,4, M. Bender5, D. Severin5, C. Trautmann5,6, P. Boduch1, A.
Domaracka1, H. Rothard1
1Centre de Recherche sur les Ions, les Matériaux et la Photonique, Normandie Univ, ENSICAEN, UNICAEN, CEA, CNRS, CIMAP-Ganil, 14000 Caen, France 2Instituto de Física da Universidade de São Paulo, São Paulo, SP, CEP 05508-090, Brazil
3Facultad de Ciencias Químicas, Universidad de Cuenca, 010202 Cuenca,Ecuador 4Departamento de Física, Universidade Federal do Amapá, 22453-900 Macapá, Brazil
5GSI Helmholtzzentrum, Darmstadt, Germany 6TU Darmstadt, Germany
a now at: Indian Institute of Technology Delhi, New Delhi, India
*email: [email protected]
Complex organic molecules (COMs) have already been detected in outer space [1]. Laboratory simulations of space conditions involving radiation of icy layers show formation of nucleobases (i.e., adenine, thymine, guanine, cytosine and uracil) [2]. Meteorites found on earth also hint towards their presence in outer space. COMs in space constantly are exposed to radiation (UV, cosmic rays). Laboratory irradiation of COMs allows to determine their radio-resistance, corresponding destruction rates help to estimate their half-life-time in outer space [3]. I will present our studies on radiolysis of nucleobases in solid phase by swift heavy ions at very low temperatures close to those occurring in the outer solar system or dense molecular clouds (~20K). The experiments were performed at GANIL/France and GSI/Germany facilities. Samples of nucleobases were prepared by liquid evaporation and vapor deposition techniques. IR absorption spectra of the samples were obtained in situ, before and after irradiation, with a FTIR spectrometer setup [4].
The evolution of IR absorption bands with the projectile ion fluence allows to deduce apparent destruction cross sections (σd) by a fitting procedure with an exponential decay function. The target samples were irradiated with several projectiles with different electronic stopping power (Se) to obtain the scaling law as a function of electronic stopping power, σd ∝ Sen. Estimations of survival times in the cold universe and comparison to UV radiation will be presented.
Acknowledgement:
We gratefully acknowledge funding from INSERM-INCa (Grant BIORAD), Région Normandie Fonds Européen de Développement Régional-FEDER Programmation
IT1
2014-2020, CAPES-COFECUP French-Brazilian exchange program, Brazilian agencies CNPq (INEspaço and Science without Borders) and FAPERJ, the European Commission, FP7 for RTD Capacities Programme (Contract No. 262010, ENSAR), and the EU’s Horizon 2020 Research and Innovation Programme (grant agreement No. 654002 ENSAR2). ———————————————— [1] K. Altwegg et al, Science Advances : Vol. 2, no. 5, e1600285 (2016). [2] C. K. Materese, M. Nuevo and S. A. Sandford, Astrobiology, Volume 17, No. 8 (2017). [3] G. S. V. Muniz, C. F. Mejía et al, Astrobiology 17:298-308 (2017). [4] E. Seperuelo Duarte, P. Boduch et al, Astronomy and Astrophysics 502 (2): 599–603 (2009).
IT2
Kinetic energy release in dissociation of NH3q+ under ion impact
Pragya Bhatt1*, T. Sairam2 and C. P. Safvan1
1Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067 2Tata Institute of Fundamental Research, Hyderabad 500107
Dissociation of molecules under charged particle impact has been an active field of study. The concerted and sequential dissociation of polyatomic molecules is studied by several researchers. We have studied the dissociation of ammonia under energetic highly charged ion impact. The techniques of recoil ion momentum spectrometry and mutli-hit ion detection are used in unison [1] to obtain the kinetic energy release (KER) in the dissociation of NH3
q+ (q=2,3). The experimental data contain a mixed signature (black curve in Figure 1) for the events arising from the dissociation of doubly and triply ionized NH3. We have used the method of dalitz plot [2] to disentangle the events arising from the symmetric concerted dissociation of NH3
3+ from the rest of the events, see Figure 1.
Figure 1. Kinetic energy release distribution for the dissociation of NH3q+ (q=2,3).
The theoretical ab initio calculations using the quantum chemistry package GAMESS are performed to obtain the possible electronic states for the doubly and triply ionized ammonia molecule. The energy values for these states are found to be in reasonable agreement with our experimental results [3]. These calculations further help in identifying the pathway of dissociation of doubly charged NH3 if it dissociates sequentially.
IT2
________________ [1] P. Bhatt, T. Sairam, A. Kumar, H. Kumar, C. P. Safvan Physical Review A 96, 22710 (2017) [2] R. Dalitz, The London, Edinburgh and Dublin Philosophical Magazine Journal of Science 44, 1068 (1953) [3] P. Bhatt et al to be communicated.
IT3
Photo-absorption studies on gas phase biological chromophores Jyoti Rajput
Department of Physics and Astrophysics, University of Delhi, Delhi
Photo-absorption studies on gas phase biological chromophores is an important step in the "bottom-up" approach towards understanding the role that these special molecules play in biological functions. We have measured the photo-absorption spectra of several model biological chromophores using the technique of action spectroscopy and by employing an electro-spray ion source, an electrostatic storage ring and nano-second lasers. A discussion on the experimental results will be presented.
IT4
Studying ion dynamics with Electrostatic Ion Beam Trap K. Saha1,2, V. Chandrasekaran2,3, R. K. Gangwar2,4, A. Prabhakaran2,5, O. Heber2,
M. A. Iron6, M. L. Rappaport7 and D. Zajfman2 1 Currently at Department of Physics, Indian Institute of Technology, Dharwad, India.
2Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot, Israel. 3Currently at Vellore Institute of Technology, Vellore, India.
4Currently at Department of Physics, Indian Institute of Technology, Tirupati, India. 5Currently at Pacific Northwest National Laboratory, Washington, USA.
6Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel.
7 Department of Physics Core Facilities, Weizmann Institute of Science, Rehovot, Israel.
The electrostatic ion beam trap (EIBT) is a unique ion trapping and storage device. The EIBT is a compact device which uses electrostatic fields to trap ion beams with energies of several keV. The ions are trapped in an oscillatory motion in a field free region between two mirror electrodes of EIBT by application of appropriate potentials. Since its development by Zajfman et. al. [1,2] in the late 1990s, the EIBT have been employed to perform various studies on trapped ion beams. When coupled with a laser, the EIBT becomes capable of revealing intricate dynamics that occur in laser-excited molecular or cluster ions. Further, the trapped ions in the EIBT, upon certain trapping conditions, also exhibit interesting dynamics that can have potential applications in mass spectrometry and cold collision physics.
Figure 1. Schematic of the electrostatic ion beam trap.
Here, some of the recent studies that have been performed using the EIBT at the Weizmann Institute of Science will be presented. We observed that trapped ion bunch in the
IT4 EIBT exhibit quadrupole oscillations within the bunch [3]. Further, application of an autoresonance force
in certain configuration to the trapped ion bunch lead to cooling of the translation degrees of freedom of the ion bunch [4]. Also, we were able to decipher an ultraslow isomerisation process in laser excited trapped C60
- cluster for the first time [5]. Energy analysis of vibrationally autodetached electrons from laser excited trapped C5
- was also performed with a newly designed Velocity Map Imaging (VMI) spectrometer that was integrated to the EIBT [4]. In our experiments we were able to track delayed electron emission for a long duration after laser excitation for the first time. ________________
[1] D. Zajfman et al., Phys. Rev. A 55, R1577 (1997). [2] M. Dahan et al., Rev. Sci. Instrum. 69, 76 (1998). [3] K. Saha et al., Rev. Sci. Instrum., 87, 113302, (2016). [4] R. K. Gangwar et al., Phys. Rev. Lett., 119, 103202, (2017). [5] K. Saha et al., Nature Comm., 9, 912, (2018). [6] K. Saha et al., Rev. Sci. Instrum., 88, 053101, (2017).
IT5
The Cryogenic Storage Ring CSR
P. M. Mishra1,2* and the CSR team2 1AMO Physics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan (present affiliation) 2 Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
The Cryogenic Storage Ring (CSR) [1] with circumference of 35 m, located at Max-Planck-Institut für Kernphysik in Heidelberg is an ideal experimental setup to perform collision studies of photons and cold electrons as well neutrals with stored molecular ions of kinetic energies between 20-300 keV. The cryogenic temperature of about 6 K offers unique storage capabilities in extreme vacuum conditions of below 140 rest-gas particles per cm³ and almost vanishing blackbody radiation. An electron cooler (ecool) is installed which uses photocathode to produce cold electrons. These cold electrons can further reduce the momentum spread of stored ion beam upon interaction. A tunable optical parametric oscillator (OPO) laser system allows photon interaction studies from the ultraviolet (225 nm) to the infrared (2600 nm) regime. The CSR is equipped with two independent ion source platforms which can deliver ions upto energy 60 and 300 keV. The low energy platform would be used to produce neutral beams from photo-detached negative ions. Whereas the 300-kV platform presently contains a metal ion sputter source, a Penning source and an electron cyclotron resonance source; extension by a laser vaporization and an electrospray ionization ion source is in progress. The ion orbit comprises four 2 m long, field-free straight sections for collision experiments. The entire facility enables to perform photodissociation, electron-ion recombination, and ion-atom interaction studies with ro-vibrationally cooled stored positive and negative ions as well as clusters and highly charged ions. Further experiments aim to study decay rates of metastable ions and radiative lifetimes. The first experimental results, machine characteristics as well as future experimental possibilities of this unique infrastructure will be discussed [2, 3].
IT5
Figure 1. The layout of CSR (closed orbit circumference: 35 m) showing ion optical elements and experimental probes.
________________
[1] R. von Hahn et al., Rev. Sci. Instrum. 87, 063115 (2016). [2] A. O’ Connor et al., Phys. Rev. Lett. 116, 113002 (2016). [3] C. Meyer et al., Phys. Rev. Lett. 119, 023202 (2017).
IT6
A global search for an unlimited, sustainable energy source for future generations
R. Shanker
Atomic Physics Laboratory, Physics Department, Institute of Science, Banaras Hindu University, Varanasi-221005
E-mail address:[email protected]
There has been a global interest to seek an energy source which is unlimited, safe and eco-friendly. This talk is intended to address the same objective with on-going efforts to achieve this goal. A brief account of the type of energy sources that are available to human kind will be given and discussed. The idea of creating a ‘small’ or ‘baby’ SUN on Earth will be discussed at length. The current activities going-on to realise this idea around the world has been initiated by constructing a giant machine called ‘ITER’ which is being installed in southern France. Some important scientific and technological aspects of this machine will be presented and discussed. Related to the functioning of this machine and to the kind of materials to be used in the plasma facing wall of the plasma vessel, a few recent experiments have been conducted in our atomic physics laboratory at BHU and the obtained are presented and discussed [1-2]
[1]. S. Kumar, P. Bhatt, B.K. Singh, A. Kumar, R. Shanker An experimental set up for studying the fusion edge plasma facing materials using TOF mass spectrometry, International Journal of Mass Spectrometry 385 32-41(2015) [2]. S.Kumar, P.Bhatt, A.Kumar, B.K.Singh, B.Singh, S. Prajapati, R. Shanker, Measurement of ion species produced due to bombardment of 450 eV N2
+ ions with hydrocarbons-covered surface of W: Formation of tungsten nitride. Nuclear Instruments and Methods in Physics Research B, 380 50–56 (2016)
IT7
Study of atom localization in different atomic system via spatial dependent probe absorption
Ajay Wasan
Department of Physics, Indian Institute of Technology Roorkee
In recent years, there has been great interest in the interaction of an atomic ensemble with external fields from both theoretical and experimental viewpoints. In last two decades, advances in experiments have led to the observation of new sorts of atomic media such as Bose-Einstein condensate (BEC), a single atom in a trap and a quantum qubit for quantum computing. These experiments have opened new prospects of studying fundamental properties of atomic interaction in the condensed matter, ultracold particle collisions and quantum entanglement. The success of these works was initiated by the presence of atomic transitions driven by optical laser sources. This interaction has quantum nature which also appears in electromagnetically induced transparency and coherent population trapping. These effects has been explained theoretically using density matrix formalism. We have extended same density matrix formalism to explain atom localization in two different atomic system [1, 2] via spatial dependent probe absorption. Due to position dependent interaction of the atom in the standing-wave field, the absorption spectra of the probe field provide the precise information about atom localization in a subspace of one wavelength. While numerically solving the density matrix equations, various kinds of localization patterns are obtained in two- and three-dimensions atom localization. We have shown that the maximal detection probability of finding atom at a position, i.e., unity can be obtained in a quadrant by proper adjusting the fields’ parameters. References:
[1] Neeraj Singh and Ajay Wasan, “High-precision two-and three-dimensional atom localization via spatial dependent probe absorption in a closed-loop M-type atomic system”, J. Opt. Soc. Am. B 35, 1318 (2018)
[2] Neeraj Singh, Raj Kumar and Ajay Wasan, “Effect of nearby levels on atom localization in the Ξ atomic system via spatial dependent probe absorption”, OSA continuum 2, 862 (2019)
IT8
Polarization Rotation in a Coherent Atomic Medium
Arpita Das1, Bankim Chandra Das1, Dipankar Bhattacharyya2, Shrabana Chakrabarti1 and Sankar De1
1Saha Institute of Nuclear Physics, HBNI, 1/AF, Bidhannagar, Kolkata - 700064, India
2Department of Physics, Santipur College, Santipur, Nadia, West Bengal, 741404, India Polarization rotation of the probe beam in electromagnetically induced transparent (EIT) Rubidium (87Rb) atomic medium was measured by polarimetry technique [1]. A linearly polarized probe and a circularly polarized pump beam were co-propagated through the atomic medium. This generated an anisotropy towards the refractive index of the medium which creates optical birefringence and leads to a rotation in the plane of polarization of the probe beam. In our experiment, we have calculated the angle of rotation from the slope of the polarization rotation spectra. We observed that the angle of polarization rotation of the probe beam depends non-linearly on the pump beam intensity. We have also studied how the angular mismatch between the probe and the pump fields affect the anisotropic behaviour of the atomic medium. To understand the phenomena and get the probe coherence term, we have solved the Liouville equation analytically under steady state condition with the first order perturbation for the probe beam. We found that a mismatch in the population distribution led to the rotation of the plane of polarization. Since we got sharp dispersion signal at the EIT position, this signal can be used in robust optical locking technique. Moreover, this rotation signal is highly sensitive to the magnetic field, thus having application in precision magnetometry.
Reference: [1] Arpita Das, Bankim Chandra Das, Dipankar Bhattacharyya, Shrabana Chakrabarti, and Sankar De, Polarization rotation with electromagnetically induced transparency in a V-type configuration of Rb D1 and D2 transitions, J. Phys. B: At. Mol. Opt. Phys. 51, 175502 (2018).
IT9
Density functional theory based study of a two-dimensional gas of dipolar fermions in a harmonic trap
Arup Banerjee1,2 and Amit Das1
1 Raja Ramanna Centre for Advanced Technology, Indore 452013, 2 Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai
400094
.
Recently ultra-cold dipolar Fermi gases of atoms and molecules have been successfully created and this has engendered a new class of many-body systems with long-range interactions. The characteristic properties of dipolar Fermi gas are distinctly different from that of an electron gas and usual Fermi gas made of non-dipolar atoms due to the long-range anisotropic nature of the interaction between two dipoles. The dipolar Fermi gases have been realized experimentally by using various atomic species with large magnetic moment as well as heteronuclear polar diatomic molecules with large electric dipole moment. Dipolar gases in three-dimensions are plagued by instabilities due to combination of partly attractive nature of the dipolar interaction and collisional losses. The lifetime and stability of dipolar Fermi gas consisting of heteronuclear molecules with permanent dipole moment has been successfully enhanced by confining the gas in two-dimensions. Such two-dimensional (2D) dipolar Fermi gases provides an opportunity to explore Fermi systems with strong correlations in a controlled manner. The ground state properties of both homogeneous and harmonically trapped 2D dipolar fermions have been theoretically studied by employing various theoretical methods ranging from Hartree-Fock formalism to Density functional theory (DFT). The accuracy of DFT based results crucially depends on the approximate forms of the exchange and correlation energy functionals employed for the calculations. In this presentation we will discuss and assess the accuracy of DFT based method for the calculation of ground state properties of a spin-polarized dipolar Fermi gas trapped in a 2D harmonic oscillator potential.
IT10
Multielectron processes in van der Waals aggregates hosted in private quantum fluid cryostats unraveled by coincidence
spectroscopy
Sivarama Krishnan*
* Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
With the advent of advanced current and next generation light sources such as free-electron lasers and attosecond light pulses in the extreme ultraviolet (EUV), soft- and hard-xrays, the need to understand multielectron processes in individual atoms and atomic aggregates becomes increasingly important. These processes have also been recognized as primary and critical steps radiation damage in large, yet loosely bound, molecular edifices such as the primordial DNA molecules. In particular, van der Waals aggregates in the form of rare-gas clusters doped with other atoms or molecules present an ideal test case for unearthing and understanding multielectron quantum dynamics which ensues after a single photon, often in the EUV or soft-xray, is absorbed. We use He nanodroplets, quantum fluids in a superfluid state as ‘private cryostats’ which host alkali clusters on them. Following the absorption of a soft xray photon by the He host, intriguing quantum dynamics, hitherto unseen and, perhaps, unforeseen occurs. In this talk, we will present the results of recent work done at the Elettra synchrotron using electron-ion multiple coincidence spectroscopy along with our current understanding of the underlying mechanism of the quantum dynamics. This work motivates further investigations using free-electron lasers and attosecond pulses in such systems.
References 1) D Buchta, S R Krishnan, et al., The Journal of chemical physics 139 (8), 084301 (2013). 2) ibid., The Journal of Physical Chemistry A 117 (21), 4394-4403 (2013) 3) A C LaForge et al., Physical review letters 116 (20), 203001. 4) Averbukh, V., Imke B. M, and L. S. Cederbaum, Physical review letters 93.26 (2004): 263002. 5) Santra, Robin, et al. Physical review letters 85.21 (2000): 4490. 6) Shcherbinin, M., et al. The Journal of chemical physics 150, 044304 (2019). 7) Y. Ovcharenko et al., Phys. Rev. Lett. 112, 073401 (2014)
IT11
Ionization asymmetries and molecular orientation in two-color laser strong fields
N Bhargava Ram*
1Department of Physics, IISER - Bhopal, India *[email protected]
Molecular ionization rates in strong fields is requisite parameter to understand many processes arising out of strong field ionization viz. High-harmonic spectroscopy, laser-induced photoelectron rescattering etc. Accurate theories are unavailable and so is experimental data except for a few polar molecules. The intrinsic multi-electron effects makes it challenging to accurately measure or estimate the ionization rates. One of the ways to understand the molecular-axis dependent ionization rates experimentally by employing phase-locked two-color laser fields. It has been shown by angular distribution measurements that one can field-free molecular samples in the gas phase with high degree of orientation and can also be used to determine orientation-dependent ionization rates [1, 2]. In my presentation, I will present details of the two-color orientation and ionization asymmetries in the case of symmetric tops, specifically the methyl halide molecules (CH3X, with X = F, Cl, Br or I). [1] S. De, I. Znakovskaya, D. Ray, F. Anis, N. G. Johson et al., Phys. Rev. Lett. 103, 153002 (2009). [2] S. G. Walt, N. B. Ram, A. Conta, O. Tolstikhin, L. B. Madsen, F. Jensen and H. J. Worner, J. Phys. Chem. A 119, 11772 (2015).
IT12
Wakefield generation and the formation of EM soliton in relativistic plasmas
S. Roy, D. Chatterjee and A. P. Misra*
Department of Mathematics, Visva-Bharati (A Central University), Santiniketan-731 235, WB, India
Based on a relativistic fluid model coupled to the Maxwell's equations, we investigate the nonlinear interaction of high-frequency linearly polarized electromagnetic (EM) waves and low-frequency electron plasma oscillations that are driven by the EM wave's ponderomotive force in a relativistic plasma with degenerate electrons. The relativistic degeneracy parameter is shown to play a vital role for the transition from the wakefield generation to the soliton formation. The energy loss of the EM pulse due to the wakefield generation is also calculated. The unique features of the EM solitons and wakefields are also studied. The results should be useful for understanding the salient features of enhanced density fluctuations and the dynamics of X-ray pulses that may emanate from compact astrophysical objects. The results can also be useful in the next-generation highly intense laser produced solid density compressed plasma experiments.
IT13
Low energy free electron induced chemistry Vaibhav S. Prabhudesai1
1 Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai India
Chemical reaction is understood to be a process of making and/or breaking bonds. In many cases, where a catalyst plays a role, it is the addition of extra electron from or to this entity that triggers the chemical reaction. What would happen when an extra free electron is added to the system from outside instead of having a catalyst? This addition of electron, depending on its energy and type of molecule present, can result in the formation of a negative ion. As the kinetic energy of the incoming electron is dumped into the molecule, this results in the formation of excited negative ion, which is also known as negative ion resonance (NIR). If this NIR survives autodetachment, it may result in bond breaking known as dissociative electron attachment (DEA). We have shown that the DEA process exhibits site selectivity in bond breaking that depends on the functional group present in the molecule [1]. On the other hand, the parent negative ion formation by the electron attachment, can also lower the barrier for a specific reaction path, which can be as simple as dissociation of multiple bonds. If during this process the excess electron leaves the system, the final products would be only neutral fragments as against an anion and one or more neutral fragments obtained in DEA. This new mechanism is known as bond breaking by catalytic electron (BBCE), which was predicted recently [2]. Here, the extra free electron acts as a catalyst. In yet another possibility, the electron impact can cause dissociation in the neutral molecule, which can lead to the formation of radicals. These radicals, on further encountering other species, can trigger a chemical reaction. All these channels show that there are many possibilities in low energy free electron induced chemistry. In this talk, I will discuss these possibilities along with our recent findings of catalytic action of free electron [3] as well as low energy electron induced dissociation that leads to the C-H activation in organic molecules [4], which is one of the most sought after chemical reactions. ________________ [1] V. S. Prabhudesai, A. H. Kelkar, D. Nandi and E. Krishnakumar, Phys. Rev. Lett. 95, 143202 (2005). [2] D. Davis, V. P. Vysotskiy, Y. Sajeev, and L. S. Cederbaum, Angew. Chem. Int. Ed. 50, 4119 (2011). [3] D. Davis, S. Kundu, V. S. Prabhudesai, Y. Sajeev, and E. Krishnakumar, J Chem. Phys., 149, 064308 (2018). [4] S. Kundu, V. S. Prabhudesai and E. Krishnakumar, J Phys Chem C, 121, 22862 (2017).
IT14
Electron driven DEA study with targets of applied interest Minaxi Vinodkumar1*, Hitesh Yadav1, 2 and P. C. Vinodkumar1
1 Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Gujarat, India 2 V. P. & R. P. T. P. Science College, Vallabh Vidyanagar, Gujarat, India
Electron impact scattering studies have history of decades, still the development in the instrumentation and theoretical approach to study the different phenomenon particularly at low energy are difficult.
Figure 1 DEA cross sections of Br-
Dissociative electron attachment (DEA) process, despite being an important phenomenon in the field of plasma physics [1], environmental science [2] and radiation damage, finds sparse attention by theoretical groups. On the contrary, substantial progress has been made on experimental studies of this process of non-halogenic atoms/molecules, largely because of new experimental techniques involving electron beams with high energy resolution. We have used R-matrix [3] method for computation of eigen-phases through which resonance width and resonant energy are computed
IT14
at low energies. These are important inputs for computing the DEA cross sections via. Quantemol-N software [3,4] using two theoretical approaches i.e. Static Exchange Plus Polarization (SEP) and Configuration Interaction (CI). As a sample result, we present here DEA study for Br2 molecule. Fig. 1 shows the results of the DEA of Br- (anion formation) from Br2. The present theoretical results are compared with lone experimental result of Kurepa et al [5]. The detailed results and discussions will be carried out at the conference. Dr. Minaxi Vinodkumar acknowledges DST-SERB, New Delhi for Major research project [EMR/2016/000470] for financial support under which part of this work is carried out. [1] L. G.Christophorou and J. K.Olthoff, J. Phys. Chem. Ref. Data, 28, 131-169 (1999). [2] Q. B. Lu and L. Sanche,Phys. Rev. Lett. 87, 078501 (2001). [3] J. Tennyson, Phys. Rep., 491, 29-76 (2010). [4] H. Yadav, M. Vinodkumar, C. Limbachiya and P. C. Vinodkumar, J. Phys. B: 51, 045201 (2018). [5] M. V. Kurepa and B. S. Belic, J. Phys. B: 11, 3719 (1978).
IT15
Turbulance in space plasmas
Supratik Banerjee
Dept. of Physics, Indian Institute of Technology Kanpur [email protected]
Space plasmas (the solar wind, magnetospheric plasmas) are different from laboratory plasmas in various aspects. In this talk, I shall briefly give an introduction to the space plasmas in terms of different characteristic parameters (plasma frequency, Debye length, ion inertial length, plasma beta etc.). This introduction will be followed by a schematic description of turbulence in such plasmas. This part will be elaborated by the help of different research works dedicated to understand the basic properties of solar wind turbulence. Finally, I shall talk a bit about my research work on the effect of compressibility in the solar wind turbulence (Banerjee et al., ApJ, 2016).
IT16
Multiwavelength imaging and numerical simulation of solar coronal transients
Ramit Bhattacharyya Udaipur Solar Observatory
Physical Research Laboratory
Solar coronal transients are spectacular events where magnetic energy gets converted into heat and kinetic energy of the plasma accompanied with a rearrangement of magnetic field lines. Understanding the physics of the transients is not only of fundamental interest but also important from the perspective of space-weather. The large energetic events like solar flares and Coronal Mass Ejections (CMEs) catapult energetic particles and plasma into the interplanetary medium which can adversely affect the space industry. Present research indicates the phenomenon of magnetic reconnection to be responsible for the transients which, will be explored by a combination of multiwavelength observations of the Sun and related numerical simulations.
