02/,0 :* 0HHWLQJ %RRN RI $EVWUDFWV %RRN RI $EVWUDFWV · 02/,0 :* 0HHWLQJ %RRN RI $EVWUDFWV %RRN RI $EVWUDFWV ... wr

MOLIM WG1 Meeting Book of Abstracts 24/09/2018 - 26/09/2018

1

Book of Abstracts

Intra- and inter-molecular (atomic) interactions

(a MOLIM Working Group 1 meeting)

24/09/2018 – 26/09/2018


2

Contents

CONFERENCE SCHEDULE ........................................................................ 2

SESSION A ...................................................................................................... 6

SESSION B ..................................................................................................... 12

SESSION C ..................................................................................................... 18

SESSION D ..................................................................................................... 24

SESSION E ..................................................................................................... 26

POSTERS ....................................................................................................... 30

Additional information at:

https://www.ki.ku.dk/Forskning/fyschem/kjaergaard-group/molim-wg1-meeting/

Conference Schedule

Sunday, September 23 15.00 Rooms available

17.00-19.00

Conference registration


3

Monday, September 24 8.15-8.30

Welcome Henrik G. Kjaergaard (University of Copenhagen)

Session A // Theory - Chair: Ove Christiansen

8.30-9.00

Talk A.1 Attila Császár (Eötvös University)

Ideal Ideal-Gas Thermochemical Functions for Ordinary and Heavy Water

9.00-9.30

Talk A.2 Magnus Gustafsson (Luleå University of Technology)

Methods for calculations of radiative association rate constants: the influence of local thermal equilibrium on the resonance contribution

9.30-10.00

Talk A.3 Roberto Marquardt (Université de Strasbourg )

Time Dependent Quantum Dynamics of the Diffusion of Adsorbates

10.00-10.30

Coffee break

10.30-11.00

Talk A.4 Klaus B. Møller (Technical University of Denmark)

Filming of bond formation and accompanying dynamics in the surroundings

11.00-11.30

Talk A.5 Sonia Coriani (Technical University of Denmark)

Coupled cluster methods for local and ultrafast spectroscopies

11.30-12.00

Talk A.6 Matyas Papai (Technical University of Denmark)

Simulation of Ultrafast Excited-State Relaxation Processes in Functional Transition Metal Complexes by Quantum Wavepacket Dynamics

12.00-13.00

Lunch

Session B // Spectroscopy - Chair: Henrik Kjaergaard

13.00-13.30

Talk B.1 Steen B. Nielsen (Aarhus University)

Optical spectroscopy of rhodamine homodimer dications in vacuo reveals strong dye-dye interactions

13.30-14.00

Talk B.2 Andreas Barth (Stockholm University)

Amyloid β-peptides 1-40 and 1-42 form oligomers with mixed β-sheets according to experimental and computational isotope-edited infrared spectroscopy

14.00-14.30

Talk B.3 Lauri Halonen (University of Helsinki)

Infrared spectroscopy with optical frequency combs

14.30-15.30

Coffee break

15.30-16.00

Talk B.4 Rui Fausto (University of Coimbra)

A Magic Wand for Controlling Molecular Structure

16.00-16.30

Talk B.5 Katharina Meyer (Georg-August-Universität Göttingen)

The Social Life of Carboxylic Acids under Vibrational Scrutiny: From Singles to Pairs and Beyond

16.30-17.00

Talk B.6 Anne S. Hansen (University of Copenhagen)

Vibrational spectroscopy: combing experiment and theory to determine the Gibbs energy of complex formation.

19.00 Dinner at Danhostel


4

Tuesday, September 25

Session C // Theory of Vibrational Motion - Chair: Attila Császár 8.30-9.00

Talk C.1 Stephan Sauer (University of Copenhagen)

Vibrational averaging of NMR and ESR properties with VPT2: how far have we come?

9.00-9.30

Talk C.2 Maria Luisa Senent (IEM-CSIC)

Weak intramolecular interaction effects on the structure and fir spectra of molecules with various torsional motions: ethylene glycol and its isotopologues

9.30-10.00

Talk C.3 Philippe Carbonniere (Université de Pau et des Pays de l’Adour)

Vibrational computations beyond the harmonic approximation: from molecules to periodic systems

10.00-10.30

Coffee break

10.30-11.00

Talk C.4 Emil Vogt (University of Copenhagen)

Absolute Vibrational Transition Intensities of Bimolecular Complexes

11.00-11.30

Talk C.5 Sebastian Erfort (Universität Stuttgart)

Ab initio calculations for a methylfluoride-argon clusters and CH3+-Rg (Rg=He, Ne, Ar) clusters

11.30-12.00

Talk C.6 Emil Lund Klinting (Aarhus University)

An adapted density-guided approach to potential energy surface construction using specialized vibrational coordinates and general fit-basis functions