ORAL PRESENTATIONS
OP1
Dynamics and control of photon transport in coupled cavities
Nilakantha Meher
Department of Physics, Indian Institute of Technology Kanpur, Kanpur UP 208016, India Email: [email protected]
Controlled transfer of photonic states is essential for implementing quantum information protocols in cavity arrays [1]. A basic requirement for effecting such a transfer is to tailor the system parameters such as the cavity frequencies, couplings, detunings, etc. Moreover, cavities containing atom or nonlinear medium can be considered that have additional control parameters, namely, the atomic state and nonlinearity. Controlled dynamics of photon transfer in a cavity array by appropriate choices of these parameters is established [2].Perfect transfer of a single photon in an array is not possible if the cavity couplings are homogeneous. A duality relation between two systems, namely, N − 1 photons in two coupled cavities and a single photon in N cavities is employed to arrive at the required coupling strengths and nonlinearities in the array so that controlled and perfect photon transfer is possible between any two cavities in the array. Every transition in the two-cavity system has a dual phenomenon in terms of photon transport in the array. The condition for perfect transfer of photon enables transfer of photonic qubit between any two cavities in the array. Possibility of high fidelity generation of generalized NOON states in the two coupled cavities, which are dual to the Bell states of the photon in the cavity array, is established.Dynamics of photon transfer in dissipative structures is another topic of interest [3]. A system of two coupled cavities connected between two thermal reservoirs is considered. Embedding a dispersively interacting single atom in any one of the cavities brings a controllable flow of heat energy through the array. The thermal current through a system of two coupled cavities containing a single atom depends on the atomic state. By switching the state of the atom from its excited state to the ground state, the system changes from a thermal conductor to an insulator.In addition, by properly tuning the atomic state and system-reservoir parameters, direction of current can be reversed. It is shown that a large thermal rectification is achievable in this system by tuning the cavity-reservoir and cavity-atom couplings.
[1] A. Reiserer and G. Rempe, Rev. Mod. Phys. 87, 1379 (2015). [2] N. Meher, S. Sivakumar and P. K. Panigrahi, Scientific Reports 7, 9251 (2017). [3] N. Meher and S. Sivakumar, arXiv: 1804.01897 [quant-ph].
OP2
Photoabsorption studies of nitromethane using synchrotron radiation Aparna Shastri1,2*, Asim Das1,2, Sunanda K.1 and B.N. Raja Sekhar1,2
1Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India 2Homi Bhabha National Institute, Anushaktinagar, Mumbai-400 094, India
Organic compounds containing the nitro (NO2) group have physical and chemical properties which make them amenable for applications like propellant ignition, combustion, explosive materials, etc. Additionally some of them may also play a role in atmospheric pollution. As a prerequisite to investigating the complex reaction mechanisms involved in detonation/combustion processes and atmospheric chemistry, a good understanding of their electronic structure and spectra is essential. Nitromethane (CH3NO2), being the simplest organic nitro compound is a prototype of this important class of compounds which is widely used as a synthetic reagent, solvent and also as an explosive [1,2]. From a fundamental point of view, nitromethane presents an interesting case with an unusually high dipole moment (3.46 D) and geometrical structure which strictly speaking belongs to Cs, but can be approximated to C2V. Despite these strong motivating reasons for understanding the electronically excited states and spectroscopy of nitromethane, so far, very few experimental and theoretical studies in this direction have been reported in literature [1-3].
Figure 1. A portion of the VUV photoabsorption spectrum of nitromethane In the present work, we report UV-VUV photoabsorption studies of nitromethane performed using the Photophysics beamline at Indus-1 synchrotron radiation source, RRCAT, Indore [4]. A part of the observed VUV absorption spectrum is shown in Figure 1. Spectral analysis and interpretation is carried out with the help of quantum chemical calculations on electronically excited states of nitromethane using the GAMESS (US) suite of programs [5]. Details of the experimental and theoretical procedures used, results obtained and interpretation of spectral features vis-a-vis the theoretical predictions will be discussed.
OP2
______________ [1] I.C. Walker, M.A.D. Fluendy, Int. J. Mass. Spect. 205, 171 (2001). [2] D.J. Goebbert, K. Pichugin, A. Sanov, J. Chem. Phys. 131, 164308 (2009). [3] J.F. Arenas, J.C. Otero, D. Pelaez, J. Soto, J. Chem. Phys. 119, 7814 (2003). [4] N.C. Das, B.N.R. Sekhar, S. Padmanabhan, A. Shastri, S.N. Jha, S.S. Bhattacharya, S. Bhat, A.K. Sinha,
V.C. Sahani, J. Optics (India) 32 (4), 169 (2003). [5] M.W. Schmidt, K.K. Baldridge, J.A. Boatz, S.T. Elbert, M.S. Gordon, J. H. Jensen, S. Koseki, N.
Matsunaga, K.A. Nguyen, S. Su, T.L. Windus, M. Dupuis, J.A. Montgomery, J. Comp. Chem 14 (11), 1347 (1993).
OP3
Post ionization alignment effect in O2+
Arnab Sen1, T. Sairam2 , B. Bapat1, R. Gopal2* ,V. Sharma3*
1Indian Institute of Science Education and Research, Pune, Maharashtra, 411008, India 2Tata Institute of Fundamental Research, Hyderabad, 500107, India
3 Indian Institute of Technology, Hyderabad, 502285, India
*email address: [email protected], [email protected]
Interaction of intense laser pulses with even simple molecules involves intriguing processes such as bond-softening, bond hardening, resonance–enhanced ionization etc. Under moderately intense (~1013 W/cm2), 30 fs laser pulses, the ionization of O2 is followed by dissociation of the molecular ion to an ion and a neutral fragment. In experiments, using a newly developed ion imaging spectrometer [1] we have obtained the 3D momentum distribution of the ionic fragment. From the kinetic energy distributions, we delineate the dissociation pathway [2,3] involving laser dressed excited states of O2
+. We show clear evidence that the angular distributions obtained can be described by invoking the so-called post ionization alignment model [4]. In this model, the molecular ion aligns to the polarization axis of the laser field as a result of a rotational impulse imparted by the interaction of the laser electric field with the dipole of molecular ion. Our semi-classical calculations, which capture this rotation, have striking agreement with the experimental results.
________________
[1] R.Gopal, A Sen, SR Sahu, AS Venkatachalam, M Anand, V Sharma, Rev. Sci. Instrum. 89, 086107 (2018). [2]A.M. Sayler et.al PR. A: 75,063420(2007). [3] M. Zohrabi et.al PR. A: 83,053405(2011). [4] X.M. Tong et.al J. Phys. B: At. Mol. Opt. Phys. 38, 333(2005).
OP4
Study of multiply charged Argon recoil ions formed under 3.5 keV electron impact using electron-ion coincidence technique
Sunil Kumar1, 2, Suman Prajapati1, Bhupendra Singh1, Manish Kumar Singh3, B.K.Singh1, R.Shanker1
1Atomic Physics Laboratory, Department of Physics, Institute of Science, Banaras Hindu University, Varanasi-221005
2Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot, Israel-76100
3Department of Physics, Indian Institute of Technology, Banaras Hindu University, Varanasi-221005
Email address: [email protected]
The mechanism of recoil ions formation has been investigated by many groups under charged particle collision during the past decades. In such collisions, the target atoms are left in an ‘electronically hot’ state, but ‘translationally cold’ recoil ions [1]. The physics of recoil ions has played an important role in various fields, such as, fusion plasma studies, development of vacuum ultra-violet and x-ray laser systems, study of static and dynamic behaviour of atmospheres, precision wavelength spectroscopy and design of parasitic sources of bare and few electron low energy ions and many others.
In the present work we have employed energy selected electron-ion coincidence technique to study the decay pathways of 2p- hole created under impact of continuous electron beam having kinetic energy 3.5 keV. Several non-radiative inner shell transitions, e.g., Auger process, Auger cascade transitions, Coster-Kronig, auto-ionization, shake processes etc. have been investigated which lead the formation of multiply charged Argon ions with charge states from Ar+ to Ar4+ for 18 energy selected electrons. The relative correlation probability for the formation of various charge states of Argon ions has been determined experimentally for the selected electron energies range [2]. Several other aspects and implications for the formation of multiply charged Ar ions using our recently developed experimental set-up [3] have been obtained, in particular, information with regard to the respective energy levels diagram has been presented and discussed. The experimental relative correlation probability for the formation of various charge states of Argon ions produced in 3.5keV electron impact with free Argon atoms is shown in Figure 1.
OP4
Figure 2. Relative correlation probability of Argon recoil ions formation produced in the collision of 3.5keV electron impact [3].
References:
[1] C.L. Cocke Phys. Rev. A. 20 (1979) 749. [2] Sunil Kumar et al. EPJD, (2017) 71: 53. [3] Sunil Kumar et al. Indian Journal of Physics , (July 2017) 91(7):721–72.
OP5
An extensive study of Pyrrole biomolecule through electron
scattering Hardik Desai1*, Minaxi Vinodkumar2,Hitesh Yadav3 andP.C. Vinodkumar3
1 Sheth P.T. Mahila College of Arts &Science, Vanita Vishram, Surat, Gujarat, India - 395001 2V P & R P T P Science College, Vallabh Vidyanagar, Gujarat, India - 388 120
3Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Gujarat, India - 388120
As high energy ionizing radiation is widely used in biomedical applications, both for diagnosis and treatment, the production of abundance of low energy electrons through high energy radiation leads to the single and double strand breaks in the DNA [1] is well established fact now. This has induced recent interest on electron-scattering studies in the investigation of biologically important compounds likePyrroles which are found in a variety of biological milieus, as parts of cofactors and natural products. In the low energy regime of the electron impact, incident electrons are captured by the target potential to form the shape resonance leading to the Dissociative Electron Attachment (DEA) Phenomenon [2-3]. Discovery of DNA strand breaking by Boudaiffa et.al. [1] and striking experimental evidence that radiation damage could be mediated by DEA at low energies provided by Sanche and co-workers [4] have prompted us to take up the DEA studies of DNA and its prototypes. Pyrrole is a biomolecule prototype of DNA components baring the great importance for an establishment of radiation damage model for living tissues. Thus, to design the radiation interaction model and to study the energy deposition in living matter, comprehensive data set for basic constituents of biological systems, from near thermal energy range (meV) up to very high (MeV) energies are well in demand.The DEA phenomenon is important from the point of view, eying the fragmentation and local chemistry of the targets. Since the unquestionable interpretation of data concerning electron-assisted processes with condensed bio-matter is difficult, accurate quantities describing particular electron collision events with biologically important compounds in gas-phase or with their simple analogues are very helpful. Comprehensive low energy (0.01 to 20 eV) electron impact scattering study is carried out for pyrrole molecule focusing the dissociation by transient negative ion formation. We have used R-matrix method [5,6] for low energy computation of eigen-phases through which resonance width and resonant energy are computed which are important inputs for computing the DEA cross sections. Moreover low energy scattering calculations are also carried to compute the target properties, Momentum transfer Cross sections, Differential Cross Sections, Excitation Cross Sections and Rate coefficients. ________________ [1] B. Boudaiffa et. al., Science 287, 1658 (2000). [2] J. Munro et. al., J. of Phys: Conference Series, 388, 012013 (2012). [3] H. Yadav et al.,Molecular Physics 115, 952 (2017). [4] L. Sanche, Eur. Phys. J. D,35, 367 (2005). [5] J. Tennyson, Physics Reports 491, 29 (2010).
[6] M. Vinodkumar et al., Phys. Rev. A 93, 012702 (2016).
OP6
Particle balance in a plasma confined in a dipole magnetic field
Anuj Ram Baitha, Sargam, Ayesha Nanda and Sudeep Bhattacharjee*
1Department of Physics, Indian Institute of Technology - Kanpur, Kanpur 208016, India *[email protected]
Plasmas confined by dipole magnetic fields have unique transport properties that govern different plasma dynamics both in laboratory and space plasma experiments [1 - 3]. In a plasma which is at steady state, there is usually a balance between generation and loss processes occurring in the plasma. The loss processes are primarily governed by diffusion, recombination and Bohm losses through the sheath [4]. In this work, particle balance in a plasma confined in a dipole magnetic field is investigated through experiments and theory. A microwave plasma experiment has been designed by employing a cylindrical permanent magnet (NdFeB) which is water cooled [5]. The plasma is generated by electron cyclotron resonance (ECR) heating of microwaves (2.45 GHz) and is operated in a continuous mode. While most of the earlier experiments have been large, employing superconducting coils and in the pulsed mode [1 - 3], the present experiment with a single permanent magnet allows investigations in a continuous mode of operation, so that steady state regimes can be achieved and investigated.
Visual observations of the plasma indicate that the plasma is created around the magnet and has a structure similar to our magnetosphere; one can see occurrence of alternate bright and dark regions similar to the radiation belts [5]. Experiments have been carried out to measure the plasma density and temperature at different polar angles. Assuming azimuthal symmetry, a mathematical model for particle balance has been constructed in spherical polar coordinates by taking the dipole variation of the magnetic field in account. The resulting particle balance equation is solved analytically to determine the production and loss rates as a function of radial distances and neutral pressures at different polar angles. Results demonstrate production of hot plasma near the dipole magnet and subsequent decrease in the plasma production rate from magnet surface toward the edge of the vacuum chamber, in accordance with the experimental results. The production and loss rates are higher in equatorial plane and increases with increase in neutral pressure. The summarized results as a function of distance, neutral pressures at different polar angles will be presented in the conference. ________________ [1] A. C. Boxer, R. Bergmann, J. L. Ellsworth, D. T. Garnier, J. Kesner, M. E. Mauel and P. Woskov, Nature Phys. 6, 207(2010). [2] Y. Chen, G. D. Reeves and R. H. W. Friedel, Nature Physics 3, 614 (2007). [3] Z. Yoshida, H. Saitoh, J. Morikawa, Y. Yano, S. Watanabe and Y. Ogawa, Phys. Rev. Lett. 104, 235004 (2010). [4] T. A. Santhosh Kumar, S. K. Mattoo and R. Jha, Phys. Plasmas 9, 7 (2002). [5] A. R. Baitha, A. Kumar and S. Bhattacharjee, Rev. Sci. Instrum., 89, 023503 (2018).
POSTER
P-01
ION INDUCED DISSOCIATION OF METHANE
Diksha Garg1,a , C.P. Safvan2, Jyoti Rajput1,b
1Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India
2Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi 110067, India [email protected]
We have studied the dissociation of isolated methane molecules using the technique of Recoil Ion Momentum Spectroscopy (RIMS). The methane molecules (CH4) are ionized using energetic (keV) beams of highly charged ions. The interaction of projectile ions and neutral methane molecules results in the emission/capture of electrons and the formation of molecular ions. The molecular ions are unstable and dissociate into fragment ions. These recoil fragments are extracted in a time of flight mass spectrometer and are collected in coincidence with charged exchanged projectile. Through this spectroscopy, the coincident time of flight and position of recoil ions and projectile ion can be measured simultaneously. In this experiment, the supersonic gas jet of methane is positioned in a mutually perpendicular direction with the projectile ion beam and the time of flight axis. Micro Channel Plate (MCP) detectors are used to detect the recoil ions and projectile ions.
P-01
Figure 1. Kinetic energy release for dissociation of doubly charged methane. The data was collected in coincidence with single captured projectile.
The experiment was done for two projectile ions, Argon (Ar9+) and Nitrogen (N3+) moving with the same velocities (0.37 atomic units). In this presentation, the KER of the complete two body dissociation channel: CH4
2+ →
CH3+ + H+ for the two
projectile ions will be reported. The recoil ions were collected in coincidence with a projectile which has retained a single electron after the interaction.
P-02
Design and Implementation of Post Collision Charge State Analyser Jatin Yadav1,a,Herendra Kumar1, Diksha Garg1, Pragya Bhatt2, C.P. Safvan2 and Jyoti Rajput1,b
1Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India
2Inter-University Accelerator Center, Aruna Asaf Ali Marg, New Delhi 110067, India [email protected]
[email protected] Here we report on the design and implementation of post collision charge state analyser setup. Ar9+ projectile at an energy of 900keV extracted from an electron cyclotron resonance (ECR) ion source was made to interact with Argon gas effusing from a grounded needle positioned perpendicular to the projectile beam. Ar9+ may change its charge state by one ,two, three or more during its interaction with the neutral argon atoms. These charge exchanged projectiles are deflected by a newly installed parallel plate electrostatic analyser (ESA) to check the charge state of the projectile after interaction with argon gas. The recoil ions are extracted by a weak electric field in a time-of-flight mass spectrometer (TOFMS) normal to the projectile and gas jet. The charge exchanged projectiles are detected by microchannel plate(MCP), the output of which is fed into a time-to-digital converter (TDC). The post collision charge state analyser is installed in an experimental chamber which is part of Low Energy Ion Beam Facility (LEIBF) of the Inter-University Accelerator Centre (IUAC), New Delhi. The setup
can be used to study ion-atom and ion-molecule collision experiments. In an ion-atom collision experiment, to measure the time of flight a start trigger is needed. The start trigger can be taken either from an electron ejected during the interaction or from the charge exchanged projectiles. In our previous experiments[1], the start trigger was taken from the electron which is ejected during the reaction. Thus the setup was unable to address the processes where no electron was ejected. The newly designed post collision analyser will be useful for the processes where no electron is ejected. The preliminary testing of the setup has been completed. Different electron captures has been observed from Ar8+ to Ar3+. The deflection for these charged exchanged projectiles are calculated analytically. The experimentally determined values are found to be in good agreement with the analytically calculated values. ________________ [1] Herendra Kumar, Pragya Bhatt, C. P. Safvan and Jyoti Rajput, J. Chem. Phys., 148 064302 (2018)
P-03
Theoretical predictions for ionization cross sections of bio-molecules by high energy proton impact
S. Sammadar1, M. Mondal1, A. Mondal1, 2, K. Purkait1 and M. Purkait1*
1 Dept. of Physics, Ramakrishna Mission Residential College, Narendrapur, Kolkata-700103, West Bengal, India_1
2 Dept. of Physics, Ramsaday College, Amta, Howrah-711401, West Bengal, India_2 *[email protected]
In this work, we reported double differential cross sections (DDCS) for single ionization process induced on bio-molecules by high-energy protons. The calculations are performed within the three Coulomb wave (3CW) approximations [1]. Knowledge of differential and total ionization cross sections is of great interest in many areas such as atmospheric, plasma and biological physics. In particular, an important application of these results is in the area of radiotherapy. The initial wavefuncation of the active electron bound to a particular molecular orbital (MO) is described employing a bio-molecules approximation [2]. The resulting cross sections for any MO is then reduced to a weighted sum of atomic cross sections corresponding to the atomic constituents of the molecules.
Figure: DDCS molecular orbital contributions for the impact of proton on 4CH and 3NH a function of the electron emission angle and for fixed values of the electron emission energy, Solid line represents our results, fill circle presents experimental results [3-4]. ________________ [1] A. Mondal, C. R. Mandal and M. Purkait, J.Phys.B: At.Mol. Opt. Phys. 49, 075201 (2016) [2] J. Pople et al, J. Chem, Phys. 43, 372 (1965). [3] B. Senger, Z. Phys . D: At. Mol. Clusters 9, 79 (1988). [4] M. E. Galassi et al, Phys. Rev. A, 62, 022701 (2000).
P-04
Electrostatic post-collision analyzer to study charge exchange processes
Sumit Srivastav1*, Deepak Sharma1 and Bhas Bapat1 1Indian Institute of Science Education and Research, Homi Bhabha Road, Pune 411008,
India
We are designing an electrostatic cylindrical sector analyzer ( degree deflector) for analyzing ion beams of energy range from 5 keV/q to 30 keV/q. It consists of two concentric cylindrical electrode sectors of same height with radii of R1 = 95 mm and R2 = 110.2 mm, and two aperture plates at entrance and exit of the deflector to reduce fringing of the electric field.
The required potential difference U across cylindrical sector to guide an ion of energy E through a median arc (say radius R0 ) can be calculated by equating electrostatic force and centrifugal force [1]: 𝑚𝑣2
𝑅0 = 𝑞 𝑈
𝑅0ln (𝑅2𝑅1) where is velocity of ion and m is it’s mass
We are planning to perform an experiment, where highly charged projectile interacts with molecular target and there is a possibility of charge exchange process [2], which would result the change in charge state of projectile. So, it becomes important to analyze the charge state of the projectile after collision. We are expecting that the above discussed analyzer would serve our purpose to separate charge state of Ar17+ and Ar18+ with energy up to 30 keV/q.
________________ [1] Kreckel et al, Review of Scientific Instrument 81, 063304 (2010). [2] Luna et al , Phys. Rev. A 93 ,052705 (2016).
P-05
Model Calculation To Study The Orientation Effect In Multiple
Ionisation Of Diatomic Molecule
Deepak Sharma1*, Bhas Bapat1, Pragya Bhatt2 and C P Safvan2 1 Indian Institute of Science Education and Research, Homi Bhabha Road, Pune 411008,
India 2 Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India
Orientation dependence of ionisation cross-section is a long studied process. Theoretical studies – both based on simple geometric argument [1,2] and more elaborate model based on statistical energy deposition (SED) method [3,4] show that a highly charged molecular ion state is more likely to be achieved when the molecule is oriented parallel to the beam direction than when it is oriented perpendicular to the beam direction. The studies of orientation dependence ionisation cross-sections were mainly focused on the N2, O2 and CO molecules, but no attention seems to have been given to the distinction between the homonuclear and heteronuclear nature of the two molecules, and the orientation dependence has been recognised purely as a geometric effect. In our recent article [5], it was shown that heteronuclear nature of CO molecule gives rise to asymmetry in the ionisation cross section and so, orientation effect is not purely a geometric effect but depends on the individual constituents of the molecule. In theoretical calculation of ionisation cross-section, which assume linear trajectory of the projectile, asymmetry in the angular distribution will not emerge, because under the assumption of a linear trajectory the problem is exactly symmetric in the forward and backward hemispheres. Hence it is necessary to take into account the non-linearity of the trajectory in order to explain the asymmetry in the ionisation of a heteronuclear molecule. A simple model is developed to explain the orientation dependence of the multiple ionisation probability. The probability of multiple ionisation is computed for Rutherford-like trajectories with an orientation dependent distance of closest approach. Since the energy deposition as well as the ionisation probability are large for close encounters and small for distant encounters, the value of Dmin (distance of closest approach) should be large for θ = π/2 and small for θ = 0, π. The single ionisation probability is represented by p(b) = p0exp(−b/r), where p0 is the probability at zero impact parameter, r the radius of the removed electron shell, and b is the impact parameter of the collision, different for the two individual atoms of the molecule and dependent on the molecular orientation. For heteronuclear diatomic molecule, the values of p0 and r will be different for both the atoms. Using this model, we are able to predict the asymmetry and anisotropy in the angular distribution of multiple ionisation of heteronuclear molecule CO. This model is further applied to homonuclear diatomic molecules N2 and O2, and predicted values show good agreement with previous results [6]. ________________ [1] K. Wohrer and R. L. Watson, Phys. Rev. A 48, 4784 (1993).. [2] C. Caraby, A. Cassimi, L. Adoui, and J. P. Grandin, Phys. Rev. A 55, 2450 (1997). [3] U. Werner, N. M. Kabachnik, V. N. Kondratyev, and H. O. Lutz, Phys. Rev. Lett. 79, 1662 (1997).
[4] Z. Kaliman, N. Orlić, N. M. Kabachnik, and H. O. Lutz, Phys. Rev. A 65, 012708 (2001). [5] D Sharma, B Bapat, P Bhatt, and C P Safvan, J. Phys. B: At. Mol. Opt. Phys 51, 195202 (2018). [6] B. Siegmann, U. Werner, Z. Kaliman, Z. Roller-Lutz, N. M. Kabachnik, and H. O. Lutz, Phys. Rev. A 66, 0 52701 (2002).
P-06
Kinetic energy release in dissociation of NH3q+ under ion impact
Pragya Bhatt1*, T. Sairam2 and C. P. Safvan1
1Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067 2Tata Institute of Fundamental Research, Hyderabad 500107
Dissociation of molecules under charged particle impact has been an active field of study. The concerted and sequential dissociation of polyatomic molecules is studied by several researchers. We have studied the dissociation of ammonia under energetic highly charged ion impact. The techniques of recoil ion momentum spectrometry and mutli-hit ion detection are used in unison [1] to obtain the kinetic energy release (KER) in the dissociation of NH3
q+ (q=2,3). The experimental data contain a mixed signature (black curve in Figure 1) for the events arising from the dissociation of doubly and triply ionized NH3. We have used the method of dalitz plot [2] to disentangle the events arising from the symmetric concerted dissociation of NH3
3+ from the rest of the events, see Figure 1.
Figure 1. Kinetic energy release distribution for the dissociation of NH3q+ (q=2,3).
The theoretical ab initio calculations using the quantum chemistry package GAMESS are performed to obtain the possible electronic states for the doubly and triply ionized ammonia molecule. The energy values for these states are found to be in reasonable agreement with our experimental results [3]. These calculations further help in identifying the pathway of dissociation of doubly charged NH3 if it dissociates sequentially.
P-06
________________ [1] P. Bhatt, T. Sairam, A. Kumar, H. Kumar, C. P. Safvan Physical Review A 96, 22710 (2017) [2] R. Dalitz, The London, Edinburgh and Dublin Philosophical Magazine Journal of Science 44, 1068 (1953) [3] P. Bhatt et al to be communicated.
P-07
Delayed dissociation of ethylene under ion impact
Pragya Bhatt1, K. Takahashi2, K. Yokokawa2, A. Mizumura2, J. Matsumoto2, H. Kumar3, C. P. Safvan1 and H. Shiromaru2*
1Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067. 2Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397,
Japan. 3Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India.
The dissociation of ethylene is studied under the impact of Arq+ and Xeq+ ions at Tokyo Metropolitan University and Inter University Accelerator Centre, respectively [1-2]. The fragment ions generated in the dissociation of C2H4
2+ are detected using a position sensitive time of flight (TOF) mass spectrometer. The multi ion coincidence technique is used to select ions generated from a particular event with respect to a scattered charged selected projectile or an emitted electron. The observed double ion coincidence TOF maps are shown in figure 1(a-b). The TOF and position information of these ions are used to obtain the survival time of the metastable C2H4
2+ ions assuming that the kinetic energies of these fragments are negligible.
Figure 1. Double ion coincidence map under impact of (a) 1.5 keV/u Ar4+ with Ar3+ as a trigger and (b) 3.4 keV/u Xe9+ with an emitted electron as a trigger.
Our results show that the delayed dissociation of C2H42+ is well described by a
power law decay function rather than a multi component exponential function [3]. This indicates that the vibrational states are statistically populated and that the states with different internal energies contribute to the delayed dissociation of C2H4
2+. This explains why the decay profiles are independent of the method of ionization.
P-07
________________
[1] P J. Matsumoto, H. Tezuka, and H. Shiromaru, J. Phys.: Conf. Ser. 583, 012016 (2015). [2] A. Kumar, J. Rajput, T. Sairam, M. R. Jana, L. Nair, and C. P. Safvan, Int. J. Mass Spectrom. 374, 44 (2014). [3] K. Takahashi et al Phys. Rev. A 98, 062708 (2018).
P-08
Electron Beam Ion Source (EBIS) Facility at IISER, Pune
Deepak Sharma*, Sumit Srivastav, Suddhasattwa Mandal, Arnab Sen and Bhas
Bapat Indian Institute of Science Education and Research, Homi Bhabha Road, Pune 411008, India
Electron Beam Ion Source is a compact ion source for the production of highly charged ions. It is based on the principle of electron impact ionization of neutral atoms [1]. The electron beam emitted from high current cathode is guided through the three drift tubes forming the ions trap (see schematic of EBIS in figure 1). After having passed the drift tubes the electron beam is dumped onto a water cooled electron collector. The electron beam is compressed by an axially symmetric magnetic field formed by two permanent magnets. Due to its negative space charge, the electron beam creates radial trapping for produced ions. The axial trapping of ions is generated by additional potential on the center and third drift tube.
Figure 1. Electron Beam Ion Source Schematic The extraction of the ions is realized by adjusting the voltage on third drift tube. The source can be operated in pulsed mode or leaky mode. For efficient ion extraction the extraction channel includes an electron repeller as well as additional Einzel lens and a quadrupole deflector to improve the shape and quality of the ion beam. Ion beam with diameter of some mm down to sub-mm and with energy of 100 eV/q to 30 keV/q can be extracted from this ion source. Using this ion source and recoil ion momentum spectrometer (RIMS), we intend to study the ion-molecule collision process under non-perturbative regime. ________________ [1] V P Ovsyannikov and G Zschornack, Review of Scientific Instruments 70, 2646 (1999).
P-09
Tuning optical properties of metallic thin film mirrors by low energy
inert gaseous ion beams Krishn Pal Singh, Jayashree Majumdar and Sudeeep Bhattacharjee*
Department of Physics, Indian Institute of Technology-Kanpur, Kanpur 208016, India
The optical properties of metallic thin films (MTF) have attracted large attention of scientific community because of their different behavior as compared to bulk metal. Various practical application in perfect lenses, solar cells, enhanced transmission through holey metal and in mirror coatings for space applications [1, 2] have been realized using metallic thin films. The low energy ions are embedded into the lattice of the host metal and can substantially modify the surface properties of the MTF, such as electrical properties [3], wettability [4] and optical properties. The optical properties of the medium are strongly dependent on the refractive index, which in its turn is related to the dielectric constant [5]. Hence, the optical properties of metallic thin films are expected to be modified upon irradiation with low energy ion beams. We carry out experiments to investigate the above, using a wide range of available ionic species (inert gaseous ions such as Ar, Kr, Xe etc), their energies, fluxes and target MTF. The optical properties of irradiated thin films are investigated by UV-VIS spectroscopy, where we measure the reflection (R) and transmission (T) coefficients. We have investigated the aforementioned optical properties for copper, silver and aluminum MTF irradiated by low energy (0.5 keV) Ar ions with varying fluence. It is found that the wavelength dependence of the reflection, transmission and absorption coefficients change both with ion beam fluence and for different MTF. Metals are generally pure reflectors in the visible and infrared portion of the light. The implantation of foreign impurity in the host metal increases the dielectric media inside it and provides the path for propagation of light through the metal, which therefore decreases the reflection, and increases the transmission and absorption coefficients (A = 1-R-T), with increase in ion beam fluence. In this conference, the optical properties of various type of metallic thin films such as Au, Ag, Al, and Cu irradiated with varying fluence of low energy ion beams of Argon will be presented.
________________ [1] I D Sarcina, M L Grilli, F Menchini, A Piegari, S Scaglione, A Sytchkova and D Zola, Applied optics 53, 314-320 (2014). [2] S Zuccon, E Napolitani, E Tessarolo, P Zuppella, A J Corso, F. Gerlin, M. Nardello and M G Pelizzo, Opt. Mat. Express 5, 176-187 (2014). [3] A Chowdhury and S Bhattacharjee J. Phys. D: Appl. Phys 46, 435304 (2013). [4] S Chatterjee, S Bhattacharjee, S K Maurya, V Srinivasan, K Khare and S Khandekar, EPL 118, 68006 (2017). [5] A N Oraevskii and I E Protsenko Quantum Electronics 31, 252-256 (2001).
P-10
Development of Time-Dependent Schrodinger Equation solver and Its
application to calculate High-order Harmonic Generation by laser-atom interaction
Rambabu Rajpoot1*, Amol R. Holkundkar1, and Jayendra N. Bandyopadhyay1 1Department of Physics, BITS Pilani, Pilani campus, Raj. 333031
We are studying the underlying physical aspects of the higher harmonics generated by the laser-atom interaction, and eventually the generation of the attosecond pulses. The interaction of very intense laser pulse with gas medium results in the generation of high-order harmonics of the fundamental frequency in XUV region. High-order Harmonic Generation (HHG) can qualitatively be explained by the classical model [1]. A tool for the solution of Time-Dependent Schrodinger Equation (TDSE) in 1D has been developed using the Split-Operator method and the results in Ref. [2] has been reproduced for testing purpose and shown in Fig. 1. We have studied the extension of HHG spectra cutoff energy by changing various parameters of the interacting laser pulse. Furthermore, we are planning to extend the TDSE solving tool in two (azimuthal symmetry) and three dimensions.
Figure 1. HHG power spectra in single 5fs and 3fs field as well as in three-color fields.
P-10
-------------------------- [1] P. B. Corkum, Phys. Rev. Lett. 71,1994 (1993). [2] R-F. Lu, H-X. He, Y-H. Guo and K-L Han, J. Phys. B 42,225601 (2009).
P-11
Photoelectron velocity map imaging spectroscopy facility for probing
anion resonances Saroj Barik and G. Aravind*
Department of physics, Indian Institute of Technology Madras, Chennai, India *[email protected]
We have designed and constructed a photoelectron velocity map imaging spectroscopy setup in our lab. A supersonic discharge ion source employed to produce different kind of negative ions. The ions are perpendicularly extracted and mass separated by a linear time of flight mass spectrometer. The desired anion is photodetached in source region of VMI which is achieved by synchronizing the laser with the anion of interest. The photodetached electrons are extracted by VMI electrodes which are detected by a position sensitive detector. From the observed data we can extract the kinetic energy and angular distribution of ejected photoelectrons. The setup is being calibrated using iodine anion produced from methyl iodide (CH3I) as precursor molecule seeded with argon gas. The initial result from the experimental setup will be presented in the conference.
Figure 1. Schematic diagram of photoelectron spectrometer.
P-11
Figure 2.Raw photoelectron image of I- obtained with 355 nm laser
____________
1. Surber, E., Mabbs, R., and Sanov, A., 2003, J. Phys. Chem. A, 107(40), 8215-8224.
P-12
Spin-orbit interaction effect in Wigner-Eisenbud-Smith time delay: a
case study on Xe 3d photoionization Sourav Banerjee1*, Ankur Mandal2, Soumyajit Saha1, and Pranawa C. Deshmukh1, 3
1 Department of Physics, Indian Institute of Technology Madras, Chennai, 600036, India 2 Department of Physics, Indian Institute of Science Education and Research, Tirupati, Tirupati-
517507, India 3 Department of Physics, Indian Institute of Technology Tirupati, Tirupati, 517506, India
Spin-orbit interaction plays a very major role in determining the structure and dynamics of matter [1-3]. In a recent study [4], an effect of interchannel coupling, namely ‘spin-orbit interaction activated interchannel coupling’ (SOIAIC) is elucidated in the weighted averages of WES time delay in photoionization from spin orbit split 4d orbital. Dipole-allowed transition channels contribute to the energy, angle and final-state spin projection dependent time delay in photoionization from the initial state [5]. In [6] we have analysed and pointed out the characteristics of each angle-and-energy resolved spectrum and show the leveraging of SOIAIC in time domain.
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PIPT 90o
ISST 90o
4d3/2,1/2,p
4d3/2
Xe
Fig. 1. Xe WES time delays for 4d3/2,1/2,+ channel.
Present study aims at exploring the SOIAIC in a deep inner shell Xe 3d along with the results as seen in Xe 4d photoionizaiton time delay. Fig. 1 reflects a sample of the works carried out for the present study. WES time delays for 4d3/2,1/2,+ channel is shown in both uncoupled and coupled channel calculations for both 4d3/2 and 4d5/2 subshell photoionizaiton. In near 80eV region we can see the hump like structure which is due to SOIAIC. Variation with respect to angle of emission is very prominent due to the interference of different outgoing channels. A detailed discussion with the help of more results will be elucidated in main presentation. ________________
[1] M. Ya. Amusia et al., Phys. Rev. Lett. 88 093002 (2002). [2] A. Kivimaki et al., Phys. Rev. A 63 012716 (2000). [3] D. A. Keating, P. C. Deshmukh and S. T. Manson, J. Phys. B: At. Mol. Opt. Phys. 50 175001 (2017). [4] A. Mandal S. Saha, and P. C. Deshmukh, Springer Proceedings of ISAMP TC-7 (2018).
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[5] A. Kheifets et al., Phys. Rev. A 94 013423 (2016). [6] “Leveraging of spin-orbit interaction in Wigner-Eisenbud-Smith time delay”, A. Mandal, S. Saha, and P. C. Deshmukh, 13th AISAMP, December 03-08, 2018 , Mumbai, India.
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3rd order nonlinearity based on wavelength mismatching and
quantum interference in microwave driven Y-type atomic system Neeraj Singh* and Ajay Wasan
Department of Physics, Indian Institute of Technology Roorkee, Roorkee – 247667, India
*email: [email protected]
Since the last few decades, controlling the optical properties of atomic medium via coherent fields has attracted the attention of researchers due to its wide application in various areas of optical and atomic physics. This is only possible due to the generation of atomic coherence and quantum interference. The theoretical as well as experimental approaches have been demonstrated that quantum interference leads to enhanced 3rd order Kerr nonlinearity in atomic system [1, 2]. It is well known that atomic optical responses for the probe field are governed by the atom’s velocity, the wavelength and relative propagation of driving laser fields due to Doppler Effect. Thus, the thermal motion of atoms causes the broadening of signals. This broadening can be reduced by properly assuming the propagation direction of laser fields in case of wavelength matched condition. In the real experiment, the wavelength of driving laser fields can be different from each other and this scenario is termed as wavelength mismatching. This wavelength mismatching study has been performed with various kinds of atomic systems in order to see the effect on EIT signals [3]. A theoretical study is carried out for the investigation of first-order linear and third-order nonlinear susceptibility in a microwave driven four-level Y-type atomic system. Based on density matrix formalism, a complete numerical calculation is performed for the case of stationary as well as moving atoms. In this work, we present the wavelength mismatching effect on linear and nonlinear susceptibilities by considering three wavelength regimes, i.e., near matching, partial mismatching and complete mismatching of wavelengths. Thereafter, in case of the near matching regime, the two upper excited states are coupled by a microwave field that makes a closed cycle of transitions. Because of it, a relative phase factor among coherent fields becomes responsible for significant modification of susceptibilities of an atomic medium. An enhanced Kerr nonlinearity with smaller linear probe absorption is obtained under specific parametric condition. Here, we attribute the enhanced Kerr nonlinearity to the quantum interference between transition pathways. In addition, we also present a dressed analysis steady to understand phase-dependent behavior. ________________ [1] H. Hamedi, G. Juzeliunas, Phys. Rev. A 91 (5) 053823 (2015). [2] J. Sheng, X. Yang, H. Wu, M. Xiao, Phys. Rev. A 84 (5) 053820 (2011). [3] A. Urvoy, C. Carr, R. Ritter, C. Adams, K. Weatherill, R. Low, J. Phys. B: At. Mol. Opt. Phys. 46 (24) 245001 (2013).
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Multi Window Ladder Type Electromagnetically Induced Transparency
in 87Rb Atomic Medium at Room Temperature VikasS.Chauhan*,SumitBhushan and Raghavan K. Easwaran*
Department of Physics, Indian Institute of Technology Patna, Bihta,Patna 801003
In this work, multiple windows were observed by using Electromagnetically Induced Transparency(EIT) protocol in 87Rb atomic vapor medium. 5S1/2─5P3/2─5D5/2 transition has been used for the experiment in which 5S1/2─5P3/2 transition is addressed by 780nm weak probe(0.8mW)laser and 5P3/2─5D5/2 transition is addressed by 776nm strong coupling(39mW) laser. We have observed four EIT windows by using above transition as shown in fig1.These multiple EIT [1] windows are capable of storing different frequencies simultaneously hence paving the way for realization of broadband quantum memory(QM). The total band width of the QM is estimated to be 109MHz which is two order of magnitude higher than the QM based on single window EIT [2]. Hence the capacity of the QM memory can be increased.
Fig1.Transmission windows when probe laser scans from 5S1/2─5P3/2 and coupling laser scans from 5P3/2─5D5/2 transition of 87Rb. [1] D. Q. Khoa, N. B. Duc, T. Thanh, H. Q. Quy,C. L. Van, and W. L.Ski , JOSA B 35 ,1536 (2018). [2]L. Ma, O. Slattery and X. Tang, J. Opt. 19 ,043001(2017).
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R-matrix calculations of the photoionization cross sections of Co17+
Mayank Dimria,b*, A. K. Singhb, Man Mohana,b
aDepartment of Physics, Deen Dayal Upadhyaya College, University of Delhi, Delhi-110078,
India bDepartment of Physics & Astrophysics, University of Delhi, Delhi-110007, India.
The total photoionization cross sections of the ground state 2s22p6 (1S0) of Co XVIII ion have been reported using the Close-Coupling Breit-Pauli R-matrix (CC-BPRM) [1] approximation. We have constructed target ion wavefunctions by configuration interaction technique (CIV3) [6]. Our calculated ionization threshold energy for the ground state show better agreement with the NIST [3] ones. To affirm the accuracy and reliability of our CC-BPRM results, photoionization cross section calculations for the ground state have also been performed using the fully relativistic Dirac Atomic R-matrix Code (DARC) [4]. These two independent calculations agree well both in magnitude and resonant photoionization cross sections. The resonance parameters such as resonance positions (Er), widths (Γ) and quantum defects (µ) due to ejection of a 2p or 2s electron from the ground state 2s22p6 (1S0) are also provided by adopting Quigley and Berrington (QB) [5] technique. We believe that the present results should be useful in the modelling and diagnostics of astrophysical plasmas.
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Figure 1. Comparison of present CC-BPRM photoionization cross sections for the ground state 2s22p6 (1S0) of Co XVIII with DARC.
________________ [1] N.S. Scott, K.T. Taylor, Comput. Phys. Commun. 25, 347 (1982). [2] A. Hibbert, Comput. Phys. Commun. 9, 141 (1975). [3] A. Kramida, Yu. Ralchenko, J. Reader, NIST ASD Team, 2018, NIST Atomic Spectra Database (ver. 5.5.6) [Online]. Available at: https://physics.nist.gov/asd. [4] P. H. Norrington. http://www.am.qub.ac.uk/DARC/ 2009. [5] Quigley L, Berrington K, Pelan J. Comput. Phys. Commun. 114, 225 (1998).
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Photoionization of the ground 3s2 (1S0) and excited 3s3p (3Po0,1,2)
states of Se XXIII and atomic data of Se XXIV
Dishu Dawraa*, A. K. Singhb, Man Mohana,b
aDepartment of Physics & Astrophysics, University of Delhi, Delhi-110007, India
bDepartment of Physics, Deen Dayal Upadhyaya College, University of Delhi, Delhi-110078,
India.
The total photoionization cross section calculations of the ground state 2p63s2(1S0) and the first three excited states 2p63s3p (3Po
0,1,2) of Se XXIII ion have been done using the fully relativistic Dirac atomic R-matrix code (DARC) [1]. The target wavefunctions are constructed by performing multiconfiguration Dirac-Fock calculations for the lowest 21 fine structure energy levels belonging to 2p6nl (3 ≤ n ≤ 5) configurations. The calculated target state energies of the core ion Se XXIV show better agreement with the NIST [2] values. To affirm the accuracy and credibility of our DARC results, photoionization cross section calculations of the ground state configuration have also been carried out by employing close-coupling Breit-Pauli R-matrix (CC-BPRM) [3] method. Moreover, we have also reported energy levels and radiative data such as transition wavelengths, radiative rates, oscillator strengths and line strengths for Se XXIV ion using GRASP [4]. Analogous calculations have also been done using FAC [5] and CIV3[7]. The presented results agree well with other experimental and theoretical results available in the literature. We believe that our results should be useful in the modelling and diagnostics of astrophysical and laboratory plasmas.
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Figure 1. Comparison of present DARC photoionization cross sections for the ground state 2p63s2 (1S0) of Se XXIII with CC-BPRM.
____________ [1] P. H. Norrington. http://www.am.qub.ac.uk/DARC/ 2009. [2] A. Kramida, Yu. Ralchenko, J. Reader, NIST ASD Team, 2018, NIST Atomic Spectra Database (ver. 5.5.6) [Online]. Available at: https://physics.nist.gov/asd. [3] N.S. Scott, K.T. Taylor, Comput. Phys. Commun. 25, 347 (1982). [4] I.P. Grant, B.J. McKenzie, P.H. Norrington, D.F. Mayers, N.C. Pyper, Comput. Phys. Commun. 21, 207 (1980). [5] M.F. Gu, Can. J. Phys. 86, 675 (2008). [6] A. Hibbert, Comput. Phys. Commun. 9, 141 (1975).
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Simultaneous control of harmonic yield and energy cutoff of high-order
harmonic generation using seeded plasmonically enhanced fields
Irfana N. Ansari1,*, M. S. Mrudul1, Marcelo F. Ciappina2, Maciej Lewenstein3,4 and Gopal Dixit1,*
1Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
2Institute of Physics of the ASCR, ELI-Beamlines Project, na Slovance 2, 18221 Prague, CzechRepublic
3ICFO – Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Av. Carl Friedrich Gauss 3, 08860 Castelldefels (Barcelona), Spain 4 ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain
*[email protected], [email protected]
We study high-order harmonic generation (HHG) driven by seeded plasmonically enhanced fields. On one hand, plasmonically enhanced fields have shown a great potential to extend the HHG cutoff, an instrumental prerequisite for the generation of attosecond pulses. On another hand, the use of XUV seeds appears to have a considerable potential to improve the HHG conversion efficiency, which is typically modest when a unique fundamental laser pulse is employed. By mixing these two sources, we show that it is possible to simultaneously boost the HHG cutoff and to increase the harmonic photon flux [1]. Also, the intensity of the harmonics are found to be decreasing gradually with a built-in oscillation. The time-frequency map and population dynamics of electronic states are used to understand the underlying mechanism of the generated spectra. The interplay of the population dynamics and the interference of short and long trajectories explains the oscillatory behavior in the yield of HHG. Moreover, for higher strengths of spatial inhomogeneity, the harmonics are emitted in a short span of time and the emission times are well separated. The combination of these features potentially enables one to generate intense and spectrally broad attosecond pulse trains.
________________ [1] I. N. Ansari, M. S. Mrudul, M. F. Ciappina, M. Lewenstein, and G. Dixit, Phys. Rev. A 98, 063406 (2018).
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Real-Space Recollision Picture in High-Harmonic Generation from Solids
Mrudul M. S.1, Adhip Pattanayak1, Misha Ivanov2,3,4 and Gopal Dixit1* 1Department of Physics, IIT Bombay, Powai, Mumbai 400076
2Max-Born Institut, Max-Born Straße 2A, 12489 Berlin, Germany 3Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom
4Department of Physics, Humboldt University, Newtonstraße 15, 12489 Berlin, Germany *[email protected]
High harmonic generation (HHG) in gases is understood in terms of the popular three-step model. It is also well established from this real-space picture that electron recollision with the parent ion guides our understanding of the highly nonlinear response of atoms and molecules to intense low-frequency laser fields. Recently, HHG was experimentally realised from solids. Due to the periodicity of the solids, the mechanism of HHG can be explained using the band-structure picture in the momentum space [1]. In this picture, recombination of the conduction band electron with the valence band hole leads to the higher order harmonics. This mechanism was found to be useful for the band-structure reconstruction. In this work, we use numerical simulations to directly test and confirm the real-space recollision picture as the key mechanism of HHG in solids. Our tests take advantage of the well-known characteristic features in the molecular harmonic spectra [2], associated with the real-space structure of the molecular ion. We show the emergence of analogous spectral features when similar real-space structures are present in the periodic potential of the solid- state lattice. This work demonstrates the capability of HHG imaging of spatial structures of a unit cell in solids. ________________ [1] G. Vampa, T. J. Hammond, N. Thiré, B. E. Schmidt, F. Légaré, C. R. McDonald, T. Brabec, D. D. Klug, and P. B. Corkum, Physical review letters, 115(19), 193603 (2015). [2] M. Lein, N. Hay, R. Velotta, J. P. Marangos, and P. L. Knight, Physical Review A 66, 023805 (2002).
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Effects of Vacancy In Solid High Harmonic Generation
Adhip Pattanayak1, Mrudul M.S.1, and Gopal Dixit1
Department of Physics, IIT Bombay, Powai, Mumbai 400076, India
Solids yield more efficient high harmonic generation (HHG) due to its periodicity and high electron density in comparison to the gaseous systems. We investigated the role of defects (vacancy) in solid and the corresponding HHG. As the concentration of vacancy is increased, the spectrum profile of the harmonic yield gradually turns into a single slanted spectrum without having an abrupt drop between two plateaus. This behavior of the harmonic profile is illustrated by the splitting of degenerate bands. The appearance of these degenerate bands in the effective band structure is due to the breaking of translational symmetry in real space. As a consequence, new energy states become visible near the Fermi level. These newly originated energy states open more channels for transitions and contribute remarkably to the total current density and hence, the HHG.
________________
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Ion Trapping results of High Intensity Laser Ion Trap Experiment
(HILITE) at GSI, Germany Sugam Kumar1*, S. Ringleb 2, N. Stallkamp2,3, M. Vogel2, W. Quint3,4, Th. Stohlker2,3,5
and C.P. Safvan1. 1 Inter University Accelerator Centre, New Delhi, India
2 Institute of Optics and Quantum Electronics, Friedrich-Schiller-Universitat, Jena, Germany 3 GSI Helmholtzzentrum for Schwerionenforschung GmbH, Darmstadt, Germany
4 Physikalisches Institut, Ruprecht Karls-Universitat, Heidelberg, Germany 5 Helmholtz-Institut Jena, Germany
We present the initial results of Ions trapping and measurements with non-destructive detection system in the framework of High Intensity Laser Ion Trap Experimental (HILITE), currently operated at GSI, Germany, which allows the localisation, cooling and positioning of a well-defined ion target. It consists of an open-endcap Penning trap placed in the centre of a 6T superconducting magnet and cooled down to liquid helium temperature. This Penning trap is transportable and designed to be connected to different laser systems. The trap is equipped with an electron-beam ion source (EBIT) which delivers highly charged ions for storage in the trap. Experimental setup consisting of: EBIT ion source, Wien filter, beam dump, main chamber and magnet with trap. The setup has an overall length of about 3 meters, can be split up into three parts and is transportable. We intend to prepare and use a well-defined single-species ion cloud inside the Penning trap. We plan to measure directly the two-photon absorption or three-photon absorption as a function of the photon energy.
Figure 1. Schematic cut-out of the Penning trap with the ion target stored in the centre and laser light entering from the right.
In view of the simple system to be used and the clear experimental conditions, our results can be used for a benchmarking of the theory of non-linear interactions in X-
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ray regime as well as to push further the non-linear spectroscopy at X-ray wavelengths. ________________ [1] M. Vogel, W. Quint, G.G.Paulus, Th. Stöhlker, NIMA 285, 65-71 (2012). [2] S. Ringleb, M. Vogel, S. Kumar, W. Quint, Journal of Physics Conference Series 635, 092124 (2015).
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Study of Electromagnetic Induced absorption in degenerate two level
system I.H. Subba, R.Kumar, N.Sharma and A.Tripathi
1 Department of Physics, School of Physical Sciences, Sikkim University, Gangtok, Sikkim *[email protected]
We have investigated the Electromagnetic Induced Absorption (EIA) in degenerate two level system (DTLS) of Rb87 D2 line by involving F=2 and F’=3 states using pump probe spectroscopy in presence of external transverse magnetic field. Two cases i.e, pump beam polarization parallel and perpendiculars with respect to the orientation of applied magnetic field are studied (probe beam polarization is perpendicular to probe beam). We experimental demonstrated the observation of two well-resolved N-type system at higher magnetic field for parallel polarization, which was found to be absent in case of perpendicular polarization. This is been attributed to the population realignment in the presence of magnetic field. This is first experimental observation of the theory proposed by Zigdon et.al.1 wherein it was shown that in presence of magnetic field EIA can be observed in DTLS system because of the transfer of coherence (TOC) between Zeeman sublevels. The maximum contribution to form EIA would be from outermost Zeeman sublevels because of the presence of closed transition and hence efficient transfer of coherence. In this talk the obtained result and the extension of the work would be discussed.
.
Figure 1. EIA in DTLS for different values of applied magnetic field
________________
[1] T Zigdon, AD Wilson-Gordon, and H Friedmann. Physical Review A, 77(3):033836, 2008.