12.00-13.00

Lunch

13.00-14.00

Poster session

14.00-16.30

Excursion to Rundetårn - The original Observatory for the University of Copenhagen

17.00-18.00

Refreshments in Munkekælderen

19.30 Conference Dinner at Danhostel


5

Wednesday, September 26

Session D // Experimental Methods - Chair: Lauri Halonen 8.30-9.00

Talk D.1 Klaus Müller-Dethlefs (University of Manchester)

An ultra-cold quantum degenerate plasma: Observation of a periodic many-body system

9.00-9.30

Talk D.2 Juha Toivonen (Tampere)

Molecular dynamics by collinear photofragmentation and atomic absorption spectroscopy

9.30-10.00

Coffee break

Session E // Theory - Chair: Jens Wallberg

10.00-10.30

Talk E.1 Niels Engholm (Technical University of Denmark)

Laser-induced Quantum Control of Molecular Processes

10.30-11.00

Talk E.2 David Lauvergnat (Université Paris-Sud)

Smolyak scheme and on-the-fly kinetic energy operator, an efficient combination: application to malonaldehyde in 21D.

11.00-11.30

Talk E.3 Gunnar Nyman (University of Gothenburg)

On the gas-phase formation of the HCO radical: accurate quantum study of the H+CO radiative association

11.30-12.00

Talk E.4 Ove Christiansen (Aarhus University)

Anharmonic Wavefunctions and Franck-Condon factors

12.00-12.15

Closing Henrik Kjaergaard ()

12.15-13.15

Lunch


6

Ideal Ideal-Gas Thermochemical Functions for Ordinary and Heavy Water Attila G. Császár1,2

1MTA-ELTE Complex Chemical Systems Research Group and 2Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary

E-mail: [email protected]

Due to their considerable scientific and engineering interest, temperature-dependent (in the wide range of 0–6000 K) thermochemical properties of molecular systems form part of several information systems. The ideal-gas partition function is assumed to be the product of the internal and the translational partition functions.

For semirigid molecules, the simplest analytic technique to obtain internal partition functions, namely use of the harmonic oscillator and rigid rotor approximations for the vibrational and the rotational motions, respectively, yields reasonably accurate results at relatively low temperatures (especially around room temperature). Partition functions have an integrative nature: they are a direct sum of weighted energy levels. This provides much room for approximate treatments. To obtain highly accurate, high-temperature thermodynamic functions for the water isotopologues requires the use of sophisticated variational nuclear-motion techniques for the computation of the rovibronic energy levels not known experimentally. These techniques have become available in the fourth age of quantum chemistry.

Due to the Boltzmann distribution characterizing thermodynamic equilibria, the contribution of energy levels to the partition function depends strongly on the thermodynamic temperature T of the system. At the lowest temperatures, where the thermochemical functions depend only on a relatively small number of energy levels, an accuracy considerably higher than that provided by even the most sophisticated modeling studies can be achieved, once energy levels of experimental quality are used. The experimental energy levels can be obtained via the MARVEL (Measured Active Rotational-Vibrational Energy Levels) technique utilizing the theory of spectroscopic networks. At the lowest temperatures, one must also pay attention how the ortho and para nuclear-spin isomers of water are treated. It is best to treat these isomers explicitly. Beyond a given temperature, dependent upon the first dissociation threshold of the molecule, unbound states make a significant contribution to thermochemical quantities.

The most accurate and most complete dataset of bound rovibrational energy levels of the ground electronic state of H2

16O can be obtained by combining the complete set of variationally computed levels, employing a highly accurate, empirically adjusted potential energy surface (PES), like the PoKaZaTeL PES of H2

16O, with the accurate MARVEL set of empirical levels. Therefore, we replaced the PoKaZaTeL energy levels with MARVEL energies whenever possible and in this way we obtain a hybrid dataset. A similar replacement was done for the case of heavy water.

For quantification of the uncertainties of the computed thermochemical quantities, it is essential that each energy level has its own uncertainty. The MARVEL energy levels have well determined uncertainties, originating from the uncertainties of the measured transitions. The computed PoKaZaTeL list does not have uncertainties but approximate uncertainties can be chosen: up to 20,000 cm-1 a value of 0.2 cm-1, while above 0.5 cm-1 or even larger, with small effect on the uncertainties of the thermochemical functions.

There are four sources of error preventing the determination of “exact” temperature-dependent internal partition functions, Qint(T): uncertainty about the energy level density, uncertainty of the energy levels, role of unbound (and scattering) states, and uncertainty of the physical constants entering the relevant thermochemical equations.

The data obtained for ordinary and heavy water, with the associated uncertainties, are the most accurate ideal-gas thermochemical data available for H2

16O and the deuterated analogs and heavy water.