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Role of Helium Nanodroplet Environment on the Ionization Dynamics
of Acetylene Under EUV Synchrotron Radiation
Suddhasattwa Mandal1*, Ram Gopal2, Robert Richter3, Marcello Coreno3, Marcel Mudrich4, Alessandro D’Elia5, Mykola Shcherbinin4, Hemkumar Srinivas6, Bhas Bapat1,
Sivarama Krishnan7 and Vandana Sharma8
1 Indian Institute of Science Education and Research Pune, Pune – 411008, Maharashtra, India 2 TIFR Centre for Interdisciplinary Sciences, Hyderabad – 500107, Telangana, India
3 Elettra-Sincrotrone Trieste, Strada Statale 14-km 163.5, 34149 Basovizza, Trieste, Italy 4 Aarhus University, 8000 Aarhus C, Denmark
5 University of Trieste, Department of Physics, 34127 Trieste, Italy 6 Max-Plank-Institut für Kernphysik, 69117 Heidelberg, Germany
7 Indian Institute of Technology Madras, Chennai – 600036, Tamil Nadu, India 8 Indian Institute of Technology Hyderabad, Sangareddy – 502285, Telangana, India
Helium nanodroplet, a weakly-bound van der Waals cluster, provides a unique opportunity to investigate inter atomic and molecular processes, where transfer of excitation or ionization from the helium environment to the embedded dopant species plays an important role in the ionization dynamics of the dopant [1-3]. We have studied the role of the host He nanodroplet excitation and ionization on the ionization processes of acetylene by EUV synchrotron radiation in the photon energy range of 20eV to 26eV, by detecting the photoelectrons in coincidence with the photoions with a velocity map imaging spectrometer and a time of flight mass spectrometer respectively [4]. The photoion yields of C2H2
+ ions at this energy range, shown in Fig.1, indicate that the ionization process in acetylene is highly influenced by the presence of the host helium matrix. We observe two ionization peaks of the doped acetylene
Figure 1. Comparison of C2H2+ photoion yields from C2H2 doped He nanodroplet
ionization and from gasphase C2H2 ionization at different photon energies from 20eV to 26 eV
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at 21.6eV and 23.9eV, below the atomic helium ionization threshold (24.6eV). We would like discuss the ionization mechanisms of C2H2 at these two photon energies and at energy above 24.6eV, by presenting the photoion mass spectra and the coincidence photoelectron spectra. ________________ [1] D. Buchta, S. R. Krishnan et al.: J. Phys. Chem. A, 117, 4394 (2013) [2] A. C. Laforge et al.: Phys. Rev. Lett., 116, 203001 (2016) [3] M. Shcherbinin, A. C. LaForge, M. Hanif, R. Richter and M. Mudrich: J. Phys Chem. A, 122, 1855 (2018) [4] P. O’Keeffe et al.: Review of Scientific Instruments, 82, 033109 (2011)
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Supercontinuum generation in Argon through hollow core fiber for use in atomic and molecular physics experiments
Pritha Dey1, C. Vijayan1 and Sivarama Krishnan1* 1 IIT Madras
Supercontinuum generation (SCG) is the generation of a broadband white light source having the coherent property of a laser by propagating intense optical pulses through a strongly nonlinear optical media causing the pulses to get broadened in frequency domain [1]. These broad spectral pulses are used to generate coherent attosecond pulses wich is high-harmonic generation (HHG). HHG is used in molecular-orbital tomography, where the goal is to reconstruct the molecular orbital using the HHG-spectrum [3]. SCG in bulk medium cause damage to the medium and the beam profile becomes poor due to multiphoton ionization. Therefore SCG in high energy pulses use the technique of self-phase modulation of a noble gas under pressure inside a hollow cylindrical fused silica fiber (HCF) [2].
Figure 1. Spectral broadening in Ar gas as a function of input pulse width at 5 bar pressure.
Since the nonlinear effects resulting to the SC are highly dependent on the dispersion of the medium, modifying the dispersion properties wisely can reduce the high-power requirements for SCG. Here we have studied the modification of the SC spectra as a function of the Argon gas pressure and the input pulse width. The gas pressure causes the dispersion property of the medium to change causing a change in the nonlinear optical process involved in SCG. On the other hand the nonlinear kerr effect is dependent on the peak intensity (I0) of the pulse and I0 is inversely
proportional to pulse width. So, these two factors govern the spectral broadening to a great extent.
________________
[1] Alfano, R. R., & Shapiro, S. L. (1970, 03). Emission in the Region 4000 to 7000 Å Via Four-Photon Coupling in Glass. Physical Review Letters, 24(11), 584-587. doi:10.1103/physrevlett.24.584 [2] Nisoli, M., Silvestri, S. D., & Svelto, O. (1996, 05). Generation of high energy 10 fs pulses by a new pulse compression technique. Applied Physics Letters, 68(20), 2793-2795. doi:10.1063/1.116609 [3] J. Itatani, J. Levesque, D. Zeidler, Hiromichi Niikura, H. Pépin, J. C. Kieffer, P. B. Corkum & D. M. Villeneuve. (2004) Nature, 432(7019):867-71. doi:10.1038/nature03183
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Doppler-free spectroscopy of thermal Rubidium atoms for laser
frequency stabilization
Rajni Bala, Omshankar, Ingo Nosske, Vivek Venkataraman and Joyee Ghosh*
Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
Quantum coherent phenomena in atomic systems such as EIT are of great interest due to potential applications in magnetometry, quantum memories, precision spectroscopy, ultralow power nonlinear optics and atomic clocks [1]. Thermal gases of alkali atoms inside transparent glass vapor cells provide a suitable platform to explore these near-resonant light-matter interactions at room temperature. Extremely narrow-linewidth (sub-kHz) features have been obtained in such Doppler-broadened media by carefully eliminating various decoherence mechanisms. We aim to investigate related quantum nonlinear optical processes using a temperature-controlled quartz vapor cell containing thermal Rubidium (Rb) atoms in our laboratory. Here we report on the realization of Doppler-free spectroscopy on the Rb D2 line (~780 nm) using two methods, viz. saturated absorption spectroscopy (Fig. 1(a)) and polarization spectroscopy (Fig. 1(b)). The narrow lineshape features in quantum coherent interactions like EIT can be broadened by laser frequency drifts during the measurement time due to unwanted fluctuations in the laser temperature, current etc. Hence, laser frequency stabilization becomes very important in such studies requiring precision spectroscopy. We have built an optical setup of polarization spectroscopy to directly measure the error signal that can be used as feedback to the voltage of the piezo-electric stage of ~780nm probe ECDL (external cavity diode laser).
Figure 1. (a) Doppler-free transmission spectrum measured by saturated-absorption spectroscopy.
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The Doppler-broadened background absorption is in excellent agreement with the theoretically calculated transmission spectrum for the Rb D2 line [2]. (b) Direct error signal (which can be used for laser locking) obtained from the balanced photodiode via polarization spectroscopy for the Rb D2 line [3].
The magnitude of this error signal measured can be further enhanced by increasing the power of the pump beam and/or by eliminating stray (e.g. the earth’s) magnetic fields using mu-metal sheets. ________________ [1] M. Fleischhauer, A. Imamoglu, J. P. Marangos, Rev. Mod. Phys. 77, 633 (2005). [2] P. Siddons, C. S. Adams, C. Ge, I. G. Hughes, J. Phys. B: At., Mol. Opt. Phys. 41, 15504 (2008). [3] C. P. Pearman, C. S. Adams, S. G. Cox, P. F. Griffin, D. A. Smith, I. G. Hughes, J. Phys. B: At. Mol. Opt. Phys. 35, 5141 (2002).
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Electron impact cross section study of Furfural A.Chaudhari1*, H.Bhutadia1, C. Limbachiya2 and M. Vinodkumar3
1 Government Engineering College, Patan,Gujarat,384265,India 2Department of Applied Physics, The M. S. University Baroda, Vadodara-390001, India
3V P & R P T P Science College, Vallabh Vidyanagar-388 120, India *[email protected]
We initially became interested in furfural (C5H4O2) due to its importance in many industries1 and, in particular, due to its possible production through atmospheric-plasma treatments of biomass[1,2]. In any likely application of the latter, for example, through the commercial establishment of a bio-refinery, the plasma action will need to be understood through some form of modelling or simulation, with electron scattering cross sections for all relevant species in the plasma being just one of the required inputs. It is hoped that fundamental scattering data of key biomass subunits, and theirinclusion in plasma models, can provide insights into the mechanisms of those plasma actions with different forms of biomass that are built from varying fractions of complex polymers(cellulose, hemicellulose, and lignin). As a consequence, we have undertaken a electron impact cross sectional study of furfural. A comprehensive theoretical study is carried out for electron interactions with furfural (C5H4O2) over a wide range of electron impact energies. We compute total ionization cross sections (TICS) and total cross sections (TCS) using the spherical complex optical potential (SCOP) method [3] for high energy calculations (15 eV to 5000 eV). We make comparison of our calculated data with experimental data of Jones et al [4]. Detailed results will be presented at the time of Conference.
Figure 1. Schematic diagram of furfural (C5H4O2). ________________ [1] J. Amorim, C. Oliveira, J. A. Souza-Correa, M. A. Ridenti, Plasma Processes Polym. 10, 670 (2013). [2] N. Schultz-Jensen, F. Leipold, H. Bindslev, A. Thomsen, Appl. Biochem. Biotechnol. 163, 558 (2011).
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[3] H. Bhutadia, A.Chaudhari, M.Vinodkumar, Molecular Physics, 113, 3654–3662 (2015). [4] D. B. Jones, R. F. da Costa, M. T. do N. Varella, M. H. F. Bettega, M. A. P. Lima, F. Blanco, G. García, M. J. Brunger, The Journal of Chemical Physics, 144, 144303 (2016).
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Cross sectional study of pyridazine molecule on electron impact H.Bhutadia1*, A.Chaudhari1, M.Vinodkumar2 and C.Limbachiya3
1 Government Engineering College, Patan,Gujarat,384265,India 2V P & R P T P Science College, Vallabh Vidyanagar-388 120, India
3Department of Applied Physics, The M. S. University Baroda, Vadodara-390001, India *[email protected]
We investigated electron impact ionization and total cross section of pyridazine, C4H4N2, molecules by SCOP method[1] in the energy range from the ionization threshold up to 5000 eV theoretically. Pyridazine (1,2-diazine) is acyclic isomer of pyrimidine, but now the two nitrogen atoms of the molecule are adjacent to each other in the ring at positions (1) and (2). Figure 1 shows one of the two canonic forms of the resonance hybrid of pyridazine, which has single N(1)-N(2) and double C(4)=C(5) bonds and has a greater contribution into the structure of the pyridazine molecules [2]. The aims of this work were to provide data for comparison with the corresponding results for pyrimidine ionization and to draw attention to similarities and differences in the cationic fragmentation of both molecules. Thus, we expect that the differing nitrogen atom positions in the two molecular rings will cause differences in the efficiencies of the fragmentation channels. We make comparison of our calculated data with experimental data of Dampc et al [3]. Detailed results will be presented at the time of Conference.
Figure 1. Schematic diagram of pyridazine (C4H4N2).
________________ [1] M.Vinodkumar, H.Desai, P. C. Vinodkumar, RSC Adv., 5, 24564–24574(2015). [2] A.R. Berces, P.G. Szalay, I. Magdo, G. Fogarasi, G. Pongor, J. Phys. Chem. 97, 1356 (1993). [3] M. Dampc, P.Mozejko, M. Zubek, Eur. Phys. J. D 72, 216 (2018).
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Low energy electron interactions with Iodine molecule (I2)
Hitesh Yadav1,2*, Minaxi Vinodkumar2 and P. C. Vinodkumar1
1 Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Gujarat, India 2 V. P. & R. P. T. P. Science College, Vallabh Vidyanagar, Gujarat, India
A theoretical study is carried out for electron interactions with Iodine molecule (I2) for incident energies ranging from 0.1 eV to 20 eV. The computations are carried out using Quantemol- N, a computational code, utilizing the UK molecular R-matrix code. Electron interactions with I2 molecule was tested with several target models in its equilibrium geometry and the results are presented for the best model. Scattering calculations were performed to yield resonance parameters along with Dissociative electron attachment cross sections (DEA). Apart from this, the study also focused on calculations of various cross sections such as elastic, electronic excitation, differential, momentum transfer, ionization and total cross sections. The elastic, electronic excitation, differential, momentum transfer and total cross sections are presented for the first time for electron interaction with iodine molecule to the best of our knowledge.
Dr. Minaxi Vinodkumar acknowledges DST-SERB, New Delhi for Major research project [EMR/2016/000470] for financial support under which part of this work is carried out. ________________
[1] J. Tennyson, Phys. Rep., 491, 29-76 (2010). [2] H. Yadav, M. Vinodkumar, C. Limbachiya and P. C. Vinodkumar, J. Phys. B: 51, 045201
(2018). [3] H. Yadav, M. Vinodkumar, C. Limbachiya and P. C. Vinodkumar,, Molecular Physics, 115,
952 (2017).
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Electron capture cross sections from biological molecules by bare projectile impact
A. Mondal1, 2, K. Purkait1, S. Samaddar1, S. Halder1 and M. Purkait1*
1 Dept. of Physics, Ramsaday College, Amta, Howrah-711401, West Bengal, India_1 2 Dept. of Physics, Ramakrishna Mission Residential College, Narendrapur, Kolkata-700103,
West Bengal, India_2 *[email protected]
Electron capture from atoms and molecules by charged particle impact are of relevance in many areas like astrophysics, plasma physics, and radiobiology. In particular, in medical physics they are the main mechanisms leading to energy loss for swift ions in the living matter at medium and high impact energies. Previous calculations of total cross sections (TCS) for water and DNA molecules were done using the CDW-EIS approximation [1-2]. In this work we present the TCS for single electron capture from biological molecules by bare ion impact in the framework BCCIS approximation. Two different approximations have been considered for molecular targets. Bragg’s aditivity rule and molecular representations of the bound state target wave functions. In the latter, the cross section is approximated by linear combinations of atomic cross sections. The TCS for electron capture can be written as
∑ ∑∑= =
==N
j
N
j
N
iat,ij,ijmol
j
σξσσ1 1
,
Where Nj is the total number of atomic components of the j-MO and iat ,σ refers to the corresponding atomic orbital cross sections indicated in the LCAO descriptions.
Figure: Total cross sections for He2+-H2O collisions as a function of projectile energy. Theory: solid curve, present DW results. Expt.: solid upper triangle, results of Rudd et al [3]. ________________ [1] C. Champion et al, Phys. Med. Biol. 57, 3039 (2012). [2] M. A. Quinto et al, Eur Phys. J. B 71, 35 (2017). [3] M. E. Rudd et al, Phys. Rev. A 32, 2128 (1985).
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Probing Functional Group Dependence in Dissociative Electron Attachment Using Negative Ion Momentum Imaging
Samata Gokhale1,2, Krishnendu Gope1, 3, Vishvesh Tadsare1, Matthew Bain4, Michael N R Ashfold4, E Krishnakumar1, 5 and Vaibhav S Prabhudesai1 *
1Tata Institute of Fundamental Research, Mumbai, India, 400005
2University of Mumbai, Mumbai, India, 400098
3The Hebrew University of Jerusalem, Israel, 9190401 4University of Bristol, Bristol, United Kingdom, BS8 1TS
5Raman Research Institute, Bangalore, Karnataka, India, 560080
Dissociative electron attachment (DEA) is the most efficient way to explore the structure and dynamics of excited states of molecular negative ions. More importantly, DEA has been shown to be a tool for chemical control [1-3]. It has been shown that H- formation from DEA to aliphatic compounds follows a pattern that depends on the functional group present and roughly mimics that shown by the prototype hydride - e.g. H- from DEA to alcohols and amines show parallels with that from DEA to water and ammonia, respectively [3]. This functional group dependence of DEA process leads to site selective fragmentation of N-H, C- H and O-H bonds using electron energy as a control parameter. Beyond 4eV of electron energy, this site selectivity has been found to stem from core excited resonances. In the case of N-H and O-H bonds, the localization of excitation is understood to be due to lone pair excitation of N or O atom.
In aromatic organic compounds like aniline, benzyl amine, pyrrole, etc., delocalized electrons influence this site selectivity due to mixing of lone pair electrons. In pyridine, where lone pair electrons of N do not become part of delocalized pi electron cloud, H- from C-H site shows exactly same DEA behaviour as that from benzene [4]. On the other hand, in aniline, H- from its N-H site shows deviation in DEA dynamics as compared to that from ammonia because of influence lone pair electrons. Whereas in benzyl amine, as lone pair electrons are shifting away from delocalized pi electron cloud, H- from N-H site shows similar DEA behaviour as that from ammonia [5] at same electron energy. Pyrrole is a five membered heteroatomic aromatic compound in which lone pair electrons of N become part of delocalized pi electron cloud. H- from its N-H site shows similar angular distribution as that from aniline. H- from its C-H site shows intriguing dynamics unlike that from benzene. We believe that this
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distinguishing feature might be a signature of mixing of lone pair electrons with delocalized pi electron cloud. We also compare pyrrole results with N-methyl pyrrole under similar conditions.
[1] V. S. Prabhudesai, V. Tadsare, S. Ghosh, K. Gope, D. Davis, E. Krishnakumar, J. Chem. Phys. 141, 164320 (2014). [2] V. S. Prabhudesai, A. H. Kelkar, D. Nandi, E. Krishnakumar, Phys. Rev. Lett. 95, 143202 (2005 [3] E. Krishnakumar, V. S. Prabhudesai, N. J. Mason, Nat. Phys. 14, 149 (2018).
[4] V. Tadsare, Ph. D. Thesis, Tata Institute of Fundamental Research, (2018). [5] N. B. Ram, E. Krishnakumar, J. Chem. Phys.136, 164308 (2012).
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Absolute double differential cross section of bremsstrahlung radiation produced in collisions of 3.5 keV electrons with free SF6
molecule.
Prajapati1, B. Singh1, B.K. Singh1 and R. Shanker1* 1Atomic Physics Laboratory, Department of Physics, Institute of Science, Banaras Hindu
University,Varanasi-221005
In collisions of energetic charged particles, for example, electrons or ions with atoms/molecules, the collision events undergo two most important processes, namely, the emission of characteristic x-rays and of non-characteristic radiation or bremsstrahlung (BS). There was a growing interest experimentally and theoretically in determination of BS cross sections due to their importance in different areas of science and technology. Information concerning the angular dependence of the BS radiation produced from electron-atom/molecule collisions is much limited [1-2]. This type of studies has many applications in di fferent areas of example, radiation physics, nuclear physics, radiation therapy, astrophysics, plasma and fusion physics and in biological exposures. In view of this we present a new measurement on spectral and angular dependence of absolute double differential cross sections (DDCS) of bremsstrahlung (BS) radiation produced by 3.5 keV electrons in scattering with a free SF6 molecule by using a Si-PIN photodiode detector in the angular detection range of 450-1100 relative to the direction of incident electrons. Angular distributions of the BS photons are found to be anisotropic. The experimental DDCS spectra are compared with the theoretical calculations obtained from atomic-field BS formulations of Kissel-Quarles-Pratt (KQP) [3] using the ‘additivity hypothesis’. A fair agreement is observed between the measured results and those obtained from KQP calculations for both the energy and the angular spectral distributions of BS radiation. The anisotropy of dipole radiation defined by a polarization parameter P (or degree of polarization) was also measured as a function of photon energy. The detailed results will be presented in the conference.
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Figure 1. Absolute DDCS of BS photons produced in the energy range of 2.0 – 3.4 keV by 3.5 keV electrons in scattering with a free SF6 molecule detected at angle 900 with respect to the
electron beam direction.
______________ [1] M. Aydinol, R. Hippler, I. McGregor, and H. Kleinpoppen, J. Phys. B At. Mol. Phys. 13, 989 (1980). [2] S. Prajapati, B. Singh, B. K. Singh, and R. Shanker, Radiat. Phys. Chem. 153, 92 (2018). [3] L. Kissel, C. A. Quarles, and R. H. Pratt, At. Data Nucl. Data Tables 28, 381 (1983).
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Electron impact excitation of highly charged Ge-like xenon ion Swati Bharti*, Lalita Sharma and Rajesh Srivastava
Indian Institute of Technology Roorkee, Roorkee Uttarakhand 247667
Highly charged ions (HCI) have emerging applications in various field of science and technologies such as plasma physics to diagnose and model the plasma properties for fusion devices [1, 2]. The extreme ultraviolet (EUV) radiation emitted by the highly charged ions carry information about plasma parameters and impurities in plasmas. Also, EUV radiation is expected to be important in the development of the next generation lithography, which is extremely useful for evolution of semiconductor devices. Since in plasma, electron impact excitation of ions is one of the dominant processes which excite the ions and on subsequent decay emit radiations which are the prime input for plasma diagnostics. The experimental electron cross section data for HCI is very limited therefore, role of reliable theoretical methods for electron excitation is very crucial.
In the present work, we have considered electron excitation collisions with highly charged Ge-like xenon ion Xe22+. Such a study is challenging as Xe22+, being open-shell and heavy ion, has many fine-structure levels with appreciable splitting. This ion can be used in the International thermonuclear Experimental Reactor (ITER) for cooling the edge plasma. There are no previous theoretical or experimental studies for the electron impact excitation of the Xe22+ ion. The earlier studies on this ion have only reported the energy levels and their energies as well as transition rates [3, 4]. We have considered the electron induced 4s24p2→ 4s4p3 and 4s24p2→4s24p4d fine-structure transitions in Ge-like xenon ions in the incident electron energy range from 10 to 100 eV [5]. In order to obtain the cross sections, the bound state wavefunctions are obtained within the multi-configuration Dirac-Fock approach. Since the accuracy of the atomic wavefunctions determines the validity of the cross sections, we have compared our calculated excitation energies and oscillator strengths for the above fine-structure transitions with the available other theoretical results [3, 4]. Analytic fitting of the calculated cross sections data are also done to provide cross-sections at any desired energy for plasma applications. The details of the theoretical method and the obtained cross section results will be presented at the conference. [1] J. D. Gilaspy, J. Phys. B: At. Mol. Opt. Phys., 34, R93 (2001). [2] D. A. Liedahl, Spectroscopic Challenges of Photoionized Plasmas, Eds. G. Ferland, D. W. Savin, San Francisco, ASP Conference Series, p. 417 (2001). [3] O. N agy and F. E l-Sayed, At. Data Nucl. Data Tables, 98, 373–390 (2012). [4] L. H. Hao, X. P. Kang and J. J. Liu, Journal of Applied Spectroscopy, 84, 337, (2017). [5] M. F. Gu The flexible atomic code Can. J. Phys. 86 675–89, (2008)
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Excitation of HO2 by electron impact P. Modak#, A. Singh, S. Singh, H. Tomer and B. Antony*
Indian Institute of Technology (Indian School of Mines) Dhanbad
#[email protected]; *[email protected]
The present study aim to focus on the excitations of HO2 by electron impact. It is an open shell target, having relevance in the study of atmospheric sciences [1], marine chemistry [2] and cell biology [3]. This species play key role in photolysis of Cl2SO [4]. The present target has many excited states and many of them are metastable. Thus electron induced excitation of HO2 can lead to the understanding of the physiochemical processes in such environments. The present calculations are performed using UK R-matrix formalism [5]. For the simplicity of calculation, a sphere of radius 10 au is chosen to enclose the entire charge density of the target. Thus, depending upon different short and large range interaction potential, the whole configuration space is divided into two parts; inner region and outer region. The R-matrix basically provides a bridge between these two regions at the surface of R-matrix sphere. All the calculations are performed using cc-pVDZ basis set in the ground state geometry of HO2. The dipole moment of HO2 is very high, hence large number of excited states are considered for convergence of target wave function. The calculated value of dipole moment in the present work is 2.09 D, which matches exactly with that obtained from the microwave spectrum of HO2. Hence, the present target model employed in the present work gives a fair description of this radical. The results are obtained in terms of cross section from different excitation channels and many of them support long life.
Figure 1. Division of configuration space in R-matrix calculation. ________________ [1] D. Stone, L. K Whalley and D. E Heard, Chem. Soc. Rev. 41, 6348 (2012). [2] L. K. Whalley, K. L. Furneaux, A. Goddard et al, Atmos. Chem. Phys. 10 1555 (2010). [3] A. De. Grey DNA and Cell Biology 21 252 (2002). [4] M. Szori, I. G. Csizmadia, C. Fittschen and B. Viskolcz, J. Phys. Chem. A 113 9981 (2009). [5] J. Tennyson, Phys. Rep. 491, 29-76 (2010).
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H- Production from H2 by dissociative electron attachment and dipolar dissociation in the energy range 0.5eV to 100eV
Suvasis Swain1, E. Krishnakumar2 and Vaibhav S. Prabhudesai1*
1 Tata Institute of Fundamental Research, Mumbai, India 400005 2Raman Research Institute, Bengaluru, India 560080
Electron collision with H2 is the simplest system in the context of several scattering related phenomena. Low energy electron collision with H2 that results in dissociative electron attachment (DEA) has shown the generation of quantum coherence among negative ion resonances. This has been found to result in the interference of two quantum paths showing asymmetry in angular distribution of the fragment anion (H-) [1]. On the other hand, the dipolar dissociation (DD) which is active beyond 17 eV of electron energy, results from the excited neutral states that dissociate to H- and H+ fragments. These states have been shown to behave like heavy Rydberg states of the system where the H- is bound to the proton just like single electron is attached to a proton in H atom [2]. Apart from the importance of these phenomena in various applications that range from plasma processing to astrochemistry, this particular system is the ideal one to understand these features from fundamental physics point of view. Here, we present an experimental study of H- formation from H2 by DEA as well as by DD process over the energy range 0.5 to 100 eV. The processes are studied in terms of absolute cross section and momentum distribution of the H- ions formed from the electron collision. We use relative flow technique [3] to measure the absolute cross section and velocity slice imaging technique [4] to measure the momentum distribution of the anion produced. As reported earlier [5], in the 0.5 to 17 eV range, DEA results in the H- production, seen in the form of three peaks in the ion yield curve. The measured cross sections are also found to be consistent with the earlier reported values. In the energy range beyond 17 eV, DD is the primary process of H- production and the absolute cross section for this process in an extended energy range is measured for the first time. The earlier measurements have also reported an isotope effect in both DEA as well as in DD near threshold energy.
________________ [1] E. Krishnakumar, V. S. Prabhudesai and N. J. Mason, Nat. Phys. 14, 149 (2018). [2] M. O. Vieitez, T. I. Ivanov, E. Reinhold, C. A. de Lange, and W. Ubachs, Phys. Rev. Lett. 101, 163001 (2008). [3] S. K. Srivastava, A. Chutjian, and S. Trajmar, J. Chem. Phys. 63, 2659 (1975). [4] K. Gope, V. Tadsare, V. S. Prabhudesai and E. Krishnakumar, Euro. Phys. J. D 71, 323 (2017). [5] E. Krishnakumar, S. Denfl, I. Cadez, S. Markelj and N. J. Mason, Phys. Rev. Lett. 106, 243201 (2011).