Session A

(8:30-9:00)


7

Methods for calculations of radiative association rate constants: the influence of local thermal equilibrium on the resonance contribution

Magnus Gustafsson1, Robert C. Forrey2

1Applied Physics, Luleå University of Technology, Sweden

2Department of Physics, Pennsylvania State University, Reading, USA

Radiative association contributes to molecule production in dust-poor regions of interstellar clouds [1]. The process, whereby two colliding fragments associate through emission of a photon, can be direct or resonance mediated. The latter happens when the potential energy surface has a barrier (e.g. centrifugal) and thereby supports quasibound states. Breit-Wigner theory is typically used to compute the resonant contribution the rate constant. The quasibound states are assumed to be populated through tunneling from the continuum [2]. This method combined with a semiclassical treatment for the direct process gives the result labeled SC+BW in Fig. 1 for the formation of CN molecules. Recently, this scheme has been contested since the quasibound states could also be thermally populated under appropriate environmental conditions [3,4]. The results labeled LTE (local thermal equilibrium) and NLTE-ZDL (non-LTE zero-density-limit) in Fig. 1 correspond to the new scheme, put forward in Ref. [3], and a version of the conventional scheme, respectively. In this work we further illuminate the difference in physics between the two ways to account for resonant radiative association. We show that the simplified semiclassical (simplified SC in Fig. 1) method [5,6,7] is a classical equivalent of the LTE scheme in Ref. [3]. Furthermore, the Breit-Wigner method can also be reformulated to yet one more equivalent of LTE (SC+BW(no rad broad) in Fig. 1). We will elaborate on consequences of these observations.

Fig. 1. Rate constant for formation of CN through AX radiative association.

[1] J. F. Babb and K. P. Kirby, in The Molecular Astrophysics of Stars and Galaxies, edited by T. W. Hartquist and D. A. Williams (Clarendon Press, Oxford, 1998), pp. 11–34. [2] O. J. Bennett, et al., Mon. Not. R. Astron. Soc. 341, 361 (2003); Erratum, 384, 1743 (2008). [3] R. C. Forrey, J. Chem. Phys. 143, 024101 (2015). [4] R. C. Forrey et al., Mon. Not. R. Astron. Soc. 479, 4727 (2018). [5] H. A. Kramers and D. ter Haar, Bull. Astro. Inst. Netherlands 10, 137 (1946). [6] P. S. Julienne, J. Chem. Phys. 68, 32 (1978). [7] M. Gustafsson et al., J. Chem. Phys. 140, 184301 (2014).

Session A

(9:00-9:30)


8

Time Dependent Quantum Dynamics of the Diffusion of Adsorbates Roberto Marquardt

Laboratoire de Chimie Quantique - Institut de Chimie UMR 7177 CNRS/Université de Strasbourg - 1, rue Blaise Pascal - BP 296/R8 - 67008 STRASBOURG CEDEX – France

A time independent quantum dynamical formulation of the dynamical structure factor (DSF) related to particle scattering at mobile adsorbates exist in the case when the adsobates’ excited states have finite lifetimes due to relaxation phenomena [1]. The formula is evaluated quantum mechanically using wavefunctions, energies and lifetimes of vibrational states obtained for H/Pd(111) from first principle calculations. The results are capable of capturing qualitative features of diffusion rates measured by 3He Spin echo experiments [2]. In the present talk, I present results on the diffusion of CO on a Cu(100) surface [3] and discuss a time dependent formulation which will directly link the motion of wave packets and the intermediate scattering function (ISF). [1] T. Firmino, R. Marquardt, F. Gatti, W. Dong, J. Phys. Chem. Lett. 5 4270-4274 (2014). [2] A. P. Jardine, G. Alexandrowicz, H. Hedgeland, W. Allison, J. Ellis, Phys. Chem. Chem. Phys. 11 3355-3374 (2009). [3] D. Zanuttini, F. Gatti, and R. Marquardt, Chem. Phys., 509, 3 (2018).

Session A

(9:30-10:00)


9

Filming of bond formation and accompanying dynamics in the surroundings Asmus O. Dohn,1,2 Gianluca Levi,1,2 Niels E. Henriksen,1 Klaus B. Møller1

1Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark

2Present adress: Faculty of Physical Sciences, University of Iceland, 107 Reykjavik, Iceland

Fundamental understanding of the ultrafast events accompanying photochemical bond formation in a dissipative environment and their impact on catalytic activity has undergone significant advancements thanks to time-resolved studies on binuclear complexes of d8 transition metals. Modern femtosecond X-ray techniques are particularly suited for such investigations. Yet the analysis and interpretation of the experimental outcomes necessitate support from detailed atomistic simulations. Our implementation of QM/MM Born-Oppenheimer Molecular Dynamics (BOMD) in the GPAW DFT code [1,2] meets this demand by delivering accurate information on structural dynamics in solution at a modest computational cost. The present contribution will show how the method was used to assist X-ray free electron laser (XFEL) scattering measurements of [Ir2(Dimen)4]2+ [2,3] and [Pt2(P2O5H2)4]4− [4,5] in order to gain mechanistic insights into excited-state bond formation and accompanying solvent-influenced vibrational relaxation.

[1] A.O. Dohn et al. J. Chem. Theory Comput. 2017, 13, 6010. [2] A.O. Dohn et al., J. Phys. Chem. Lett. 2014, 5, 2414. [3] T.B. van Driel et al., Nat. Commun. 2016, 7, 13678. [4] G. Levi et al., J. Phys. Chem. C 2018, 122, 7100. [5] E. Biasin et al., J. Synchrotron Radiat. 2018, 25, 306.

Session A

(10:30-11:00)


10

Coupled cluster methods for local and ultrafast spectroscopies

Marta Lopez Vidal, Rasmus Faber and Sonia Coriani

1DTU Chemistry, Technical University of Denmark, 2800 Kongens Lyngby, Denmark

Recent advances in synchrotron, laser and detection technology have greatly expanded our ability to investigate matter and obtain insight on its fundamental properties and the processes it may undergo. Technological developments in X-ray free electron lasers (XFEL), for instance, have opened an extraordinary window for imaging individual events in chemical reactions with sub-femtosecond time resolution by using time resolved X-ray near edge absorption spectroscopy (TR-NEXAFS) to get closer to 'seeing' chemical reactions on femto-second or shorter timescales. To exploit the full potential of such advances, accurate theoretical tools are needed. Some of our more recent efforts in the development of highly reliable quantum chemical methods and computational tools to model (time-resolved) core-level spectroscopies will be discussed [1-5]. [1] S. Coriani and H. Koch, J. Chem. Phys. 143 (2015) 181103. [2] R. Faber and S. Coriani, submitted to J. Chem. Theory Comput. [3] M. Lopez Vidal, X. Feng, E. Epifanovsky, A. I. Krylov, and S. Coriani, submitted to J. Chem. Theory Comput. [4] T. J. A. Wolf, R. H. Myhre, J. P. Cryan, S. Coriani, R. J. Squibb, A. Battistoni, N. Berrah, C.Bostedt, P. Bucksbaum, G. Coslovich, R. Feifel, K. J. Ganey, J. Grilj, T. J. Martinez, S. Miyabe,S. P. Moeller, M. Mucke, A. Natan, R. Obaid, T. Osipov, O. Plekan, S. Wang, H. Koch and M. Guhr, Nature Communications 8, 2017 [5] R.H. Myhre, T.J.A. Wolf, L. Cheng, S. Nandi, S. Coriani, M. Guhr and H. Koch, J. Chem. Phys. 148 (2018) 064106.

Session A

(11:00-11:30)


11

Simulation of Ultrafast Excited-State Relaxation Processes in Functional Transition Metal Complexes by Quantum Wavepacket Dynamics

M. Pápai1,2, M. Abedi1, M. Simmermacher1, G. Levi1,

G. Vankó2, T. Rozgonyi2,3, T. J. Penfold4, K. B. Møller1 1

Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark

2 Wigner Research Centre for Physics, Hungarian Academy of Sciences,

P.O. Box 49, H-1525 Budapest, Hungary 3

Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, P.O. Box 286, H-1519 Budapest, Hungary

4 School of Chemistry, Newcastle University,

Newcastle upon Tyne, NE1 7RU, United Kingdom

Understanding, and subsequently being able to manipulate, the excited-state decay pathways of functional transition metal complexes is of utmost importance in order to solve grand challenges in solar energy conversion and data storage. Herein, we present quantum wavepacket dynamics studies on a series of Fe(II)-N-heterocyclic carbene complexes, a novel class of high-efficiency photosensitizers. The presented theoretical investigations lead to a detailed understanding of the effect of ligand substitution on the photorelaxation mechanism [1,2], as well as address methodological aspects of quantum dynamics, such as the correct description of excitation into electronically degenerate states [3] and solvent effects in excited-state simulations [4]. These results, alongside with the related ultrafast spectroscopic and scattering experiments, will contribute to the improved design of novel high-efficiency transition-metal-based functional molecules.

Figure 1: Graphical illustration of wavepacket dynamics in excited triplet metal-to-ligand charge transfer (3MLCT) and metal-centered (3MC) states. ν6 and ν11 denote the nuclear (vibrational) degrees of freedom dominant for the excited-state dynamics; nuclear displacements are given in dimensionless mass-frequecny weighted normal coordinates. [1] M. Pápai, G. Vankó, T. Rozgonyi, T. J. Penfold, J. Phys. Chem. Lett., 2016, 7, 2009–2014. [2] M. Pápai, T. J. Penfold, K. B. Møller, J. Phys. Chem C, 2016, 120, 17234–17241. [3] M. Pápai, M. Simmermacher, T. J. Penfold, K. B. Møller, T. Rozgonyi, J. Chem. Theory Comput. 2018, 14, 3967–3974. [4] M. Pápai, M. Abedi, G. Levi, T. J. Penfold, K. B. Møller, In preparation.