P-34
Study of Electron Excitation and polarization of Tungsten Ions
Neelam Shukla, Priti, Lalita Sharma, and Rajesh Srivastava*
Indian Institute of Technology Roorkee (IITR), Roorkee, India-247667
Tungsten and its ions are attracting a lot of attention of researchers because of its involvement as a plasma facing component in various magnetic fusion devices, e.g., it is planned to be used in the divertor region of the International Thermonuclear Experimental Reactor (ITER) [1]. The reason is its extraordinary physical and chemical properties such as high tensile strength, melting point and low erosion characteristics. The ITER plasma will have a very high temperature range and is sufficient to ionize tungsten which is present in the divertor region up to its different ionic states. Thus, there will be several charged state of tungsten ions present in ITER plasma. Therefore, for diagnostics of the plasma, an accurate and complete set of atomic structure data as well as of electron-impact excitation cross-sections across the wide range of energy is required. Hence, the present work aims to study the electron-impact excitations of few highly charged tungsten ions and report the excitation cross-sections as well as polarization of the subsequent decay of photon emissions of the excited ions. These results are expected to be the prime input for the diagnostics of ITER plasma.
Recently Tapasi et al. [2] have measured the spectra of Zr-like (W34+) to Se-like (W40+) tungsten ions using electron beam ion trap (EBIT) facility at the National Institute of Standards and Technology (NIST) in the wavelength range of 2.7-17.3 nm. On studying their observations, we have found that they have identified 15 new lines for which there are no theoretical or experimental data of excitation cross-section and polarization are available. In the light of this experiment, we have performed electron-impact excitation calculation using fully relativistic distorted wave theory (RDW) [3] for the new lines idetified by them. The relativistic bound state wave function of the tungsten ions in initial and final states are obtained by considering multi-configuration Dirac-Fock (MCDF) approximation by using GRASP2k code [4]. To assess the accuracy of the computed wave functions, we have compared our excitation energy and oscillator strength which we get while calculating wave function through GRASP2k code with the previously reported experimental and theoretical results. In addition, by using density matrix theory [5] and magnetic sublevel cross-sections, we have calculated the degree of linear polarizations of the emitted photons due to decay of the excited tungsten ions. To facilitate the plasma modelling calculations the obtained data of cross sections are fitted with multi parameter analytical functions. ________________
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[1] K. Ikeda, Nucl. Fusion 50, 014002 (2010). [2] T. Das, Y. A. Podpaly, J. Reader, J. D. Gillaspy, Y. Ralchenko, Eur. Phys. J. D 72, 124 (2018). [3] L. Sharma, A. Surzhykov, R. Srivastava, S. Fritzsche, Phys. Rev. A - At. Mol. Opt. Phys. 83, 1 (2011). [4] P. Jönsson, G. Gaigalas, J. Bieroń, C. F. Fischer, I. P. Grant, Comput. Phys. Commun. 184, 2197 (2013). [5] L. Sharma, A. Surzhykov, M. K. Inal, S. Fritzsche, Phys. Rev. A - At. Mol. Opt. Phys. 81, 1 (2010).
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Electron impact fine structure excitation of xenon and Plasma Modeling
Priti1*, R K Gangwar2 and R Srivastava1
1Indian Institute of Technology Roorkee, Roorkee-247667, India 2 Indian Institute of Technology Tirupati, Tirupati-517506, India
The xenon gas discharge is used in various plasma applications. In particular, xenon is used nearly in all modern HETs as propellant [1]. Also, mixture of inert gases including xenon is added to characterize the low temperature plasmas. The leading process in the low temperature xenon plasma is electron impact excitation of the various fine structure levels involved from the ground as well as excited states. For developing a reliable collisional radiative (C-R) plasma model, accurate electron impact fine structure excitation cross section data are required.
One can observe that there is still lack of sufficient cross section data of the electron excitations from the ground and among the excited states of xenon so that a reliable C-R model can be developed for xenon plasma. Even more recent results for the electron impact excitations are only from the ground state of xenon. Therefore, for the sake of providing sufficient consistent cross section data, detailed electron impact excitation cross section results for xenon in the wide range of incident energy from threshold to 1000eV are calculated using relativistic distorted wave (RDW) theory [2]. Various transitions from the ground 5p6 state to the excited 5p56s, 5p56p, 5p55d, 5p57s and 5p57p as well as among these excited states are considered. The relativistic Dirac-Fock multi-configuration wave functions for the ground and excited states of the xenon are obtained for the calculation. We have compared our cross section results, where available, with previously reported measurements and calculations to check the accuracy of our cross-sections. Using the obtained cross sections, a C-R model coupled with an optical emission measurement [3] from the inductively coupled Xe plasma is developed and the plasma parameters viz. electron temperature (Te) and electron density (ne) are extracted and reported.
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Fig1. Electron impact excitation cross-section for the transitions 1s0-1si (i=1-4). Solid line denotes the present RDW calculation; dashed line represents the BSR calculations [LxCat-https://fr.lxcat.net/data], and the symbols (square, sphere and triangle) show the experimental data of Filipovic et al. [Phys. Rev. A 37 356 (1988)].
[1] R A Dressler et. al., J. Phys. D. Appl. Phys., 42, 185203, (2009). [2] Priti et. al., Plasma Sources Sci. Technol.(In press) doi.org/10.1088/1361-6595/aaf95f [3] T Czerwiec et.al. J.Phys.D.Appl.Phys., 37,2827,(2004).
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Electron impact ionisation cross section for amino acids and benzene derivatives
N. Sinha1,*, D. Gupta2, A. Sahoo1 and B. Antony1,#
1 Atomic and Molecular Physics lab, Department of Applied Physics, IIT (ISM) Dhanbad, India 2 Plasma Technology Research Center, National Fusion Research Institute, South Korea
* [email protected] # [email protected] Electron collision processes are fundamental to any atmosphere due to the availability of enough free electrons to interact with molecules present. Such processes influencing the outcome of the local chemistry are of great significance for the understanding of these mediums. Ionisation plays an important role in the physiochemical processes that take place in such environments and hence is vital in modelling these atmospheres. However, the data available for electron collision with exotic systems are rather scarce. The measurement of electron impact ionisation cross section for complex molecules in the gas phase is very difficult. This is due to the practical difficulties involved in the preparation of well-characterized pure target gas and in the subsequent quantitative determination of the target densities. Thus to deal with the paucity of cross section data, development of simple and efficient theoretical models are encouraged. One of the well-known aromatic carboxyl acid is Benzoic acid. It is a fungistatic compound, widely used as a food preservative [1] and is an important precursor for the industrial synthesis of many other organic substances. Another exotic molecule selected here is Phenylacetylene. This alkyne hydrocarbon is supposed to be a likely product of the reaction of ethynyl radicals with benzene in the Titan’s atmosphere [2]. Ethylbenzene and n-propylbenzene with application in petrochemical [3] and printing/textile industry [4] are other hydrocarbons picked here. Further, amino acids are very important for human body [5]. In this work we have chosen glycine and Alanine as one among other targets. Apart from playing essential role in the metabolism of life on earth, they are also found in the interstellar medium [6, 7]. Surprisingly there is no previous literature available for these important compounds. We plan to present the first report of ionisation cross section for these molecules. We have utilized two different methods to compute the present cross section. Complex scattering potential-ionisation contribution (CSP-ic) [8] and binary encounter-Bethe (BEB) method [9] are applied to calculate the total ionisation cross section from the ionisation threshold of the target to 5000 eV. These two methods are among the most popular theoretical models to study the ionisation processes. CSP-ic method is based on the molecular structure and parameters; however BEB method deals with molecular orbitals. Thus a comparison of the two outcomes will offer a stringent way to check the accuracy of these theoretical models and further increase the credibility of the reported data. ________________ [1] F. Mota, I. Ferreira, S. Cunha et al., Food Chem. 82, 469-473 (2003). [2] B.Jones, F. Zhang, P. Maksyutenko et al., J. Phys. Chem. A 114, 5256-5262 (2010) [3] S. Yoon, J. Lee, S. Park, Appl. Therm. Eng. 27, 886-893 (2007) [4] J. Tang, K. Chu, L. Chan et al., Atmos. Pollut. Res. 5, 151-160 (2014)
P-36 [5] Y. Yu, R. Yang, D. Matthews et al., J. Nutr 115 (3), 399-410 (1985). [6] Shivani, P. Pandey, A. Mira et al., EPJD 71, 215 (2017). [7] Y. Kuan, S. Charnley, H. Huang et al., Astrophys. J 593, 848-867 (2003). [8] D. Gupta and B. Antony, J. Chem. Phys 141, 054303 (2014). [9] W. Hwang, Y. Kim, and M. E. Rudd, J. Chem. Phys. 104, 2956–2966 (1996).
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Electron impact elasticscattering cross sections of H2S D. Mahato1*, L. Sharma1 and R. Srivastava1
1 Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667 India *[email protected]
Studies on electron impact scattering from molecules are getting a lot of attention due to their involvement and applications in different physical and chemical processes. In the present work,we have considered electron scattering fromanon-linear,polar molecule ofHydrogen Sulphide (H2S) as a target. Due toits polar in nature, even the presence of a minor impurity, shows a significant effect on the physicalproperties of the gas, such as the electrical conductivity [1].H2S is used in the synthesis of semiconductors, such as in tungsten sulphide (WS2) [2] and also, in different plasma nitrocarburizing processes e.g. N2,H2 and H2S mixtures [3]. H2S is interstellar molecule and is found on the comet Austin (1989C1) [4]. H2S is also present in Earth’s atmosphere and identified as a major pollutant such as, inelectro chemical process like, corrosive processes in metal. Ananalytic method is used to obtain the charge density and static potential [5] of the multi-center target H2S. The molecular orbitalsare written as a linear combination of the atomic orbitals through STO-3G basis set. We have used an optical model potential approach to obtain elastic scattering cross sections.The model potential consists of the sum of static, exchange, correlation-polarization and absorption potentials. Using partial wave analysis method, the Schrödinger equation is solved for the projectile electron moving under the influence of this model potential and the scattering phase shifts are obtained with which the scattering amplitude is calculated.. There after the differential cross sections(DCS) calculated with the scattering amplitude. As an illustration our calculated DCS for H2S are shown in the Figure 1 below. The results are compared with the different measurements [4,6,7] as well as the available theoretical calculations [7]. Our resultsshow excellent agreement with previous experiments and theory.
Figure 1. DCS of H2S at 30 eV and 200 eV incident electron energies. ______________
[1]Bockelee-Morvan D, Colom P, Crovisier J, Despois D and Paubert G,Nature350 318(1991).
0 20 40 60 80 100 120 140 160 18010-2
10-1
100
101
Present P. Rawat et al. Marinkovicˇ Gulley et al.
Diffe
rent
ial C
ross
Sec
tion
(10-1
6 cm2 sr
-1)
Scattering angle (θ)
30 eV
0 20 40 60 80 100 120 140 160 18010-3
10-2
10-1
100
101
102
Present P. Rawat et al. P. Rawat et al.
Scattering angle (θ)
200 eV
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[2] R. Tenne, L. Margulis, M. Genut, G. Hodes, Nature360 444(1992). [3] C. Ruset, A.Bloyce, T. Bell, Surf. Eng.11 308(1995). [4]Gulley R J, Brunger M J and Buckmann S J, J. Phys. B: At. Mol. Opt. Phys.26 2913 (1993). [5] T. Das, A. D. Stauffer and R. Srivastava, Eur. Phys. J. D68, 4 (2014). [6] B. P. Marinkovic˘, Ph.D. thesis, University of Beograd, (1985). [7] P. Rawat, I. Iga, and M.-T. Lee, L. M. Brescansin, M. G. P. Homem and L. E. Machado, PRA.68, 052711 (2003).
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ELECTRON IMPACT EXCITATION OF HIGHLY CHARGED Ge LIKE Ba IONS
P. Malker1*, and L. Sharma1 1Indian Institute of Technology Roorkee
Atomic structure and collisional properties of the highly charged atomic ion have great importance in many areas of science and technology such as laser physics, plasma physics and astrophysics [1]. Since experimental studies on these systems are very limited, the requirement of atomic data is mostly fulfill by reliable theoretical methods. Moreover, the relativistic and QED effects play important role in the study of highly charged heavy ions. Therefore, in order to attain reliable results, these effects must be taken into account. Further, such studies become even more challenging for open shell Ge-like ions as there are several fine-structure levels in the ground state. There are only a few theoretical investigations for atomic structure properties of highly charged Ge-like ions. For example, recently Hao et al. reported excitation energies, transition rates and wavelengths for transitions from ground 4s24p2 to excited 4s4p3 and 4s24p4d states of Ge-like Te, Xe and Ba ions [2]. However, there are no results reported for electron impact excitation cross sections of the transitions considered in this work. In the present work we have performed extensive calculations of cross sections for electron impact excitation of Ge-like Ba XXV ions using fully relativistic distorted wave (RDW) method. We have considered fine-structure transitions between the ground state having configuration 4s24p2 and the excited states with configurations 4s4p3 and 4s24p4d. The reliability of our bound state wavefunctions is ascertained by comparing our results for excitation energies and oscillator strengths of the transitions with the available theoretical results of Hao et al. [2]. The initial and final state wavefunctions of the target ion is taken as multi-configuration Dirac Fock wavefunction [3]. The continuum wavefuncton for projectile/scattered electron is obtained by solving Dirac equation using spherically averaged potential of the ion is initial/final state of the ion as distortion potential. Thus, relativistic effects are incorporated in a consistent manner in our calculations. Finally, we obtained cross sections for all the 67 dipole allowed transitions considered in the present work. We have also provided fitting of our cross sections with the analytical form so that these can be used easily in plasma models. The detailed results will be presented in the conference. ________________ [1] J. D. Gilaspy, J. Phys. B: At. Mol. Opt. Phys., 34, R93 (2001). [2] L. H. Hao, X. P. Kang, and J. J. Liu. Journal of Applied Spectroscopy, Vol. 84, No. 2, May, 2017 (Russian Original Vol. 84, No. 2, March–April, 2017). [3] F.A. Parpia, C. Froese Fischer, I.P. Grant, Comput. Phys. Commun. 94 (1996) 249.
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Calculations for partial ionization cross sections for n-ethanol molecule by electron collision R. Singh*, Manoj Kumar and S. Pal
Department of Physics, M.M.H. College, Ghaziabad-201001 (UP) *[email protected]
Electron-impact ionization cross-sections for atoms and molecules are the most fundamental processes in collision physics. Keeping in the view of their importance, in the kinetics and dynamics of collisions and relevance in many practical applications such as gas discharges, plasmas, radiation chemistry, planetary upper atmospheres and mass spectrometry, the cross sections have been measured and calculated since the early days of collision physics. In the present work, we have evaluated the partial and total ionization cross sections as a function of incident electron energy for n-ethanol in the energy range from ionization threshold to 2000 eV. A semi empirical formulation [1-2] based on the Bethe formulation has been employed to calculate these cross sections There is a little study on partial electron scattering cross sections for ethanol molecule available on the theoretical and experimental sides. The presently calculated results for total ionization i.e. the sum of partial ionization cross sections are found in satisfactory agreement with the established experimental data sets [3-5] as shown in the figure.
Figure: Total ionization cross sections (TICS) for n-C2H5OH by electron impact. Solid line
– present calculations; experimental data: - [3], Ο- [4] and Χ- [2].
P-39 References: [1] R.Singh et al., J. Electr. Spectros. Related Phenom. 226 (2018) 22 and references therein. [2] K.L. Nixon et.al., Int. J. Mass Spectrom.404 (2016) 48. [3] J.E. Hudson et.al., Phys. Chem. Chem. Phys. 5 (2003) 3162. [4] R. Rejoub et.al., J. Chem. Phys. 118 (2003) 17.
P-40
Dissociative Electron Attachment to Jet Cooled Oxygen Molecules
Irina Jana, Varun Ramaprasad* and Dhananjay Nandi
Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India
Clusters of small molecules and atoms are important intermediates between gas phase and condensed phase. Formation of O! and O!2 ions via dissociative electron attachment to jet-cooled oxygen molecules has been studied using the time-of-flight technique. The jet-cooled molecules are produced by supersonic expansion using a nozzle mounted on a pulsed valve. Supersonic jet of O2 molecules containing weakly bound small van der Waals clusters seeded in a beam of Argon has been studied. The energy dependence of the !O and !O2 yield exhibits three resonances near 7, 11 and 16 eV incident electron energies. The 7 eV peak arises from the
2!Π u state of !O2 whereas, the 11 and 16 eV peaks are
ascribed to two distinct resonant states: !2Σ
+g and !
2Σ
+u states of !O2 respectively, via a
violation of the !Σ+ ⇋ Σ selection rule.
Fig 1. Ion-yield curves of !O and !O2 showing the three resonances at 7, 11 and 16 eV.
The dependence of the cross-section of these two new resonances at 11 and 16 eV on the proportion of the carrier gas is also investigated and an optimum proportion has been observed experimentally which results in the lowest parallel translational temperature of the beam. The results of this investigation and its implications will be discussed in this conference.
________________ [1] T. D. Märk, K. Leiter, W. Ritter, and A. Stamatovic, Phys. Rev. Lett. 55, 2559 (1985).
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[2] S. Matejcik, A. Kiendler, P. Stampfli, A. Stomatovic and T. D. Märk, Phys. Rev. Lett. 77, 3771 (1996). [3] R. Azria, L. Parenteau and L. Sanche, Phys. Rev. Lett. 59, 638 (1987). [4] E. Illenberger, Chem. Rev. 92, 1589 (1992).
P-41
Electron induced scattering from butane
Dineshkumar Prajapati1, 2*, Hitesh Yadav2, 3, Minaxi Vinodkumar3 and P. C. Vinodkumar2
1Shree M. R. Arts & Science College, Rajpipla, Gujarat, India 2Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Gujarat, India
3V. P. & R. P. T. P. Science College, Vallabh Vidyanagar, Gujarat, India
We present cross-section results for a study on electron scattering from butene. Elastic differential cross sections, integral cross sections, electronic excitation cross sections, momentum transfer cross sections, ionization cross sections as well as total cross sections have been computed at incident energies between 0.1 and 5000 eV with an ab initio R-matrix method at low-incident energies and the spherical complex optical potential formalism from intermediate to high energies [1-4]. The rate coefficients in the temperature range of 100– 10,000 K are also reported for this molecule.
Figure 1. e- butene total scattering cross sections
The present results are compared with the available data in the literature [5]. The detailed results and discussions will be done at the conference.Dr. Minaxi Vinodkumar acknowledges DST-SERB, New Delhi for major research project [EMR/2016/000470] for financial support under which part of this work is carried out. ________________ [1] J. Tennyson, Phys. Rep. 491, 29 (2010) [2] D. Prajapati, H. Yadav, P. C. Vinodkumar, C. Limbachiya, A. Dora, and M. Vinodkumar, Eur. Phys. J. D, 72, 210 (2018). [3] M. Vinodkumar, C. Limbachiya, H. Desai and P. C. Vinokumar, Phys. Rev. A 89, 062715 (2014)
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[4] H. Yadav, M. Vinodkumar, C. Limbachiya, and P. C. Vinodkumar, J. Phys. B: At., Mol. Opt. Phys., 51, 045201 (2018) [5] P. Moz˙ejko, E. Ptasin´ska-Denga, C. Szmytkowski and M. Zawadzki, J. Phys. B: At. Mol. Opt. Phys. 45 145203 (2012
P-42
Theoretical Studies Of Electron Impact on Formyl Fluoride
Tejas Jani1*, Hitesh Yadav1, 2, Dineshkumar Prajapati1, 3, Minaxi Vinodkumar2 and
P. C. Vinodkumar1 1Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Anand.
2Electronics Department, V. P. & R. P. T. P. Science College, Vallabh Vidyanagar, Anand. 3Shree M R Arts & Science College, Rajpipla.
A theoretical study on electron interaction with Formyl fluoride (HCOF) over a wide range of impact energies ranging from 0.1-5000eV. Owing to a wide range of impact energy, we are able to compute target properties and investigate a variety of processes and report data on resonances, differential cross section (DCS), momentum transfer cross section (MTCS), rate coefficient, total ionization cross section (TICS) [1] [2] and total scattering cross section (TSC). Due to the complexity involved in scattering calculation, two different theoretical formalisms are used. We have employed the ab-initio R matrix method via Quantemol-N for the lower energy range (0.1-20eV) and Spherical Complex Optical Potential (SCOP) beyond threshold energy of the target to 5000eV. We also used Binary encounter Bethe (BEB) model for calculating Total ionization cross section (TICS). The two methods are found to be consistent with a smooth cross over at 20eV. Some Theoretical data like Dipole moment [1], Rotational constant [2], Ground State Energy [1] are good agreement with exprimental data. Total excitation and inelastic cross sections of e – HFCO scattering for a wide energy range (0.1 to 5 keV) are reported for the first time, to the best of our knowledge.
Acknowledgement:
Minaxi Vinodkumar acknowledge DST-SERB, New Delhi for Major research project [EMR/2016/000470] for the financial support under which part of this work is carried out.
References:
[1] M. Vinodkumar, K .N. Joshipura, C. Limbachiya and Nigel Mason Phys. Rev. A 74, 022721 (2006) [2] H. Yadav, M. Vinodkumar, C. Limbachiya and P. C. Vinodkumar, Mol. Phy. 115:8 952-961 (2017) [3] TAE KYU HA and L.KELLER, Journal of Molecular Structure, 27, 225-232 (1975). [4] L. Margules and J. Demaison and James E. Boggs, J. Phys. Chem. A 103, 7632-7638 (1999)
P-43
Electron assisted elastic and inelastic processes for perfluoroketone (PFK) molecules
Mohit Swadia1, Nirav Thakkar2, Minaxi Vinodukmar3 and Chetan Limbachiya4,* 1 HVHP Institute of PG Studies and Research, Kadi-382 421
2Sheth M. N. Science College, Patan-384 265 3V.P. & R.P.T.P. Science College, Vallabh Vidyanagar- 388 120
4Dept. of Applied Physics, The M S University of Baroda, Vadodara- 390 001
*Email:- [email protected]
We report theoretical results of electron driven processes for PFK molecules over a wide energy range from ∼ ionization potential (IP) to 5000 eV. Perfluoroketone (PFK) gases are widely used in industry, e.g. as an insulating medium in high-voltage apparatus and as cleaning, etching, doping gases agent in vapor reactor [1,2]. Recently, these molecules have also gained much attention because of their low global warming potential (GWP). In industrial applications, while the gases composed of C3F6O, C4F8O, or C5F10O are used to generate gas discharge and low temperature plasmas, smaller PFK molecules CF2O and C2F4O are byproducts in plasma processes [2]. In all such plasmas, ionization caused by the collision between electrons and PFK molecules is one of the fundamental processes. The electron-impact ionization cross sections (Qion) are required to model the plasma processes and evaluate the insulating, radiating, or cleaning performance of PFK gases [2]. In order to describe the ionization processes in various plasmas resulting from PFK gases, the electron-impact ionization cross sections (Qion) of PFK molecules CxF2xO (x = 1-5) are calculated by Complex Scattering Potential-ionisation contribution (CSP-ic) method [3,4]. We have also calculated the total inelastic cross sections (Qinel) and total cross sections(Qtot) using the Spherical Complex Optical Potential (SCOP) method [3]. We propose to present all the results in detail at the conference. ________________ [1] Kesari et al. (2003) US Patent No. US 6,540,930 B2. United States, United State Patents. [2] Zhong et al., Plasma Sources Sci. Technol (2018) [3] Limbachiya et al., Mol. Phys., 113 (1), 55 (2015). [4] Vinodkumar et al., Int. J. of Mass Spect., 339–340, 16 (2013).
P-44
Emission and detection of energy selected electrons produced in low energy electron interaction with free Argon atom
Manish Kumar Singh1, S.Prajapati2, B.Singh2, S.Kumar1, 3, S.K.Singh1, B.K.Singh2, R.Shanker2
1Department of Physics, Indian Institute of Technology, Banaras Hindu University, Varanasi-221005
2Atomic Physics Laboratory, Department of Physics, Institute of Science, Banaras Hindu University, Varanasi-221005
3Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot, Israel-76100
Email address: [email protected]
Electrons are the central candidate in atomic, molecular and optical (AMO) physics. Outer shell electrons of an atom are having almost continuous energy, while inner shell electrons possess discrete energy characterizing the given atomic system. Emission of electrons from atoms or molecules produced under the collision of charged particle/photon has a large impact in many scientific areas like plasma physics, atmospheric science, biological spectroscopy, elemental analysis in material science, chemical physics etc. When any charged particle interacts with a single atom/molecule then as a consequence of momentum transfer from projectile to target, energy is transferred to the target which yields the emission of bound electrons from valence shell as well as from inner shell of the atom/molecule. In this present study, we have reported the emission and detection of inner shell electrons produced under the 3.5keV electron beam interaction with free Argon atom. The electron beam has been produced from the electron gun and parallel plate electrostatics and cylindrical mirror analyzer have been used for the energy selection and detection of the emitted electrons. The family of LMM Auger electrons of Argon having energy around 203 eV and other inner shell electrons having energy close to it has been detected and compared with the available theoretical results.
P-44
Figure: Energy spectrum of electrons produced under the impact of 3.5 keV electron beam with
Argon atom.
References:
[1] Sunil Kumar et al. Indian Journal of Physics , (July 2017) 91(7):721–72. [2] Sunil Kumar et al. EPJD, (2017) 71: 53.
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Triple Differential Cross Section for the electron impact ionization of atoms and molecules.
Nikita Dhankhar1*, Aditi Mandal1and Rakesh Choubisa1
1Department of Physics, Birla Institute of Technology and Science, Pilani, Pilani campus, Raj. 333031
In this communication, we present the results of the Triple Differential Cross Section (TDCS) for atomic and molecular targets. We use first Born approximation to compute TDCS for various kinematical arrangements. We describe the incident and scattered electrons by a plane wave, ejected electron by the Coulomb wave function and use different wave functions for the atomic and molecular targets. We benchmarked our numerical result with the established results in the literature (see Figure 1.) and is found to reproduce the earlier results [1]. We studied the electron impact ionisation (e,2e) of hydrogen molecular and the hydrogen atom. We are in process to compute TDCS with the twisted electron beam which contains additional orbital angular momentum and transverse momentum [2]. We propose to study the effects of the projection of the angular momentum of the twisted electron and the impact parameter on the angular profile of TDCS. We will present these results at the conference.
Figure 1. TDCS (a.u.) for the (e,2e) reaction for Eie = 250 eV, EB
e = 250 eV and θA = 3o , as function of θB for atomic Hydrogen.
P-45 ________________
[1] F. W. B. Jr, C. J. Joachain and B. Piraux, J. Phys. B 18,3203 (1985). [2] V. Serbo et al, Phys. Rev. A 92,012705 (2015).
P-46
Electron scattering total cross section of Butatrienylidene (H2CCCC): A cumulene carbene detected in interstellar medium
Nafees Uddin* 1, Pankaj Verma1 and Bobby Antony 1 1 Department of Applied Physics, IIT(ISM) Dhanbad, Dhanbad – 826004, Jharkhand, India
Butatrienylidene is a member of H2Cn species known as cumulene carbenes which have gained importance in astrophysical studies owing their presence in interstellar medium. The first three members of this series, vinylidene(H2CC), Propandienylidene (H2CCC) and Butatrienylidene (H2CCCC) are unstable, highly polar isomers of acetylene, cyclopropenylidene and diacetylene respectively, which are non polar. Electron scattering studies of cumulene carbenes are of prime importance to gain an insight to lesser known astrophysical phenomenon.
In the present paper we report the total cross section (TCS) of Butatrienylidene (H2CCCC), the third in the series of H2Cn species. The first detection of this molecule in the laboratory was reported by Killian et al [1] and subsequently detected astronomically in the circumstellar shell of IRC +10216 by Cernicharo et al [2] with IRAM 30 m telescope. Kawaguchi et al [3] detected the presence of Butatrienylidene in the dark TMC-1 molecular cloud.
The cumulene carbenes comprise of double bonded long chain carbon backbone with terminal unbonded carbenes The structure of H2CCCC as determined by Travers et al [4] is shown in Figure 1.
Figure 3. Structure of H2CCCC [4]
In this work, the total cross sections (QT) of H2CCCC on electron impact is calculated for incident energies (Ei) above ionization threshold (I) of the target to 5000 eV. Total inelastic cross section (Qinel) and elastic cross section(Qel)is evaluated using the well established Spherical Complex Optical Potential (SCOP) formalism [5]. QT is obtained by adding Qinel and Qel [6].
________________
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[1] Killian T, Vrtilek J, Gottlieb C, Gottlieb E, Thaddeus P, The Astrophysical Journal 365 , L89- L92(1990). [2] Cernicharo J, Gottlieb C, Guelin M, Killian T, Thaddeus P, Vrtilek J.,The Astrophysical Journal 368 , L39-L41(1991). [3] Kawaguchi K, Kaifu N, Ohishi M, Ishikawa S, Hirahara Y, Yamamoto S. , Astronomical Society of Japan, Publications 43(4), 607-619(1991). [4] Travers M, Chen W, Novick S, Vrtilek J, Gottlieb C, Thaddeus P., Journal of Molecular Spectroscopy,180(1), 75-80(1996). [5] R. Naghma, B.N. Mahato, M. Vinodkumar, B.K. Antony, J. Phys. B 44 , 105204 (2011). [6] Joshipura, K.N, Patel, P.M., Z Phys D 29, 269(1994).
P-47
Low temperature neon plasma Diagnostics with fully relativistic electron impact excitation cross-sections
S. S. Baghel1*, S. Gupta1, R. K. Gangwar2, R. Srivastava1
1 Department of Physics,Indian Institute of Technology Roorkee, Roorkee-247667 2Department of Physics,Indian Institute of Technology Tirupati, Tirupati-517506
The rare gas plasmas are often employed in fundamental studies to study the temporal and spatial characteristics of discharge kinetics. Further these plasmas are also suitable for developing various plasma based applications such as environmental remediation and sterilization etc. [1]. Electron induced atomic processes such as excitation plays a dominant role in the discharge kinetics of low temperature plasmas. Thus the reliable electron excitation cross-sections of inert gases are highly required for modeling and diagnostic purposes [2]. In the present work, we consider low temperature neon plasma for its diagnostic and calculate the electron impact fine-structure resolved excitation cross-sections of Ne atom from its ground and excited states. We use fully relativistic distorted wave (RDW) approach [3] for the calculations of the cross-sections and the neon is represented through the multi-configuration Dirac-Fock (MCDF) wave functions which are obtained from GRASP2K [4]. Further, by incorporating these cross-sections a Collisional-Radiative (CR) model has been developed for neon plasma for its diagnostic purposes. The model includes 40 fine structure states of neon corresponding to 2p53s, 2p53p, 2p54s, 2p54p and 2p53d configurations along with ground and ionic state. Besides electron-impact excitation process and radiative decay, diffusion of the ground and metastable states are considered in the model. Radiation trapping is also included in the model [5]. In order to extract the plasma parameters, the 1si level populations are optimized with corresponding measurements reported by Boffard et.al [6]. The extracted plasma parameters and derived emission intensity from CR model are obtained which are found in excellent agreement with the measurements [6]. The further details of the study along with theoretical procedure and results will be presented in the conference. .
[1] F F Chen, Phys. Plasmas 2, 2164 (1995). [2] J B Boffard, C C Lin, A E Wendt , Adv. At. Mol. Opt. Phy. 67,1-76 (2018) [3] R K Gangwar, L Sharma, R Srivastava, and A D Stauffer, Phys. Rev. A 81, 52707 (2010). [4] P Jönsson, G Gaigalas, J Biero’n, C F Fischer, and I P Grant, Comput. Phys. Commun. 184, 2197(2013). [5] R K Gangwar, Dipti, R Srivastava, and L Stafford, Plasma Sources Sci. Technol. 25, 035025 (2016). [6] J B Boffard, R O Jung, C C Lin, L E An. andA E Wendt, J. Phys. D: Appl. Phys. 45,38200(2012).
P-48
Measurement of angular distribution of Lα,β,γ x-ray intensity of Pt thick target following impact of 10-25 keV electrons.
B. Singh1, S.Prajapati1, B.K. Singh1 and R. Shanker1* 1 Atomic Physics Laboratory, Department of Physics, Institute of Science, Banaras Hindu
University, Varanasi-221005 *[email protected]
We present the new results on the angular distributions of Lα ,Lβ and Lγ x-ray line intensity of Pt (Z=78) thick target following impact of 10-25keV electrons. The angular measurements of the L-shell x-radiation were accomplished by rotating the target surface with respect to the electron beam direction [1]. The x-rays emerging from the target surface were detected by an energy dispersive Si P-I-N photodiode detector ( FWHM =200 eV at 5.9 keV). The resulting angular variation of x-ray intensity is considered to arise due to absorption of the radiation on its path through the thick target material as the absorption in the target depends on the depth within the target at which the radiation is produced as well as the take-off angle. We compare the experimental results with those obtained by PENELOPE MC calculations[2]; the agreement between experiment and theory is found to be satisfactory within uncertainties involved in the measurements and the theoretical results.
________________ [1] B. Singh, S. Kumar, S. Prajapati, B. K. Singh, X.Llovet and R. Shanker, J. of Elect. Spectr. and Rel. Phen.21617 (2017). [2] F. Salvat PENELOPE-2 014 A Code System for Mionte Carlo Simulation of Electron and Photon Transport (2015).
P-49
Effect of strong magnetic field on optical emissions from atmospheric pressure micro-plasmas
Kalyani Barman1, Deepika1, Mohit Mudgal1, Sudeep Bhattacharjee1*, Ramkrishna Rane2 and S.K. Nema2
1Department of Physics, Indian Institute Technology Kanpur, Kanpur-208016 2HBNI, FCIPT, Institute for Plasma Research, Gandhinagar-382016
Atmospheric pressure micro-plasmas are non-equilibrium plasmas with widely different electron (~ 0.5 eV) and ion temperatures (~ 0.025 eV). These plasmas have versatile applications in fields such as biology, surface modification, environment and medicine. The micro-plasmas can be easily created in the atmosphere in the form of a dielectric barrier discharge, inside a quartz micro-capillary. The plasma emerges from the capillary in the form of a fine plasma jet. The inner and outer diameter of the capillary tube is 3 mm and 5 mm respectively. The applied voltage has a maximum value of 4.2 kV and the frequency can be varied in the range 80 -100 kHz. A coaxial pin of diameter 1.6 mm forms the high voltage electrode and a copper ring of diameter 5 mm is used as the ground electrode. The high voltage pin lies in the center of the capillary and extends up to the exit of the capillary, the copper ground electrode is wound around the exit region of the capillary. The gas flow rate is maintained in the range 3 - 5 lpm. Two bar magnets having dimensions 5 cm x 3 cm x 2 cm and a surface magnetic field of 4000 Gauss have been used to create a transverse magnetic field to the jet. The plasma jet is positioned at the center of the two magnets. The optical emission spectroscopy (OES) of the jet represent different emission lines [1] of helium, molecular nitrogen, nitrogen ionic lines, oxygen, including H-α and H-β lines of hydrogen. The electron density has been measured from the stark broadening of the H-α lines [2] and the electron temperature has been measured from the Boltzmann plot [3]. The spectrum is captured under several conditions: (a) without magnetic field and, (b) under varying values of magnetic field, which is achieved by moving the magnets either closer or farther away from the jet. The aforementioned plasma parameters, and the evolution of the spectral lines are determined and investigated for each case. It is found that upon application of a magnetic field, the ionic lines which are present in the optical emissions get enhanced. It is also observed that the molecular lines are enhanced but to a lesser extent. However, the amplitude of the atomic lines remains unchanged. When a strong magnetic field is applied to the plasma jet in a transverse direction to the plasma flow, the trajectory of the particles deviates from its original path, and can move in helical paths due to the Lorentz force [4], thereby increasing the dwell time in the jet with possibility of further ionization. ________________ [1] M. Thiyagarajan, A. Sarani and C. Nicula, J. Appl. Phys. 113, 233302 (2013)
[2] A Yu Nikiforov, Ch Leys, M A Gonzalez and J L Walsh, Plasma Sources Sci. Technol. 24 034001(2015) [3] D. Mariotti, Y. Shimizu, T. Sasaki and N. Koshizaki, Journal of Applied Physics 101, 013307 (2007) [4] P. Zhu, Z. Meng, H. Hu and J. Ouyang, Physics of Plasmas 24, 103512 (2017)
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Study of Electron interactions with Plasma Processing gases Rakesh Bhavsar1, Yogesh Thakar1, Dhaval Chauhan2,Chetan Limbachiya2,*
1M.N. College, Visnagar -384315 2The M.S. University of Baroda, Vadodara – 390001
*E-mail:[email protected]
We report electron impact inelastic, ionization and excitation cross sections for plasma processing gases like TiClx, x =1,2,3,4 and CFy, y=1,2,3,4 from ionization threshold to 5 keV.The plasma phase exclusive properties provide powerful remedy to a number of industrial and manufacturing problems. Plasma processes plays important role in fabrication of devices like LEDs [1]. In semiconductor etching, plasmas can give access to chemically active species ions and radicals from a relatively inert feed gas[1].The industry relies upon the development of plasma technology to produce progressively more detailed and compact systems while also meeting increasingly severe environmental legislation. Technological plasmas are partially ionized, partially dissociated gases. They contain electrons, atomic ions, molecular ions, and neutrals [2]. We have employed Spherical Complex Optical Potential (SCOP) [3] to calculate total inelastic cross sections Qineland have used Complex Scattering Potential – ionization contribution (CSP-ic)[4] formalisms to compute total ionization cross sections Qion and summed total excitation cross sections ∑Qexc. We have compared our cross sections with available experimental as well as theoretical results and have found good agreement wherever available.
Key Words: plasma processinggases, ionization cross sections, spherical complex optical potential, complex scattering potential-ionization contribution.
[1] N. T. Kalyani, S. Dhoble, Renewable Sustainable Energy Rev. 16(2012) 2696. [2] I. Rozum, P.Limao-Vieira, S.Eden, J.Tennyson and N.Meson, American Institute of Physics.35 (2006) 267 [3] MohitSwadia, et al.,Molecular Physics, 115, 2521-2527 (2017) [4] M. Swadia, Y. Thakar, M. Vinodkumar, and C. Limbachiya, Eur. Phys. J. D.71, 85(2017)
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Estimation of total erosion yield of graphite limiter in ADITYA-Upgrade tokamak
Ritu dey1,*, M. B. Chowdhuri1, R. Manchanda1, and N. Yadava2 , J. Ghosh1,3 1 Institute for Plasma Research, Bhat, Gandhinagar 382 428, India
2Gujarat University, Navrangpura, Ahmedabad 380 009, India 3Homi Bhaba National Institute, Training School ComplexAnushakti Nagar, Mumbai 400 094,
India *[email protected]
The edge plasma provides good thermal insulation and prevents impurity influx from destroying the burning core plasma of tokamak. In addition, the wall surface of various tokamaks plays an important role in the recycling of hydrogen isotopes, and in plasma fuelling. In our earlier study of neutral particle dynamics in ADITYA tokamak, the plasma-material interaction processes, such as reflection, desorption and physical sputtering, are included while chemical sputtering is not being considered [1]. Considering lower edge temperature of ADITYA-Upgrade (ADITYA-U) tokamak plasma chemical sputtering may play an important role. While carryout such study in the ADITYA-U tokamak, which is a medium sized tokamak with graphite limiter and the temperature of limiter surface is around 60o C at a first step, erosion yield has been evaluated. In the present work, total erosion yield [2] is estimated using analytical form of chemical erosion process including physical sputtering as well as chemical sputtering process. It is to be noted that the energy deposition leading to atomic displacements with corresponding breaking of C-C bonds lead to an increase of chemical erosion. Presently, chemical erosion of Carbon due to hydrogen, carbon and oxygen ions are estimated for ADITYA-U tokamak.
Figure 1. Erosion yield vs surface temperature for various ion fluxes. Figure 1 shows the variation of total erosion yield as a function of surface temperature for various incident ion fluxes. It is worth to mention that for ADITYA-U
P-51 tokamak plasma, the estimated incident ion flux using particle confinement time and is 2x1020 m-2s-1. At 323 Kelvin and the above mentioned ion flux the erosion yield comes out to be 7.06x10-3. From the figure, one can notice that yield is constant upto temperature 600 Kelvin. After that yield increases to a peak value at temperature of around 800 K and then decreases further. Also, when the flux surfaces increases the peak is shifted towards the larger surface temperature. The details of the investigation will be presented at the conference. [1] DeyRitu et al, Nuclear Fusion 57, 086003 (2017). [2] J. Roth, Journal of Nuclear Material 266, 51 (1999).
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Collisional radiative model for Ar/N2 mixture plasma with fine structure resolved electron impact excitation cross sections
Shivam Gupta1*, R.K. Gangwar2 and Rajesh Srivastava1
1 Department of Physics, Indian Institute of Technology Roorkee, Roorkee-247667, India 2Department of Physics, Indian Institute of Technology Tirupati, Tirupati-517506, India
The diagnostics of non-equilibrium plasmas of argon with reactive gases (viz. N2, O2 and CH4) have created increased interest due to its industrial and technological applications. Therefore, it is essential to study in more detail how the mixing of reactive gases in the argon gas plasma influences the plasma parameters viz. electron density (ne) and electron temperature (Te). In the present work, Ar/N2 mixture plasma has been studied. For this purpose fine structure resolved collisional radiative (CR) plasma model is developed for the diagnostics of Ar/N2 mixture plasma [1]. In the model 40 fine structure levels of 3p54s, 3p54p, 3p55s, 3p55p and 3p54d configurations of argon are considered. A complete set of fully relativistic distorted wave cross sections for several fine structure transitions are utilized in the model [2]. CR model considers non-Maxwellian electron energy distribution for the entire calculation. In the model, we incorporate various populating and depopulating channels for the accuracy of plasma parameters (viz. electron temperature (Te) and electron density (ne)). Particle balance equations are solved to get the populations of the excited levels and their emissions are matched with Lock et al.[3] measurements to get the plasma parameters.
Figure 1. Comparison of plasma parameters with measurement and model of Lock et
al [3] for Ar/N2 (0–10%) mixture plasma. We find from our study that as the concentration of N2 increases from 0-10%, the extracted ne varies from 2.3×1011 to 2.8×1011 cm-3 and Te decreases from 1.0 to 0.43 eV. The details of the CR model along with the complete results [1] will be presented in the conference.
________________
[1] S. Gupta, R. K. Gangwar and R Srivastava, SpectrochimicaActa Part B 149, 203-213 (2018). [2] R K Gangwar,L Sharma,R Srivastava and A D Stauffer,J. Appl. Phys.111, 053307 (2012). [3] E H Lock, Tz B Petrova, G M Petrov, D R Boris and S G Walton, Phys. Plasmas 23, 043518 (2016).
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Spectroscopic Studies of Cold Atomic Hydrogen inAditya-U Tokamak Edge
Nandini Yadava1*, J. Ghosh2,Sripathi Punchithaya K1,M. B. Chowdhuri2, R. Manchanda2, S. Banerjee2, Ritu Dey2and Aditya-U team2
1National Institute of Engineering, Mysuru 570008, India 2Institute for Plasma Research, Bhat, Gandhinagar 382 428, India
Spectroscopic measurements of Balmer alpha line profiles of atomic hydrogen, emitted within the edge region of the Aditya-U tokamak plasma has been carried out. As the tokamak plasma is subjected to high magnetic fields, Zeeman spectroscopy has proved to be a valuable method, not only of impurity identification and analysis, but also of studying some fundamental atomic processes in the edge region of tokamak plasmas in tokamaks[1]. From Zeeman spectroscopy, estimating the neutral temperatures using spectral line (656.28 nm) revealed that there exists poloidal asymmetry in neutral temperatures for Aditya-U tokamak. The hydrogen spectra indicate that the hydrogen atoms have different temperatures in the edge region of ADITYA-U tokamak. The ‘cold’ atoms are the atoms heated by elastic collisions with background ions/molecules, whereas ‘warm’ atoms are due to the Frank-Condon moleculardissociation and third group of ‘hot’ atoms are produced directly by charge-exchange recombination between ‘hot’ protons and boundary region atoms. In this paper, we looked into the asymmetry in the cold and warmcomponents of the excited neutral hydrogen, whose probable origin has been ascribed to electron impact-induced molecular dissociation. Theelastic atom-ion collisions and their role to modify the edge plasma parameter for Aditya-U tokamak is discussed. ________________ [1] D. Hey, J & C. Chu, C & Hintz, E. (2000). Spectroscopic Studies of Cold Atomic Hydrogen and Deuterium Produced in a Tokamak Edge Plasma. Contributions To Plasma Physics - CONTRIB PLASM PHYS. 40. 9-22.
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Structural behaviour of diamagnetic cavity in laser-produced plasma
Narayan Behera*, R. K. Singh and Ajai Kumar Institute for
Plasma Research, Bhat, Gandhinagar - 382 428, India * [email protected]
The theoretical and experimental investigation of diamagnetism in laser-produced plasma has been done extensively in the recent past. When laser-produced plasma expands in transverse magnetic field, the plasma plume takes shape as a form of a cavity or bubble, known as magnetic bubble. Through the most of the experiment have been used permanent bar magnets which have the experimental limitations. Plasma imaging along the magnetic field lines is not possible in case of permanent bar magnet, which is essential to get a three dimensional structure of the evolving diamagnetic cavity. This problem has been effectively resolved by replacing the permanent bar magnets with a Helmholtz coil which facilitates plume imaging along and across the magnetic field simultaneously. In this setup, two internally synchronized ICCD cameras, mounted in a direction orthogonal to the plume propagation has been used to capture two directional images of the plume. An Nd:YAG laser (λ = 1064 nm, 8 ns pulse width) has been used to generate plasma plume in the presence of transverse uniform magnetic field, varying from 0 to 0.57 T. Three-dimensional structure of expanding plasma plume as well as induced diamagnetic cavity have been obtained by adding the sequence of images of the plasma plume projected in two orthogonal directions (i.e., along and across the magnetic field lines). We have observed an elliptical cylinder-like diamagnetic cavity in contrast to the theoretically predicted spherical one. A theoretical model has also been developed to explain the observed features of diamagnetic cavity. Details of developed technique and physics involved in observed diamagnetism will also be discussed.
References [1] D. Winske, Phys. Fluids B 1, 1900 (1989). [2] Narayan Behera, R. K. Singh and Ajai Kumar, Phys. Lett. A 379, 2215 (2015). [3] Narayan Behera, R. K. Singh, V. Chaudhari and Ajai Kumar, Phys. Plasmas 24, 033511 (2017). [4] Narayan Behera, R. K. Singh and Ajai Kumar, Frontiers in Optics / Laser Science, OSA Technical Digest (Optical Society of America, 2018), paper JW3A.37.
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Electronic state spectroscopy of methacrolien Sunanda K.1*, A. K. Das1,2 and B.N. Rajasekhar1,2
1 Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085 2 Homi Bhabha National Institute, Anushaktinagar, Mumbai-400 094
Methacrolien (MC) has been an important volatile organic compound in atmosphere derived primarily from oxidation of isoprene through radicals like OH, NO3, O3 and is one of the abundant non-methane hydrocarbon released into the troposphere from biogenic emission [1]. MC plays a very significant role in tropospheric ozone production, thus recent studies were dedicated to the investigation of gas phase oxidation of MC [2]. Low resolution photoabsorption cross-sections of MC reported earlier [3] cover UV-VUV region consisting of a broad continuum in the UV region (~210 nm) followed by sharp peaks up to 120 nm lie in the VUV region, giving rise to a complex absorption spectrum. In this work, the focus is to obtain detailed spectroscopic information of MC in 105 -270 nm region encompassing first few ionization potentials. For this purpose, high resolution gas phase photoabsorption experiments are carried out using synchrotron radiation from Indus-1 SRS and a stainless steel absorption cell (maintained at a base pressure 10-6 mbar) coupled to the Photophysics beamline [4]. Quantum chemical calculations were performed using density functional theory (DFT) for ground state geometry optimization and time dependent DFT (TDDFT) for vertical excited state estimations using GAMESS code [5]. The simulations helped in predicting and identifying valence and Rydberg excitations predominantly from the first two highest occupied molecular orbitals of the molecule converging to the first two ionization potentials. A preliminary view of the experimental observation, theoretical results and interpretation of the spectral features will be presented. _________________ [1] Guenther et.al., Atmos. Chem. Phys. 6, 3181-3210 (2006). [2] Mellouki et.al. Chem. Rev. 115, 3984-4014 (2015). [3] Lee et.al. J. Phys. Chem. A 111, 11948-11960 (2007). [4] B.N. Rajasekhar et.al. J Chem. Phys., 139, 064303-1 (2013). [5] GAMESS(USA), J Comp. Chem. 14 (11), 1347-1363 (1993).
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Spectroscopic studies on Crotonaldehyde in the VUV region
A. K. Das1,2*, S. Krishnakumar1,2 and B.N. Rajasekhar1,2
1 Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085 2 Homi Bhabha National Institute, Anushaktinagar, Mumbai-400 094
Crotonaldehyde (C4H6O) attracts the attention of many spectroscopists in early years for its wide industrial applications: such as manufacturing of sorbic acid, a food preservative, yeast and mold inhibitor. It is also used as a warning agent in gas fuels to detect small leakages, in preparation of rubber accelerators, in leather tanning, as alcohol denaturant and as a stabilizer for tetraethyl lead. It is a raw material for trimethylhydroquinone: a precursor to pharmaceuticals, dyes and pesticides [1-3]. Existing literature on this molecule include vibrational spectroscopic data, ultraviolet absorption [4, 5]. However, it has been observed that electronic data and thermodynamic parameters at various temperatures, which are vital to elucidate the relations among energetic, structural and reactivity of the title molecule, are insufficient in the literature. Also a detailed quantum chemical study on the observed FTIR and FT-Raman spectra of crotonaldehyde has not been ornately reported so far. Hence in this paper a detailed UV-VUV photoabsorption study of crotonaldehyde is taken up. Gas phase photoabsorption experiments in the 105-270 nm regions are carried out at Photophysics beamline, Indus-1, a 450 MeV SRS [6]. Sample is introduced into an SS absorption cell maintained at a base pressure 10-6 mbar. Spectra are recorded at several pressures in the range 0.1 mbar to ~ 10-4 mbar to take into account the varying absorption coefficient. Theoretical computations were carried out using density functional theory (DFT) using GAMESS (USA) code [7]. Photoabsorption spectrum of crotonaldehyde comprise of few valence transitions followed by Rydberg series and accompanying vibronic transitions. Background absorptions underlying some of the Rydberg bands may be attributed to high lying valence states. Assignments of electronic transitions are aided by TDDFT computations of vertical excited states and DFT computations of vibrational frequencies in the neutral and ionic ground states. Experimental observations, theoretical results and interpretation of the spectral features are discussed. ________________
[1] E. R. Coburn, Org Synth Coll., 3, 696 (1955). [2] J. E. Fernandez, T. W. G. Solomons, Chem. Rev., 62, 485 (1962) [3] S. S. Hecht, E.J. McIntee, M. Wang, Toxicology, 166, 31 (2001) [4] Jayaprakash, V. Arjunan, S. P. Jose, S. Mohan, Spectrochim Acta A, 83, 411(2011) [5] A. M. D. Lee et al., J. Phys. Chem. A, 111, 11948 (2007) [6] http://www.rrcat.gov.in/technology/accel/srul /indus1beamline/photophysics.html [7] M. W. Schmidt et al., J. Comp. Chem., 14, 1347 (1993)
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Vibrational Spectroscopic studies on 2,3-Dihydrobenzofuran-5-carboxaldehyde
D.Vijay1, Asim Kumar Das2, B N Rajasekhar2 and A.Veeraiah1* 1Molecular Spectroscopy Laboratory, Department of Physics, D.N.R. College (A), Bhimavaram, India-
534202 2Atomic & Molecular Physics Division, BARC, Mumbai , India
*Corresponding author: [email protected]
Abstract: The titled compound, "2,3-Dihydrobenzofuran-5-carboxaldehyde" was optimized using B3LYP hybrid functional implementing the standard 6-31G(d, p) basis set and higher basis set 6-311++G(d,p). Vibrational frequencies, structural geometry and Potential energy surface (PES) scan analysis were carried out. Normal and higher basis set results were analyzed and reported. The predicted IR intensities (4000-400 cm-1) and Raman activity(4000-100 cm-1) were compared with experimental results. Scaled and Unscaled frequencies were reported with the respective Potential energy distributions. NBO, NLO and frontier molecular orbital analysis were also carried out using the both basis sets. TD-DFT calculations were performed on the titled compound and compared with the observed spectrum. From UV-Vis spectrum, absorbance maxima was observed at 336 nm which shows good coherence with the predicted maxima. Molecular orbital interactions (HOMO-LUMO) analysis, Molecular electrostatic potential maps (MESP), thermodynamic properties, Mulliken atomic charge population analysis, etc., were also carried out and reported.