Session A

(11:30-12:00)


12

Optical spectroscopy of rhodamine homodimer dications in vacuo reveals strong dye-dye interactions

Steen Brøndsted Nielsen1

1Department of Physics and Astronomy, Aarhus University

Being alone or together makes a difference for the photophysics of dyes but for ionic dyes it is difficult

to quantify the interactions due to solvent screening and nearby counter ions. Gas-phase experiments

are desirable and now possible based on recent developments in mass spectrometry. Here we present

results on tailor-made rhodamine homodimers where two dye cations are separated by methylene

linkers, (CH2)n. In solution the fluorescence is almost identical to that from the monomer whereas the

emission from bare cations redshifts with decreasing n. Indeed, in absence of screening, the electric

field from one charge is strong enough to polarize the other dye, not only in the excited state but also

in the ground state. An electrostatic model based on symmetric dye responses (equal induced-dipole

moments) captures the underlying physics and demonstrates significant interactions even at large

distances. Such Stark effects could have implications for distance measurements in gas-phase FRET

experiments.

Session B

(13:00-13:30)


13

Amyloid β-peptides 1-40 and 1-42 form oligomers with mixed β-sheets according to experimental and computational isotope-edited infrared spectroscopy

Barth, Andreas1, Baldassarre, Maurizio1, Baronio, Cesare M.1

1Department of Biochemistry and Biophysics, Stockholm University, Sweden

Background: Two main amyloid-β peptides of different lengths (Aβ40 and Aβ42) are involved in Alzheimer's disease. Their relative abundance is decisive for the severity of the disease and mixed oligomers may contribute to the toxic species. However, little is known about the extent of mixing in oligomers. Other proteins have also been suspected to co-aggregate with Aβ. Questions addressed: Do Aβ40 and Aβ42 form mixed oligomers? Methods: We used Fourier transform infrared spectroscopy in combination with 13C-labeling and spectrum calculation to study whether Aβ40 and Aβ42 co-aggregate. Mixtures of monomeric labelled Aβ40 and unlabelled Aβ42 (and vice versa) were co-incubated for approximately 20 min and their infrared spectra recorded. The amide I spectra of labelled, unlabelled and mixed β-sheets were calculated with a self-developed Matlab program. Results and discussion: The spectra of the 1:1 mixtures were different from the average spectra of the labelled and unlabelled peptides, indicating that the vibrational coupling between amide oscillators was affected by mixing. The position of the main 13C-amide I' band shifted to higher wavenumbers with increasing admixture of 12C-peptide due to the presence of 12C-amides in the vicinity of 13C-amides. The effect could be reproduced in spectrum calculations [1]. The experimental results indicate a largely random distribution of Aβ40 and Aβ42 in the β-sheets of the mixed aggregates. Spectrum calculations are consistent with structural models in which each peptide contributes at least two adjacent β-strands (hairpin) to the β-sheets of the oligomers. Conclusions: This work highlights the relevance of heterogeneous aggregates for Alzheimer's and other neurodegenerative diseases. [1] Baldassarre M, Baronio CM, Morozova-Roche LA, Barth A: Amyloid ß-peptides 1-40 and 1-42 form oligomers with mixed ß-sheets. Chem. Sci. 2017, 8: 8247-8254, DOI: 10.1039/C7SC01743J

Session B

(13:30-14:00)