Keywords: 2,3-Dihydrobenzofuran-5-carboxaldehyde (DBC), DFT, FT-IR, UV-Vis spectra, fluorescence spectra ________________
[1] Mikael Elofsson, European Journal of Medicinal Chemistry 143, 1077 (2018) [2] X. Jiang, W. Liu, W. Zhang, F. Jiang, Z. Gao, H., Eur. J. Med. Chem., 46, 3526 (2011) [3]Venkatesh T ,Bodke YD ,Joy MN , Dhananjaya BL,Venkataraman S, Iranian journal of pharmaceutical research (IJPR) 17(1), 75 (2018)
[4]A. Veeraiah, Kadali Chaitanya, V. Veeraiah, M.V.S. Prasad, N. Udaya Sri, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95, 648 (2012)
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Studies on electronic and vibrational spectroscopic properties of propanol structural isomers
**Paramjeet Singh1, Sunanda K.1, Asim Kumar Das1 A.P.Mishra1, 2 and *B.N. Rajasekhar1,2
1 Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085 2HomiBhabha National Institute, Anushaktinagar, Mumbai-400 094
**[email protected],*[email protected]
Synthesizing bio-fuels from renewable sources is the requirement of the day in terms of new energy sources and environmental problems. Towards this endeavour, studies on ethanol and higher alcohols (both straight chained and branched chain) have showed promising results as new gasoline substituent [1]. To understand the chemical processes one need accurately know the molecular constants. With this aim, a study of electronic and vibrational spectroscopic properties of propanol which is found in 2 structural isomeric forms; normal (n) propanol (CH3CH2CH2OH) and iso-propanol [(CH3)2CHOH] are taken up. The effect of positioning of OH group leading to the formation of structural isomers of propanol and its effect on excited state structure of isomers of different chemical activity is the objective of this study. Energetic changes arising due to the conformers on the electronically excited states are expected to assist in understanding of the bond dissociations and pathways.
Fig. 1 : Electronic spectra of n-propane
Quantum chemical calculations using DFT methodology for the ground state are carried out to obtain the geometries of the propanol isomers. Excited state energies, Potential energy curves of the first few excited states with respect to specific bond stretching coordinates and other related issues are addressed with the help of TDDFT calculations. Theoretical computations were carried out using GAMESS (USA) code [2]. The only early work reports the UV-VUV absorption spectrum reports at moderate resolution but does not offer any spectral analysis [3]. Fig.1 shows the theoretical excited state energies and low resolution (4Ǻ) spectrum of n-proponal [3, 4]. Results and detailed analysis of experimental and theoretical spectroscopic properties of isomers of propanols will be discussed in this poster.
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[1] Shota Atsumi et.al. 451| Nature 06450 (2008). [2] M. W. Schmidt et al., J. Comp. Chem.,14, 1347 (1993). [3] D.R. Salahubz and C, Sandorfy, Chem Phys. Lett. 8 71 (1971). [4]The MPI-Mainz (www.uv-vis-spectral-atlas-mainz.org).
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Nanoparticle enhanced LIBS of Cu target using pulsed Nd: YAG laser as excitation source
Swetapuspa Soumyashree*, Nageswara Rao E., Prashant Kumar, Pooja Chandravanshi, Madhusudhan P, Rajesh K. Kushawaha, S.B. Banerjee,
K.P. Subramanian
Physical Research Laboratory, Ahmedabad-380009, India
Role of Aluminum (Al) nanoparticles on enhancement of emission spectra in Laser Induced Breakdown Spectroscopy has been investigated using the Nd: YAG laser of 532 nm wavelength and 7 ns pulse duration, various concentrations of Al-nanoparticles deposited on Cu-substrate and Andor Echelle Spectrometer. Solutions of different Al-NPs concentrations viz., 0.1, 0.2 and 0.8 mg/ml were made by dispersing 1 mg of Al NPs in 10, 5 and 1.25 ml of acetone and 0.4 mg/ml solution by dispersing 2 mg of Al NPs in 5 ml of acetone. For each concentration of Al nanoparticles deposited on Cu substrate, the experiment was performed at different gate delays to understand the signal enchantment mechanism. The 2-3 times enhancement in emission spectra of Cu sample has been observed. A comparison of LIBS and Al-NPs LIBS spectrum is shown in figure in which enhancement by NPs is clearly seen.
Figure 1: Comparison between LIBS and NELIBS spectra of Brass target
[1] A.D. Giacomo et al., Analytical Chemistry, 85 (2013) [2] S. Abdul Kalam et al., OSA 2016
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Estimation of elemental concentration using plasma emission spectroscopy employing synthetic spectrum method
E. Nageswara Rao*, Prashant Kumar, Swetapuspa Soumyashree, Pooja Chandravanshi, Rajesh K Kushawaha, Swaroop Banerjee and K P Subramanian
Physical Research Laboratory, Ahmedabad-380009, India
In the present study, we have estimated the elemental concentrations of Al, Ca, Fe, Mg, Mn,
Na, Si, and Ti present in basalt rock sample by laser induced breakdown
spectroscopy (LIBS). A Q-switched Nd:YAG laser was used at 1064 nm, ~7 ns, ~10
Hz, ~400 mJ for the LIBS experiment. All estimated elemental compositions
matches well with the reference values acquired from the X-ray fluorescence (XRF)
spectroscopy. Time resolved spectra were also recorded from 500 ns to 7000 ns
delay after plasma initiation to understand the effect of background level on the
detection limits for the elements. Simulated emission profile based on local
thermodynamic equilibrium (LTE) model at different concentrations was generated
for two minor elements present in the sample. These simulated line profiles were
then compared with the experimental value to understand the non-appearance of
some elements in the LIBS spectrum. This technique can thus be useful in
predicting the detection limit for different elements.
Fig. The matching experimental LIBS spectra (orange color) and synthetic generated spectrum (blue) of basalt rock sample.
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1. Ciucci, M. Corsi, V. Palleschi, S. Rastelli, A. Salvetti, E. Tognoni, Appl. Spectrosc.53(8): 960–
964(1999). 2. Prashant Kumar, R.K. Kushawaha, S.B. Banerjee, K.P. Subramanian, N.G. Rudraswami,
Appl. Opt. 57(19): 5443–5450(2018).
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IR attenuation due to phase changes from amorphous to crystalline in astrochemical propargyl ether ices
K. Rahul1, J Meka1, A Das2, B N Raja Sekhar3, B – M Cheng4, N J Mason5, B Sivaraman1*
1 Physical Research Laboratory, Ahmedabad, India 2Indian Center for Space Physics, Kolkata, India
3RRCAT, Indore, India 4National Synchrotron Radiation Research Centre, Hsinchu, Taiwan
5University of Kent, Canterbury, United Kingdom *[email protected]
InfraRed (IR) spectroscopic technique plays a vital role in the study of interstellar molecules both space-based and in laboratory simulations. Spitzer space telescope operating in the Mid and Far IR wavelength is widely used to understand the icy nature of molecular clouds and their chemical composition. By comparing the spectral features between space-based data and laboratory ice analogues it is possible to deduce the chemical heterogeneity that is present in the dusty cold environment of the ISM. Therefore, laboratory analogues and their corresponding IR spectra are imperative for probing molecular ices in the ISM. While investigating the astrochemical ices and their corresponding IR spectra at lower temperatures, usually the broad absorption features seen at 10 K after sample deposition is attributed to the amorphous phase. After deposition, the ices are warmed gradually or at a fixed heating rate (such as 0.5 to few K s-1) with subsequent recording of IR spectra. Subtle changes appearing in the IR spectra during the warmup phase are related to the conformational changes related to homodimers [1]. However, significant changes that appear in the spectra, such as band splits along with the appearance of sharper bands, are related to the phase change from amorphous to crystalline that had taken place within the ice. Recently, by observing such changes in the IR spectra reversible phase change was reported to occur in astrochemical ethanethiol ices [2]. However, to-date, significant attenuation of IR photon intensity due to phase change was not reported. In this present study, propargyl ether (C3H3OC3H3), an isomer of phenol (C6H5OH) which is reported to be present in the Orion KL [3] using the IRAM 30m telescope, is the molecule of interest. Therefore, propargyl ether is regarded as one of the interesting molecules, awaiting discovery in ISM, in understanding the chemical complexity that surrounds the evolution of aromatic molecules in icy mantles. Current laboratory experiments on propargyl containing compounds are limited to the study of propargyl alcohol ices [4-6]. To-date no IR and Vacuum UltraViolet (VUV) spectroscopic data are available for propargyl ether ices at temperatures commensurate with the ISM. Accordingly, propargyl ether IR and VUV spectra are recorded as a function of temperature and the observations made in both the amorphous and crystalline phases of propargyl ether will be discussed. ________________ [1] B. Sivaraman et al., Spectrochim. Acta A: Mol. Biomol. Spectrosc., 105, 238 (2013).
P-61 [2] S. Pavithraa et al., Spectrochim. Acta A: Mol. Biomol. Spectrosc., 178, 166 (2017). [3] L. Kolesnikova et al., J. Mol. Spectrosc. 289, 13 (2013). [4] B. Sivaraman et al. ApJ, 798, 72 (2015). [5] J. Saini & K. S. Viswanathan, J. Phys. Chem. A, 121, 1448 (2017). [6] R. L. Hudson & M. H. Moore, ApJ, 857, 89 (2018).
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Reversible phase change observed in 1-hexyne astrochemical ices
J Meka, K Rahul, B Sivaraman* 1 Physical Research Laboratory, Ahmedabad, India
Icy dust grains in the InterStellar Medium (ISM) are very well known to be the tiny chemical factories that are responsible for the synthesis of variety of complex molecules, both organic and inorganic, that are observed to-date and those awaiting identification. Perhaps, due to advent of space telescopes the molecular icy mantles on dust grains are also studied at InfraRed (IR) wavelengths and are compared with the laboratory based spectra. Existing spectral repository of simple molecules suggest that the morphology of astrochemical ices can be either amorphous or crystalline. In fact, IR spectroscopy of astrochemical ices are quite sensitive to the changes in morphology. Laboratory ice analogues of simple and complex molecules, that are made by recreating the pressure and temperature conditions of the ISM, probed using IR spectroscopy has clearly shown the existence of amorphous phase when molecules are deposited at very low temperature, say 10 K, and then a phase change to crystalline ice to occur by warming the ice to higher temperatures. Indeed, warming the ice to temperatures above the crystalline phase results in the sublimation of the molecular ice as it is kept at ultra-high vacuum condition. However, recently a reversible phase change in ethanethiol astrochemical ices was observed where the ice subjected to temperature cycle was observed to switch morphology from amorphous to crystalline then back to amorphous [1]. Following the first report on reversible phase change, Hudson [2] reported similar change to occur in the ethanol ices too suggesting there may exist more such molecules that undergo the reversible phase change. In our recent experiments using 1-hexyne [HCC(CH2)3CH3] we observed similar reversible phase change to occur. In this meeting, we will be presenting the results from the detailed work carried out on 1-hexyne pure ice and the mixtures of 1-hexyne with water. ________________ [1] S. Pavithraa et al., Spectrochim. Acta A: Mol. Biomol. Spectrosc., 178, 166 (2017). [2] R. L.Hudson, Spectrochim. Acta A: Mol. Biomol. Spectrosc., 187, 82 (2017)
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The AstroChemical Ices Database (ACID) and its access through SSHADE
V.Bhushit1,*, K. Rahul1, M. Dinesh1, L. Chetan2, B –M Cheng3, N J Mason4 and B Sivaraman1
1Physical Research Laboratory, Navrangpura, Ahmedabad, India 2Department of Applied Physics, The M. S. University of Baroda, Pratapgunj, Vadodara,
India 3National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
4University of Kent, Canterbury, UK. *[email protected]
The AstroChemical Ices Database (ACID) [1] is a unique data repository that contains Vacuum UltraViolet (VUV) and InfraRed (IR) spectra collected from experiments that mimic the icy mantles of the interstellar dust analogs. Spectra presented in the database are from molecules that are already identified in the interstellar medium and potential candidates that await identification. There is a dire need for such spectral studies in order to understand the physico-chemical nature of the molecular ices. In particular, the VUV spectra presented are also of use to compare data from UltraViolet Imaging Spectrograph (UVIS) on board Cassini spacecraft that scans the moons of Saturn.
PRL’s ACID database is now a part of the European database called SSHADE [2] (Solid Spectroscopy Hosting Architecture of Databases and Expertise). Solid Spectroscopy Hosting Architecture of Databases and Expertise (SSHADE) is a multi-database infrastructure in experimental solid spectroscopy for a VESPA sub-network of 21 European contributor groups (8 countries) + 2 non-European (India, Taiwan). It puts online a large set of state of the art spectral data of ices, minerals, organic material and extra-terrestrial materials for the astronomical/astrophysical user community allowing them to interpret observations of planets and small body surfaces, aerosols and grains. This database is useful for analysis, modeling and Interpretation of spectroscopic observations (X-rays to mm) of planetary surfaces & aerosols, inter- & circumstellar grains. The database is hosted by OSUG Data Center in Grenoble, France.
We wish to propose to evolve into a larger database where we aim at creating and unifying the atomic / molecular database containing atomic/molecular data of Indian researchers for its global visibility.
Further, in the Low temperature Astrochemistry laboratory at PRL, we aim to carry out experimental cross sections measurements of some solid/icy molecules, which are of interest in Astrophysical studies. The theoretical cross-sections of the targets will be supplemented by using the well know CSP-ic approach [3].
________________
[1]. https://www.prl.res.in/~dinesh/acid/
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[2]. https://www.sshade.eu [3]. K. N. Joshipura, & N. Mason, Atomic-Molecular Ionization by Electron
Scattering: Theory and Applications, Cambridge University Press, doi:10.1017/9781108551489, (2019).
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Theoretical investigations on electronic structure of 4,4′ dibromobiphenyl, a flame-retardant material
Kiran Kumar Gorai1*, Aparna Shastri1,2, Asim Kumar Das1 and S. N. Jha1,2 1Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085,
India 2 Homi Bhabha National Institute, Anushaktinagar, Mumbai-400 094, India
Polybrominated Biphenyls (PBBs), which belong to a group of halogenated hydrocarbons, formed by replacing one or more hydrogen atoms with bromine atoms on a biphenyl ring, are being widely used in textile and electronic industries as flame-retardants1. They also have been used as additives in plastic. These products, whether in use or waste, leach PBBs into the environment and contaminate the air, soil and water. PBBs have been found in ruminants2, bird eggs3 and reported as carcinogenic4. Hence, it is very essential to understand the chemical reactions involved in all these processes at a microscopic level, which requires detailed information about the ground and excited state electronic structure of the molecules. 4,4′ Dibromobiphenyl (DBBP), a typical example of a PBB, is taken and studied here as no reports on its electronic absorption spectrum are found in the literature to best of our knowledge.
(a) (b)
Figure: (a) Molecular Structure of 4,4′ Dibromobiphenyl (DBBP) (b) simulated stick spectrum of electronic excited states of DBBP.
The geometry optimization and vibrational frequency calculations of neutral and ionized DBBP have been carried out using density functional theory (DFT) for a variety of basis sets and correlation functionals. The optimized geometrical structure of this molecule is shown in Figure (a). The vibrational frequencies for the lowest energy conformer, which is predicted to be of D2 symmetry, have been calculated and compared with NIST data5. Time dependent DFT (TDDFT) calculations have been performed for the analysis of electronic excited states. The simulated stick spectrum is shown in the Figure (b). Our next objective is to record the UV-VUV
P-64 absorption spectrum of DBBP to compare with the theoretically simulated spectrum and work has been initiated in this direction. However, as DBBP is in solid form (white powder) at room temperature with a very low vapor pressure, it is quite challenging to obtain its gas phase absorption spectrum. Details of the theoretical calculations performed and results obtained will be discussed. ______________
[1] R. von der Recke, W. Vetter, J. Chromatogr., A, 1167, 184 (2007). [2] W.H. Gutenmann, D.J. Lisk J. Agric. Food Chem., 23 (5), 1005 (1975). [3] F. Gao, X.J. Luo, Z.F. Yang, X.M. Wang, B.X. Mai Environ. Sci. Technol., 43 (18), 6956 (2009). [4] M. Alonso, S. Casado, C. Miranda, J.V.Tarazona, J.M. Navas, B. Herradón Chem. Res. Toxicol., 21, 643 (2008). [5] NIST Gas-Phase InfraredDatabase (https://webbook.nist.gov/cgi/cbook.cgi?ID=C92864&Mask=80#IR-Spec)
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Interaction potentials and collision cross sections for ultracold 7Li+-7Li ion-atom system
A. Pandey1*, M. Niranjan1, N. Joshi1, S. A. Rangwala1, O. Dulieu2 1 Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore, 560080,
India 2 Laboratoire Aimé Cotton, CNRS/Université Paris-Sud/ENS Cachan, Orsay Cedex, 91400,
France *[email protected]
We have studied scattering processes in the 7Li+-7Li ion-atom system for the temperatures starting from few K to sub-μK. In the presented work, the potential energy curves (PECs), the ground and first excited state of the Li2
+ molecular ion, X2Σg
+ and A2Σu+, which are associated with the ground states of Li+ ion and Li atom in the
asymptotic limit, are considered. These states are computed using the multi-reference configuration interaction method with aug-cc-pCV5z basis sets. Numerical extrapolation of the PECs is performed in the large-R (> 50 ao) and small-R ( < 2 ao) regions. Scattering process in the 7Li+-7Li ion-atom system is described using the partial wave analysis. The PECs are used to determine the low energy scattering phase shifts, which are employed to compute the ion-atom total scattering cross section for the system. The s-wave cross section determined by our calculations for the 7Li+-7Li system is about 7.5*108 a0
2.
P-65 We discuss the contributions arising from the X2Σg
+ and A2Σu+ states for both scenarios
when the identities of the participating entities, Li+ and Li, are retained or interchanged in the collision events. The result suggests that below 10-10 a.u. collision energy, in the energy range where the s-wave collision dominates, occurrence of the scattering events in which the identities of the participating entities get interchanged becomes substantial. We also examine the effects of minor alterations in repulsive wall positions of the calculated PECs on the scattering parameters. We find that the total cross section in the s-wave limit is extremely sensitive to the precision of the PECs, and we discuss the major sources of the observed uncertainties. We also highlight the importance of the features in the total cross section that are arising from the scattering collisions associated with the first few partial waves; these features pick smaller variations with the alterations in the PECs and also appear in the relatively higher temperature regimes. ________________ [1] R. Côté and A. Dalgarno, Physical Review A 62, 012709 (2000) [2] H. Massey, and M. RA Smith, Proc. R. Soc. Lond. A 142, 142 (1933)
P-66
Resonance Revival in Elastic Scattering of H Atom with Variants of C60
Km Akanksha Dubey1*, ShwetaAgrawal2, T. Rajagopala Rao3 and Jobin Jose4
1*Department of Physics (Indian Institute of Technology Patna), Bihta 801103, Patna, India _1
2Department of Chemistry (Indian Institute of Technology Patna), Bihta 801103, Patna, India_2
Fullerenes have become one of the prime attention of the scientific community in various experimental and theoretical investigations, since it was realized experimentally [1]. It has been used in several scattering experiments and many interesting results have been reported [2-3]. In a realistic collision experiment with the C60, the interaction potential due to the fullerene cage can be altered in a variety of ways, such as ionizing the C60 [4], changing the number of C atoms it contains, via charge transfer mechanism etc. In this work, elastic scattering of H atom with variants of C60 is reported. In an earlier study [5], elastic resonant scattering of H-C60was reported with the interaction potential for this system calculatedasa double humped barrier with a maximum near the boundary of C60 shell. This potential is parameterized using a combination of two Gaussian functions. For the present work, variants of C60 have been simulated by varying heights of the Gaussian functions.
Figure 4 and 2: Partial cross section for ℓ=0 with batches 1 and 2 with respect to incident energy (left) and q vs barrier height (right) is plotted.
Heights of the Gaussian functions have been chosen such that a resonance will evolve at least through one wavelength of the glory oscillations in the cross-section.We have studied total and partial (resonant) scattering cross-section, phase shift, and time delay in different batches corresponding to different barrier heights. Resonant width, resonant energy and Fano resonance parameter q[6] with respect to barrier height is also calculated. A very peculiar phenomenon of a sequential and
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gradual evolving of resonances modulated by the glory oscillationsis observed, as shown in Fig. 1. The evolution is so peculiar that the shape of a particular resonance is re-appearing for scattering with variants of C60, which is called as “resonance revival”.To know thoroughly the role of glory oscillations in such revival, deflection function will also be presented. Fig. 2 shows the revival of the resonances in terms of q.
[1] A. R. Kortan, N. Kopylov, S. Glarum et al., Nature355, 529-532 (1992). [2] Markus Arndt, Olaf Nairz, Julian Vos-Andreae et al., Nature 401, 680-682 (1999). [3] S. Bommel, N. Kleppmann, C. Weber et al., N. Comm. 6388, 1-8 (2014) [4] Klavs Hansen, Robert Richter, Michele Alagia et al., Phys. Rev. Lett. 118, 103001-103005 (2017). [5] Km Akanksha Dubey et al.,J. Phys. B: At. Mol. Opt. Phys.52,035203-035214 (2019). [6 ]U.Fano, Phys. Rev. 124, 1866-1878 (1961).
P-67
Analysis of 5s25p4-5s25p35d transitions in seventh spectrum of cerium
Abdul Wajid*; S.jabeen Department of Physics,Aligarh Muslim University Aligarh 20202
The spectrum of six-times ionized Cerium (Ce VII) has been observed with 3-m normal incident vacuum spectrograph in the 300-2000 Å wavelength region with triggered spark source. Only the ground 5s25p4 and the excited 5s5p5, 5p36s, 5s5p5 and 5p35d configurations have been studied so far [1]. In which out of 39 levels of 5p35d only one levels is to be known only. Our aim to this analysis is to establish unknown levels of 5p35d configuration. In order to predict 5p35d levels, the ab-initio pseudo relativistic CI calculations carried out for 5p4, 5p36p, 5p35d, 5p36s and 5s5p5 configurations, with inclusion of interacting configurations using Cowan’s code [2]. In the present analysis we have identified 5s25p4-5s25p35d transitions, which are used to establish new energy levels belonging to 5p45d configuration. ________________ [1] A. Tauheed and Y. N. Joshi, The 5s25p4- (5s5p5 + 5p36s) transitions in Ce VII and 5s25p3 4S – 5s5p4
4P transitions in Ce VIII, Can. J. Phys. 86,713 (2008). [2] R. D. Cowan, The theory of Atomic Structure and Spectra, University California Berkeley, CA, USA, (1981) And Cowan Code Package for windows by A. Kramida. Available at (http://das101.isan.troitsk.ru/cowan)
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Establishment of ground configuration and MCDHF calculations for seven times ionized Cerium: Ce VIII
Abdul Wajid*, S. Jabeen
Department of Phtsics, Aligarh Muslim University, Aligarh 202002 *[email protected]
The cerium spectrum has been photographed on a normal incident spectrograph using spark source, equipped with a grating having the resolution of 1.38 Å/mm in the first order. Resonance lines of Ce VIII have identified with the isoelectronic extrapolation of Sb-like ions. We have established all the ground state energy levels of Ce VIII for the first time. In the excited 5s5p4 configuration out of 3 reported levels, one has been revised and all remaining levels of the 5s5p4 configuration have now been established [1]. The theoretical Energy levels, wavelengths, transition probabilities and lifetimes are calculated, among 11 levels of the 5s25p3 and 5s1p4 configurations for Ce VIII, by adopting GRASP2018 package based on fully relativistic Multi-Configuration Dirac-Hartree-Fock (MCDHF) wave functions [2]. The electron correlation effects, Breit interaction and quantum electrodynamics effects have been considered in the calculation. The experimentally established energy levels are compared with theoretical results. ________________ [1] A. Tauheed and Y. N. Joshi, The 5s25p4- (5s5p5 + 5p36s) transitions in Ce VII and 5s25p3 4S – 5s5p4
4P transitions in Ce VIII, Can. J. Phys. 86,713 (2008). [2] C. Froese Fischer, G. Gaiglas, P. Jönsson and J.Bieroń , Grasp2018 – A fortran 95 version of the General Relativistic Atomic Structure Package, Comput. Phys. Commun. (In Press) (2018).
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The Rydberg and dissociative states of CH: An R-matrix study K.Chakrabarti1, R.Ghosh2* and B.S.Choudhury3
1 Department of Mathematics,Scottish Church College,1&3 Urquhart Sq., Kol-700006,India. 2Department of Mathematics, SukumarSenguptaMahavidyalaya, Keshpur,
PaschimMedinipur,721150,India 3 Department of Mathematics, Indian Institute of Engineering Science and
Technology,Shibpur,Howrah,711103,India *[email protected]
Methylidyne was one of the first molecules to be detected in ISM and is quickly destroyed in ordinary conditions but is abundant in the ISM.Besides, it plays an important role in understanding carbon erosion and redeposition in fusion reactors with graphite as a plasmafacing material [1].To know the chemistry of CH and its ion CH+,it is very important to know the potential energy curves (PECs),resonance positions and widths.The dissociative states of CH play a dominant role for the dissociative recombinationof the CH+ionwhich is responsible for its destruction in the ISM.To the best of our knowledge only one dissociative state of 2Πsymmetry given by Takagi[2] has been known till now.Thismotivates us to investigate and identify other dissociative states of CH. The molecular R-Matrix formalism is used to calculate bound and continuum states of the CH molecule.PECs for the bound states of doublet and quartet symmetry are obtained between 1-9a.u.internuclear distances.Resonance positions and widths for low lying Feshbach resonances are obtained for states with doublet symmetry.Several dissociative states of2Π, 2Σ+ and 2Δsymmetry,that weretill nowunknown,have been found and are expected to be useful for other collisional calculations,in particular for the dissociative recombination of the CH+ ion.
Figure1. PECs of Rydberg states,resonance curves and corresponding widthsof 2Π symmetry as afunction of inter nuclear distance.
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[1] G. A. van Swaaij, K. Bystrov, D. Borodin, A. Kirschner, L. B.van der Vegt, G. J. van Rooij, G. D.Temmerand W. J.Goedheer, Plasma Phys. Control.Fusion54, 095013 (2012). [2] H. Takagi, N. Kosugi, and M. L. Dourneuf, J. Phys. B: At. Mol.Opt. Phys. 24, 711 (1991). [3]K. Chakrabarti, A. Dora, R. Ghosh, B. S. Choudhury, andJ. Tennyson, J. Phys. B: At. Mol. Opt. Phys.50, 175202(2017). [4] L. Carata, A. E. Orel, M. Raoult, I. F. Schneider, and A. SuzorWeiner, Phys. Rev. A 62, 052711 (2000).