14

Infrared spectroscopy with optical frequency combs

Lauri Halonen, Juho Karhu, Markku Vainio, Markus Metsälä

Department of Chemistry, University of Helsinki, Helsinki, Finland Optical frequency combs (OFC) can be used as accurate optical frequency references, which makes them valuable tools in spectroscopy and kinetics, when applied to various molecular species. A laser source locked to an OFC reference has a stable and accurately known wavelength, which is advantageous in applications that require high resolution, such as sub-Doppler spectroscopy. For spectroscopy, an important prospect is the extension of the OFC technologies from the near infrared into the mid-infrared wavelength region, where the strong fundamental vibrational transitions are found [1]. We have produced a fully-stabilized mid-infrared OFC using a synchronously pumped degenerate femtosecond optical parametric oscillator (fs-OPO) [2]. This comb serves as a direct frequency reference for the stabilization of the idler wavelength of a continuous-wave optical parametric oscillator (CW-OPO), which was used as a light source in molecular laser spectroscopy. We have utilized the OFC stabilized CW-OPO in two sub-Doppler spectroscopy experiments with the resolution and accuracy below 1 MHz in a double resonance two-photon vibrational spectroscopy setup [3]. The CW-OPO pumps a strong mid-infrared transition of acetylene, and a second transition, from the pumped state to an infrared-inactive vibrational state, is recorded with an external-cavity diode laser (ECDL). The ECDL is itself stabilized to the near-infrared OFC that also pumps the fs-OPO. With a free-running CW-OPO, the time available for the measurement of the spectrum is limited to a few seconds, since the CW-OPO long-term frequency drifts are larger than the linewidth of the two-photon transition. With the stabilized CW-OPO and ECDL, we could resolve the shape of the narrow, sub-Doppler transition line with high resolution and a high signal-to-noise ratio (Fig. 1). To counter the typical CRDS limitation of the empty cavity decay rate drift, we have also realized a setup, where the CW-OPO is turned off during a cavity ring-down decay. This allows measuring the two-photon loss and the empty cavity decay rate from a single decay, giving the same advantage as measuring separate off-resonance decays, but the original speed is retained, which is beneficial in two-photon spectroscopy. We have also used a high power mid-infrared singly resonant femtosecond OPO, pumped with a near-infrared optical frequency comb, as the light source for Fourier transform infrared spectroscopy. Cantilever enhanced photoacoustic detection together with the high power spectral density of the light source allows sensitive broadband spectroscopy of trace gasses even with a small sample volume.

Fig. 1 Two-photon absorption spectrum of acetylene transition R(17) of the band ν1 + 2ν3 ← ν3. The spectrum is measured with cavity ring-down spectroscopy when the stabilized CW-OPO idler beam pumps the J=17 rovibrational state of ν3.

[1] M. Vainio, L. Halonen, Physical Chemistry Chemical Physics 2016, 18, 4266. [2] M. Vainio, J. Karhu, Optics Express 2017, 25, 4190. [3] J. Karhu, M. Vainio, M. Metsälä, L. Halonen, Optics Express 2017, 25, 4688.

Session B

(14:00-14:30)


15

A Magic Wand for Controlling Molecular Structure

Rui Fausto

CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.

Properties of isolated molecules and of complex molecular systems are ultimately determined by the shape of the molecules. For many molecules, besides the low-energy conformers that are easily accessible to experiment, high-energy forms exist whose population is negligible (or are not populated at all) in most of the usual experimental conditions. Nevertheless, these higher energy forms very often play important roles under certain specific conditions. In addition, they may have special structural features that make them the most appropriate agents to perform a given role in chemistry, physics or biochemistry/biology. Till very recently, the identification and characterization of high-energy conformers was done only theoretically. Using a simple analogy, the exploration of the molecular conformational landscapes was confined to the “Lowlands”, while the “Highlands” were terra incognita, whose inhabitants were never seen.

The recent development of experimental techniques based on the selective in situ generation of high-energy conformers, by selective vibrational excitation (using near-infrared light) of the easily accessible lower-energy conformers, opened a way for journeying to the molecular conformational highlands. These expeditions have allowed observation of a plethora of novel molecular structures, some of them exhibiting rather unusual properties. Light appears here as a magic wand which can be used to control, in a very specific way, the structure (shape) of the molecules. In this talk, the attendees will be invited to make an excursion on molecular landscapes, learn how the expedition can be prepared, enjoy the contact with the “highlanders” and see how they behave. Several molecular systems will be addressed, ranging from simple molecules exhibiting only two conformers to complex multi-dimensional conformational systems that embrace a larger number of conformers. Acknowledgements: Present and past members of the Laboratory for Molecular Cryospectroscopy and Biospectroscopy, Coimbra, Portugal, and research partners from other laboratories, who have contributed to the studies addressed in this talk, are acknowledged. I thank also the Portuguese Science Foundation (FCT) for financial support (Project PTDC/QEQ-QFI/3284/2014 – POCI-01-0145-FEDER-016617, also funded by FEDER/COMPETE 2020-UE). The Coimbra Chemistry Centre (CQC) is supported by FCT, through the project UI0313/QUI/2013, also co-funded by FEDER/COMPETE 2020-EU.

Session B

(15:30-16:00)


16

The Social Life of Carboxylic Acids under Vibrational Scrutiny: From Singles to Pairs and Beyond

Katharina A. E. Meyer1, Martin A. Suhm1

1 Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Tammannstr. 6, 37077 Göttingen, Germany

Carboxylic acid monomers exist in two forms – the cis- and the trans-rotamer (Figure 1), whereby the cis-form is higher in energy. In cryogenic matrices the cis-monomer has been observed after vibrational excitation of the trans-form [1-5]. In the gas phase, however, no vibrational evidence has been reported yet. An approach to detect the cis-rotamer in a perturbation-free environment with vibrational spectroscopy is to employ a heatable nozzle combined with a supersonic expansion, resulting in the first Raman jet spectrum of cis-formic acid. [6]

Figure 1: Trans- (F) and cis-rotamers (cF) of formic acid.

Unlike for microwave spectroscopy that relies on a permanent dipole moment, the main focus of vibrational spectroscopy of carboxylic acid dimers has been on the inversion-symmetric homo dimers. By extending that focus to the hetero dimers of three carboxylic acids (formic, acetic, and pivalic acid), the exciton splitting of the C=O stretching vibrations as well as the spectral downshift compared to the averaged monomer band position can be analysed for the six homo and hetero dimers. Both values can be exploited as experimental benchmarking data to assess the quality of predictions from quantum chemistry, as any systematic monomer error cancels for the splittings, whereas it is included in the shifts. [6] Another technique that can be very useful to study carboxylic acid aggregation is FTIR imaging, where the space-resolved FTIR spectra are recorded synchronously using a 64 x 64 pixel Mercury Cadmium Telluride (MCT) focal plane array (FPA) detector. The spatial resolution allows for a more dynamic point of view on the aggregation behaviour, as it reveals areas of cluster stability as well as instability in supersonic jets and as such, gives a kinetic perspective that can be very useful in band assignment of transient species such as the formic acid trimer. [7] [1] M. Pettersson, J. Lundell, L. Khriachtchev, and M. Räsänen, J. Am. Chem. Soc. 119, 11715 (1997). [2] M. Pettersson, E. M. S. Maçôas, L. Khriachtchev, J. Lundell, R. Fausto, and M. Räsänen, J. Chem. Phys. 117, 9095 (2002). [3] E. M. S. Maçôas, L. Khriachtchev, M. Pettersson, R. Fausto, and M. Räsänen, J. Am. Chem. Soc. 125, 16188 (2003). [4] E. M. S. Maçôas, L. Khriachtchev, M. Pettersson, R. Fausto, and M. Räsänen, Phys. Chem. Chem. Phys. 7, 743 (2005). [5] L. Khriachtchev, J. Mol. Struc. 880, 14 (2008). [6] K. A. E. Meyer, M. A. Suhm, submitted. [7] K. A. E. Meyer, M. A. Suhm, J. Chem. Phys. 147, 144305 (2017).

Session B

(16:00-16:30)


17

Vibrational spectroscopy: combing experiment and theory to determine the Gibbs energy of complex formation.

Anne S. Hansen1, Emil Vogt1 and Henrik G. Kjaergaard1

1Department of Chemistry, University of Copenhagen, Copenhagen Ø, Denmark

Hydrogen bound bimolecular complexes are detected in the gas phase at room temperature with infrared spectroscopy, and via the observation of XH-stretching vibrations, Gibbs energies of complex formation are determined. The detection of the hydrogen bound complexes is illustrated. The XH bond directly involved in hydrogen bonding is significantly perturbed upon complexation, resulting in an XH-stretching redshift. The magnitude of a redshift reflects the hydrogen bond strength, and is found to correlate linearly with the kinetic energy density between the hydrogen bond donor (XH) and acceptor (Y) obtained from a non-covalent interaction analysis. [1] The complex strength is determined from the Gibbs energy of complex formation. These Gibbs energies are difficult to calculate accurately using quantum chemical methods. However, observed transition intensities of the hydrogen bound complexes are combined with corresponding theoretical intensities, to determine the composition of the reaction mixtures and thus the Gibbs energy. The reliability of this method is tested for a series of alcohol·dimethylamine complexes, where dual determination of the Gibbs energy is possible from detection of both the OH- and the NH-stretching vibrations. [2,3] The Gibbs energy is determined for series of complexes with OH and NH bond donors while systematically changing the hydrogen bond acceptor. More recently hydrated complexes involving S and N acceptor atoms have been investigated. Detection of some hydrated complexes succeeded, and analysis of their infrared spectra enabled determination of their Gibbs energies. [4]

[1] J. R. Lane, A. S. Hansen, K. Mackeprang and H. G. Kjaergaard. “Kinetic energy density as a predictor of hydrogen-bonded OH-stretching frequencies.” J. Phys. Chem. A, 2017, 121, 3452-3460. [2] L. Du, K. Mackeprang and H. G. Kjaergaard. “Fundamental and overtone vibrational spectroscopy, enthalpy of hydrogen bond formation and quilibrium constant determination of the methanol-dimethylamine complex.” Phys. Chem. Chem. Phys., 2013, 15, 10194–10206. [3] A. S. Hansen, L. Du and H. G. Kjaergaard. “The effect of fluorine substitution in alcohol-amine complexes.” Phys. Chem. Chem. Phys., 2014, 16, 22882-22891. [4] A. S. Hansen and H. G. Kjaergaard. “Dimethyl sulfoxide complexes detected at ambient conditions.” J. Phys. Chem. A, 2017, 121, 6046- 6053.