P-70
The 5p65d7-5d65f transition array in the fifth spectrum of gold: Au V Aashna Zainab1 and A. Tauheed2*
Physics Department, Aligarh Muslim University, Aligarh-202002 Email: [email protected]*
The third and fourth spectrum of gold has been investigated earlier in our laboratory. Currently, we are working on thespectral investigation of 5p65d7-5d65ftransition array of the fifth spectrum of gold.Au V ion, having 19 energy levels in its ground configuration 5p65d7, has a very complex structure. The two lowest configurations namely 5d66s and 5d66p of this ion have been studied experimentally by Azarov et al [3]. We are investigating atotally new configuration5d65f which alone has346 energy levels and is directly connected to the ground. The transitions of this array lie in grazing incidence region and were recorded on 10.7- m Grazing Incidence spectrograph at NIST laboratory in Washington using triggered spark source.
We are reporting the first experimental information on these transitions using predictions from Cowan’s code [4] based on HF method which includes the superposition of interacting configurations and relativistic corrections. For reliable predictions, we have included all possibly interacting configurations like 5d6ns (n=6-8), 5d6nd (n=6-8), 5d56s2 and 5d56p2 for even parity configurations and 5d6np (n=6-8), 5d6nf (n=5-7), 5d56s6p and 5d46s26p configurations for odd parity matrix. The work is in progress to establish these energy levels experimentally and will determine the energy parameters using least squares fitted parametric theory. The latest results will be presented at the conference.
_______________________________
[1] V. I. Azarov, A. J. J. Raassen, J.-F. Wyart, Y. N. Joshi, and S. S. Churilov, Phys. Scr. 61, 133-141 (2000) [2] Cowan RD. The theory of atomic structure and spectra, Berkeley, CA, USA: University California; 1981. and Cowan Code package for Windows by A. Kramida available from doi:10.18434/T4/1502500 (2018)
P-71
NEW CONFIGURATIONS IN TREBLY IONIZED BISMUTH: Bi IV Kumari Arya. Neelam*, A. Tauheed#
Department of physics, AMU Aligarh-202002. *[email protected] , #[email protected]
The investigation of bismuth spectra have special significance due to various reasons firstly its abundance was observed in some chemically peculiar (CP) HgMn stars x Lupi and HR 777[1] and its high nuclear spin which is responsible for the study of hyperfine structure . We have undertaken the investigation on the fourth spectrum of bismuth (Bi IV) in the vacuum ultraviolet wavelength region (300-2075A). The ground electronic configuration of Bi IV is 5d106s2 which is isoelectronic with Hg I. The spectra of bismuth were recorded on a 3-m normal incidence vacuum spectrograph at Antigonish laboratory (Canada) using a triggered spark light source.
The excited odd parity configurations such as 5d106s (6p, 7p, 5f), 5d96s26p and in even parity system the configurations 5d10 6s (7s, 8s, 6d), 6p2 were reported in the literature though some of them partially. The data is very old and the accuracy of the measured wavelength is poor therefore needed new measurements. In our present study apart from confirmation of earlier work we also have considered the extension of the previous work to include new configurations namely 5d96s6p2 in even parity and 5d10 6p6d, 5d106p7s also 5d96s26p [2] in odd parity system. The theoretical assistance was made by using Cowan’s computer code [3]. Though, some of the levels from these configurations lie above the ionization limit are still unknown. The work is still in progress and the latest findings will be presented at the conference. This will certainly precise the energy parameters and the calculations of other atomic parameters like transition probabilities, wavelength and oscillator strength.
___________________________________________________________________________
[1] Wahlgren G M, Brage. T, Reader.J et.al. The astrophysical Journal, 551, 520-535 (2001). [2] Multiplet and Hyperfine Structure Analysis of Bi IV. Discussions of Perturbation Effects. A.B. Mclay and M.F Crwaford , University of Toronto .The Physical Review , Vol44 December 15,1933. [3] Cowan, R.D. The Theory of Atomic Structure and Spectra; University California Press: Berkeley, CA, USA, 1981. And Cowan code programs.
P-72
M-shell ionisation in Au and Pb: The Molecular Orbital Picture C.V. Ahmad1,2*, R. Gupta1,2, K. Chakraborty1,2, M. Ganguly3, D. Swami4, P. Verma1 1Department of Physics, Kalindi College, University of Delhi, New Delhi 110008
2Department of Physics and Astrophysics, University of Delhi, Delhi 110007 3Department of Physics, Amity Institute of Applied Sciences, Amity University,
Noida 4 Inter University Accelerator Center, New Delhi 110067
The impact of multiply charged high-Z ions on high-Z (Z = atomic number) atoms lead to several fascinating atomic phenomena, paving the way for studying various fundamental interactions. The literature is abound with investigations as well as theoretical description of light ion interactions with various targets [1]. Interestingly, for heavy ion impact at low energy (few 100 keV/u) regime, where collision adiabaticity <<1, available theories fail to provide a satisfactory account of the observed phenomena. In such cases, an alternative approach, namely the molecular orbital model, is used to understand the interaction processes such as shell couplings and vacancy sharing mechanisms. The aim was to investigate quasi-molecular ( <<1) collisions with the aid of molecular orbital model. Beam of Xeq+ ions (q = 12,14 & 17) of energies in the range 3-5 MeV was obtained from the 10 GHz ECR ion source of Low Energy Ion Beam Facility (LEIBF) at Inter University Accelerator Center (IUAC), New Delhi. Thin carbon (20 g/cm2) backed foils of Au and Pb of thickness 500 g/cm2 were kept at the center of experimental chamber inclined at 450 with respect to forward beam direction. The X-Rays emitted during the collision were measured by two silicon drift detectors (FWHM 120 eV at 5.9 keV) mounted at 450 and 900 with respect to the incoming beam. The beam current was monitored by the collection of charge on a Faraday cup placed at beam exit port of experimental chamber. An electron suppressor having an optimized voltage of -300 V was also kept around the collision center to suppress the secondary electrons.
Figure 1. Au X-Ray spectrum recorded for 3 &5 MeV of Xe12+ and Xe17+ ion impact respectively.
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From the resulting X-Ray spectra, it was observed that an increase in the charge state of projectile (12+ to 17+) lead to an increase in intensity of target X-Rays, revalidating the charge state effect observed earlier by different authors [2] as well as indicating an interaction mechanism in addition to the well-known electron capture or coulomb ionisation processes viz. the molecular orbital formation. Similarly, the observed shift in X-Ray diagram lines of the target can be explained in terms of multiple ionisation of target atoms due to high-Z ion impingement. Production and ionization cross-sections have been calculated and compared with direct coulomb ionisation theories to understand the deviations occurring between theoretical assumptions and experimental observations and will be presented in this light.
_____________ M. Pajek, D. Banas, J. Braziewicz, et al., Phys. Rev. A 73, 012709 (2006) and references therein. [2] C. Ying, Y. ShengSheng, Y. ZhiHu, et al., Sci. China Ser G-Phys Mech. Astron 51, 1240 (2008).
P-73
Study Of He- and Li-Like Fe, Ni &V Using Multi Channel Doppler Tuned Spectrometer Setup
Ranjeet K. Karn1* , Deepak Swami2, Janmejay Mahto1, Basu Kumar4 , C P Safvan2 and T Nandi2
1 University Dept. of Physics, Kolhan University, Chaibasa-833201 2Inter University Accelerator Centre, New Delhi - 110067
Precision spectroscopy of highly charged ions provides a powerful tool to study many unexplored realms of physics, shedding light on many astrophysical, quantum electrodynamic, atomic collision and spectroscopic mysteries. Beam-foil spectroscopic technique is one of the most elegant tools to study highly charged ions for the measurement of both transition energies and lifetime. However this technique suffers from inherent cascading and blending problem. If the level under study is repopulated by the decay of higher levels, then this is called cascading effect. Cascading problem is inherent to BFS, and hence independent of detectors spectral resolution. On the other hand the presence of nearby transitions (below the detector resolution i.e. 150 eV at 5.9 keV) in same ion species causes intraion blending, where as similar transitions from neighboring ion species give rise to inter-ion blending also called satellite blending. In contrast to the problem imposed by cascading effect, intra-ion and inter-ion blending effect imposes problem due to experimental limit of detector resolution. To eradicate this problem, we have designed and developed high resolution multichannel Doppler tuned spectrometer (MCDTS) setup coupled with high precision foil movement system at IUAC New Delhi [1].
Figure 1. The Schematic of MCDTS Setup.
P-73 165, 170 and 150 MeV Beam of 56Fe, 58Ni and 51V ions, respectively from the 15 UD Pelletron accelerator at IUAC, New Delhi was used in these experiment. When a well focused beam interacts with thin Carbon foil, various electron stripping and capture process take place, which produce the excited H-, He- and Li-like Fe ions. We have resolved the 1s2s 3S1 - 1s2 1S0 (M1) transition in He-like from its satellite 1s2s2p 4P5/2 - 1s22s 2S1/2 (M2) transition in Li-like with reasonably high precision by using MCDTS setup energetically. Details of experimental setup and result of Fe will be discussed in details along with preliminary result of Ni and V. ________________ [1] Ranjeet K. Karn at al Rev. of Sci. Instrum.85 066110 (2014)
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Quantum Phase Transition in Screened Two-electron System A. Sadhukhan1,2*,S.Dutta3, and J.K. Saha1*
1 Department of Physics, Aliah University, Newtown, Kolkata -700160 2Department of Physics, Adamas Institute of Technology, Barasat, Kolkata-700126
3 BelghariaTexmaco Estate School, Belgharia, Kolkata -700056 *email: [email protected] , [email protected]
The stability of symmetric three-body system under coulomb interaction is a major issue for many branches of physics. Mass and charge of the particles use to play the fundamental role in the stability of the system. During the last few decades the stability of two electron system as a function of Nuclear charge (Z) in its ground state have extensively studied. The critical nuclear charge (Zcr), the minimum amount of nuclear charge required to have at least one bound state for the said system had been predicted with very high precision [1]. The studies on the said system under screened coulomb interaction are also gaining interest due to its relevance in astrophysical and laboratory plasmas [2,3]. It has been found that the bound state of the system undergoes Quantum Phase Transition (QPT) as Z approaches to Zcr[4]. In the present work, the variation of energy of a model two electron system having Nuclear Charge Z, bound via screened coulomb interaction have been studied in its ground state adopting soft wall strategy of stabilization method [5]. The electron-electron correlation has explicitly incorporated in the wave function by considering multi exponent Hylleraas type basis. Zcrhas been predicted for different screening constant (μ) for the given system. Expectation values of different physical quantities have been calculated with 1035 term basis function for Z=1.0 and at the vicinity of Zcr for different μ values. Abrupt change in the expectation values of the structural parameters of the system has been observed in the vicinity of Zcr justifying QPT. To ensure QPT, Two Particle Density (TPD) have been calculated at Z=1.0 and at the predicted Zcr value of the system for different μ vales. In Figure 1 TPD as a function of electronic positons with respect to the nucleus, has been depicted for μ=0.0. Structural symmetry breaking is clearly observed as the evidence of QPT.
(a) (b)
Figure 1. Contour plot of TPD for (a) μ=0.0 and Z=1.0; (b) μ=0.0 and Z=0.91.
P-74 ________________ [1] C. S. Estienne, M. Busuttil, A. Moini, G.W.F. Drake, Phys. Rev. Let. 112, 173001 (2014). [2] S.Dutta, J.K. Saha, S. Bhattacharya, T.K. Mukherjee, Asian J. Phys. 10, 25, (2016). [3] H. E. Montgomery Jr., K. D. Sen, J. Katriel, Phys. Rev. A, 97, 022503 (2018). [4] S. Kais, Q. Shi, Phys. Rev. A, 62, 060502(R), (2000). [5] J.K. Saha, T.K. Mukherjee, Phys. Rev. A, 80, 022513 (2009).
P-75
New Energy levels in the spectrum of singly ionized iodine: I II
A Tauheed and Anjum Naz
Department of Physics, Aligarh Muslim University, Aligarh-202002, India
Abstract:
The spectrum of singly ionized iodine ( I II) with ground configuration 5s25p4 is a four electron system and possess a complex structure. Strong interaction and level mixing among the levels of same parity configurations is expected. A comprehensive report on I II was published [1] about five decades ago but those results are lacking satisfactory theoretical interpretation. Consequently, this spectrum was considered for presentation in this conference with detailed theoretical and experimental support. The experimental recording of iodine spectrum was made on a 3-m normal incidence vacuum spectrograph in the wavelength region 300-2080Å using a triggered spark source. Lithium iodide powder was stuffed into the cavity of aluminium electrodes to excite the spectrum. Higher wavelength data was supplemented from ref [1]. The theoretical calculations were carried out by Cowan’s code involving the configurations 5s25p4, 5s25p3[np(n=6-9) + nf (n=4-9) + nh(n=6-8)] for even parity matrix and 5s5p5 + 5s25p3[ns (n=6-10) + nd(n=5-9) + ng(n=5-8) for odd parity system. Least squares fitted (LSF) parametric calculations were carried out for final interpretation of the results. Several new experimental energy levels have also been found in even parity configurations and the missing level in the odd parity namely 5p35d 3G5 is now located at 102535.3 cm-1.
P-76
Ground state energy levels of two-electron ions confined in harmonic potential environment
A. Hazra* and S. Bhattacharyya Dept. of Physics, Acharya Prafulla Chandra College, New Barrackpore, Kolkata 700131,
India *[email protected]
Quantum mechanical description of two-electron ions is a subject of extensive theoretical interest as it provides a fundamental testing ground for the accuracy of different theoretical calculations. Precise estimates of the energy levels of two-electron atoms are of great importance for astrophysical data analysis, plasma diagnostics ETC. The behaviour of quantum mechanical systems under various external confinements provides useful information about the surroundings. Recent advances in semiconductor technology have allowed the construction of new quantum systems, which are often referred to as artificial atoms or quantum dots. In the present work our aim is to study the variation of energy (for ground state) values in presence of external harmonic potential V(ri) = 1
2Kri
2 .
Figure 1. Variation of ground state energy values of He and He+ in presence of harmonic potential
The energy values of 1s2 (1Se) state of ions having Z = 2 – 6 are estimated for different strengths of harmonic potential by using explicitly correlated wave function in Hylleraas coordinates. The Schrӧdinger equation is solved in the framework of Rayleigh-Ritz variational method. We have also estimated the ground state 1s (2S) energy of hydrogen-like ions having Z = 2 – 6 and hence studied the variation of ionization potential of two-electron ions with respect to the strength of external harmonic potential.
P-77
Higher -component quadrupole polarizabilities of alkaline earth metal ions
Mandeep Kaur*1, Sukhjit Singh1, Bindiya Arora1, B.K. Sahoo2
1Guru Nanak Dev University, Amritsar, Punjab-143005, India 2Physical Research Laboratory, Navrangpura,Ahmedabad-380009, India
In the present work, derivations of the higher tensor components of the quadrupole polarizabilities are given and the static as well as dynamic quadrupole polarizabilities for the metastable states and ground state of the Ca+, Sr+ and Ba+ alkaline earth metal ions are calculated. The scalar and tensor quadrupole polarizabilities are useful to estimate the uncertainties due to the gradient of electric fields in the clock frequencies of Ca+, Sr+ and Ba+ alkaline earth metal ions[1]. Also, we intend to analyse the effect of contribution of quadrupole polarizability on the magic wavelength which is already calculated for these ions using dipole polarizability[2]. Theoretical method used in my work is Relativistic All Order method.
The graph for dynamic quadrupole polarizability for Ba+ ion is given below. Similarly the graphs for other ions are plotted in this work
P-78
Ab initio study of the reaction kinetics of X+O3 → XO+O2 (X=Cl,Br,I)
Gargi Nandi# and Tapas Kr. Ghosh
Department of Physics, Diamond Harbour Women’s University Sarisha, DH Road, South 24-Pgs, West Bengal-743368, India
Halogen atoms play a fundamental role in Ozone depletion particularly in lower stratosphere One halogen atom can destroy up to 100,000 Ozone molecules via the reaction:
X + O3 →XO + O2 (X= Cl, Br, I).
The above mechanism of ozone destruction has been supported by the detection of XO complex in the stratosphere. Ab initio calculations have been done to investigate various minimum energy geometries and transition state geometries of the said key reaction. Geometries and frequencies have been identified at the MP2 level of theory using extensive basis sets. The energetics has been studied at the Configuration Interaction level of theory. Several spectroscopic properties are to be reported.
References:
[1] S. Solomon, R.R. Garcia and A.R. Ravishankara, J. Geophys. Res. 99, 20491 (1994).
[2] D.Y. Hwang and A.M. Mebel, J. Chem. Phys, 109, 10847 (1998). ----------------------------------------
#Presenting Author
E-mail: [email protected] Mobile: 9733420210
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Natural Atomic Charge and Nonlinear Optical Analysis of Some Charge Transfer Complexes between Chloranilic Acid and Different
Donors
Ziya Afroz1,*, Mohd. Faizan2 and Shabbir Ahmad2
1 Department of Chemistry, Aligarh Muslim University, Aligarh, India-202002 2 Department of Physics, Aligarh Muslim University, Aligarh, India-202002
This work is in continuation with our previous investigation [1]. Herein, natural atomic charge analysis of charge transfer (CT) complexes of chloranilic acid with different donors; 1) 4-aminoaniline (4AA), 2) 2-picolonic acid (2PA) and 3) 2-aminopyrimidine (2AP) have been compared with their constituents using DFT/6-311G(d,p) [2]. After that, nonlinear optical (NLO) properties of titled complexes have also been investigated thoroughly using the very level of theory [3].
Figure 1. Depiction of CT complex formation of chloranilic acid with different donors; 1) 4AA, 2) 2PA and 3) 2AP.
________________ [1] Z. Afroz, M. Faizan, S. Ahmad, A. Ahmad, AIP Conf. Proceedings (to be published). [2] Z. Afroz, M. Faizan, M. J. Alam, V. H. N. Rodrigues, S. Ahmad, A. Ahmad, J. Mol. Struct. 1171, 438 (2018). [3] M. Faizan, Z. Afroz, M. J. Alam, V. H. Rodrigues, S. Ahmad, A. Ahmad, J. Mol. Struct. 1177, 229 (2019).
P-80
Electronic structure study of serotonin molecule: A neurotransmitter
Hemlata Bisht1*, Sandeep Pokharia2 and Hirdyesh Mishra1
1Department of Physics MMV, Banaras Hindu University, Varanasi 221005, India 2Department of Chemistry MMV, Banaras Hindu University, Varanasi 221005, India
Abstract:
Serotonin is a very well-known neurotransmitter that modulates neural activity and controls a wide range of neuropsychological processes [1]. It is sometimes called the happy chemical [2], because it contributes to wellbeing and happiness. The molecular structure of serotonin is given in scheme 1. In the present work, we studied the electronic structure of serotonin (5-hydroxytryplamine or 5-HT) with the help of Gaussian 09W and Gauss View 5.0 software package. The structure of the compound is fully optimized in the gas phase by Gaussian 09 software using Density Functional Theory (DFT) with Becke’s three parameter hybrid method with the LYP (Lee-Yang-Parr) correlation functional (B3LYP). The 6-311++G(d,p) Pople’s style, one-electron basis set was utilized for the calculations. After geometry optimization the various global reactivity descriptors and absorption/emission spectra are simulated. The results were then compared with experimental observations. A very good correlation is found between computationally simulated and experimentally observed absorption/emission spectra.
________________ [1] B. C. Swain, P. P. Mishra, H. Mishra, U. Tripathy, J. Photochem. Photobiol. A Chem. 367, 219-225 (2018). [2] M. M. Borah, T. G. Devi, J. Mol. Struct. 1161, 464-476 (2018).
P-81
Structure, Relative stability and Dissociation pathways of Acrylonitrile and Propionitrile
I. Bhattacharyya1, A. Sarkar1, A. Sadhukhan2, S. Bagchi3 and P. K. Mukherjee1
1Dept. of Physics, Acharya Prafulla Chandra College, New Barrackpore, Kol- 700131 2Dept. of Physics, Adamas Institute of Technology, North 24 Parganas, Kol-700126
3Dept. of Basic Engineering Sciences, Netaji Subhash Engineering College, Garia, Kol-700152
During last two decades, there have been rapid developments in the field of silicon chemistry, both from experimental and theoretical aspects. The fractional abundances of silicon bearing neutral molecules with respect to H2 have been predicted. The detection of SiH4, SiN and CH3 in interstellar medium and subsequent detection of CH3CN, CH2CHCN, CH3CH2CN and HC4CN indicate there is a possibility that these molecules react with each other to form HCN, HSiN, CH3SiN and SiH3SiN and their isomers and some other cyanides and silanitrile compounds. In this work we have studied the optimized structure, relative energies of CH3CN (Acetonitrile), CH2CHCN (Acrylonitrile), CH3CH2CN (Propionitrile) and its isomer. The dissociation channels have been studied to predict the most favorable dissociation pathway of such molecule. The same study has been done for CH2CHSiN and CH3CH2SiN and for their isomers also. A comparative study has been done for these cyanide compounds and respective silanitrile compounds. All the calculations have been performed using density functional B3LYP and B3PW91 methods and AB INITIO MP2 and QCISD methods and also in G3 and G3B3 methods. The correlation consistent cc-pVTZ basis set is used for B3LYP, B3PW91 and MP2 methods and 6-311++G(d,p) is used for QCISD method. The change in electronic energy, thermal correction to enthalpy and enthalpy change (∆H298.15 //kcal/mol ) have also been studied for the most favorable channel. The TS structure of CH3CN-CH3NC isomerization has also been studied. In the calculation of dissociation energies in all the methods the fragmented atoms and molecules are in their ground state.
____________________________ [1] A. J. Remijan, J. M. Hollis, F. J. Lovas, D. F. Plusquellic, P.R. Jewell; Astrophys. J., 632, 333-339 (2005) [2] B. Mondal, I. Bhattacharyya, N. C. Bera, A. K. Das; Mol Physics 107, 157-164 (2009)
P-82
The Bound state Solutions of Schrodinger equation: An Explicit Algorithm
Balkrishna Shah* * [email protected]
Department of Physics, Faculty of Science, TheM.S.University of Baroda, Vadodara-390002.
An attempt of solution of Schrodinger equation is the common problem in quantum mechanics. The basics of methodology for the solution of a particle under potential V(x) are discussed. The systematic development of an algorithm for evaluation of wave function and eventually eigenvalue including verifying the cut-off boundary in classical forbidden region, forward and backward integration using Numerov algorithm as well as matching of the wave function is performed in FORTRAN 95. In addition graphs are generated to monitor the output at the same time through GNU plot. The evolution of solution is depicted schematically step by step in this work. The present work is unique blend of the Numerov method, root finding scheme of eigenvalue, FORTRAN file handling and Gnu-plot together, where each stage is analysed by the graphical representation. The explicit algorithm can be extended to scattering phenomenon also.
[1] An Introduction to Computational Physics 2nd edition by Tao Pang (Pub.Cambridge University Press) [2] B. Shah International Journal of Advances in Applied mathematics and Mechanics Vol. 2 (2) 2014. [3] D.G.Kanhere, Physics through computation-II, IAPT Physics Education (April 2007) 55-60. [4] P.C.Chow, American Journal of Physics, Computer solution to Schrödinger equation, 40, (1972) 730.
P-83
RaH as a promising candidate for P, T violation experiments N. M. Fazil 1, V. S. Prasanna 2, K. V. P. Latha 1*, M. Abe 3 and B. P. Das 4 1 Department of Physics, Pondicherry University, R. V. Nagar, Kalapet -14, India
2 Physical Research Laboratory, Navrangapura, Ahmedabad-380009, India 3 Tokyo Metropolitan University, 1-1, Minami-Osawa, Hachioji-city, Tokyo 192-0397, Japan
4 Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan *[email protected]
Single valence polar molecules are the current focus in the field of search for signatures of parity (P) and time-reversal (T) violations and physics beyond the Standard Model (SM). Among the proposed candidates, hydride derivatives like HgH [1] have a promising future owing to their magnitudes of effective electric field [2] (Eeff) and scalar-pseudo scalar (S-PS) interaction coefficient [3] (Ws). While the Eeff is useful in determining the electron electric dipole moment, the Ws is required to extract the S-PS interaction coupling constant. In general, the small permanent dipole moment (PDM) and large rotational constant of most of the hydride systems limit their suitability for conventional experiments in this field. We perform a relativistic coupled cluster singles and doubles [2] (RCCSD) calculation at triple zeta basis set level for RaH molecule. The minimum of potential energy curve determines its bond length and occurs at 2.43 Å. In the present work, we determine the Eeff, Ws and PDM to be 81.86 GV/cm, 221.09 kHz and 4.29 Debye respectively. The exceptionally large value of PDM compensates for the high value of the rotational constant and leads to a reasonable polarizing field (~ 80 kV/cm) that can be achieved in an electron electric dipole moment experiment, making RaH molecule the only hydride system to date, that possesses large Eeff and a viable polarizing field. In addition, we have also identified the individual contributions from the electron-correlation terms. The highest contribution is due to the term: XT1 (T1 is the correlated cluster operator) which contains a class of effects called Brueckner pair correlation effects. The correlation corrections for the calculated properties are 16% for PDM and 31% for Eeff and Ws. The high magnitudes of the correlation contributions emphasize the need of RCCSD procedure for probing the underlying many-body effects that collectively result in a certain magnitude of the properties of interest. Apart from the above theoretical perspective, there is also a possibility of laser cooling RaH as it belongs to the alkaline earth metal hydride group [4], which adds to the various other advantages. We hence propose RaH as a potential candidate for investigations to probe new physics searches beyond the SM. ________________ [1] Sudip Samsal, Himadri Pathak, M. K. Nayak, Nayana Vaval, and Sourav Pal, JCP 144, 124307 (2016) [2] M. Abe, G. Gopakumar, M. Hada, B. P Das, H. Tatewaki and D. Mukherjee, Phys. Rev. A 90,022501 (2014). [3] A. Sunaga, M. Abe, M. Hada, and B. P. Das, Phys. Rev.A 93, 042507 (2016). [4] Y. Gao and T. Gao, Phys. Rev.A 90, 052506 (2014).