Session B

(16:30-17:00)


18

Vibrational averaging of NMR and ESR properties with VPT2: how far have we come? Stephan P. A. Sauer1, Patrick A. Aggelund1, Frederick C. Østergaard1, Rasmus Faber1

1University of Copenhagen, Department of Chemistry

The theory and calculation of vibrational corrections to ground state molecular properties of molecules will be discussed [1]. The importance of these corrections will be illustrated with examples for isotope effects and the temperature dependence of NMR indirect nuclear spin-spin coupling constants [2,3,4,5,6]. The level of theory in the electronic structure theory calculations will be discussed and illustrated with recent calculations of NMR spin-spin coupling constants at the CCSD level [6,7,8]. Finally preliminary results for vibrational corrections to ESR hyperfine coupling constants will be presented [8,9]. [1] R. Faber, J. Kaminsky, S. P. A. Sauer, Rovibrational and temperature effects in theoretical studies of NMR parameters in K. Jackowski and M. Jaszuński eds.,Gas Phase NMR, Royal Society of Chemistry (2016), Chapter 7, pp. 218-266 [2] R. D. Wigglesworth, W. T. Raynes, S. P. A. Sauer, J. Oddershede, The calculation and analysis of isotope effects on the nuclear spin-spin coupling constants of methane at various temperatures, Mol. Phys. 92, 77-88 (1997) [3] R. D. Wigglesworth, W. T. Raynes, S. P. A. Sauer, J. Oddershede, Calculated spin-spin coupling surfaces in the water molecule; prediction and analysis of J(O,H), J(O,D) and J(H,D) in water isotopomeres, Mol. Phys. 94, 851-862 (1998) [4] R. D. Wigglesworth, W. T. Raynes, S. Kirpekar, J. Oddershede, S. P. A. Sauer, Nuclear spin-spin coupling in the acetylene isotopomers calculated from ab initio correlated surfaces for 1J(C,H), 1J(C,C),2J(C,H) and 3J(H,H), J. Chem. Phys. 112, 3735-3746 (2000) [5] A. Yachmenev, S. N. Yurchenko, I. Paidarová, P. Jensen, W. Thiel, S. P. A. Sauer, Thermal averaging of the indirect nuclear spin-spin coupling constants of ammonia: the importance of the large amplitude inversion mode, J. Chem. Phys. 132, 114305 (2010) [6] R. Faber and S. P. A. Sauer, On the Discrepancy between Theory and Experiment for the F-F spin-spin Coupling Constant of Difluoroethyne, Phys. Chem. Chem. Phys. 14, 16440-16447 (2012) [6] R. Faber, S. P. A. Sauer, SOPPA and CCSD vibrational corrections to NMR indirect spin-spin coupling constants of small hydrocarbons, AIP Conf. Proc. 1702, 090035 (2015) [7] P. A. Aggelund, M. J. Dahlin, Y. Theibich, L. I. Ø. Kristensen, S. P. A. Sauer (to be published) [8] P. A. Aggelund, Master Thesis, University of Copenhagen, 2018 [9] R. Nielsen, Master Thesis, University of Copenhagen, 2017

Session C

(8:30-9:00)


19

Weak intramolecular interaction effects on the structure and fir spectra of molecules with various torsional motions: ethylene glycol and its isotopologues

Senent ML1, Boussessi R1

1Departamento de Química y Física Teóricas, Instituto de Estructura de la Materia, CSIC, Serrano 121, Madrid 28006

Many medium-sized organic molecules present non-rigidity. Torsional motions and, in general, large amplitude motions, intertransform the different conformers that can stabilize by the formation of intramolecular hydrogen bonds. In the low energy regions of the potential energy surface, these hydrogen bonds can determine the symmetry and they can play important roles on the structure and on the low vibrational energy levels. A variational procedure of reduced dimensionality based on CCSD(T)-F12 calculations is applied to understand the far infrared spectrum of various isotopologues of cis-gauche-Ethylene-Glycol [1,2] where three interacting internal rotations intertransform all the minima. The anisotropy of the surface in the gauche region converts the assignment and classification of the torsional levels into a tricky puzzler. [1] Boussesi, et al. J.Chem.Phys., 144, 164110 (2016) [2] Boussesi & Senent (in preparation)

Session C

(9:00-9:30)


20

Vibrational computations beyond the harmonic approximation: from molecules to periodic systems

Falk Richter1, Michel Rérat1, Roberto Dovesi2, Philippe Carbonniere1

1CNRS/Université de Pau et des Pays de l’Adour, IPREM, UMR5254, 2 avenue du Président Angot, 64000 Pau, France

2Dipartimento di Chimica NIS (Nanostructured Interfaces and Surfaces) Centre, Università di Torino, via Giuria, I-10125 Torino, Italy

The talk deals with time independent (static) vibrational computations beyond the harmonic approximation as implemented in the development version of CRYSTAL code [1]. The Vibrational Configuration Interaction procedures from Harmonic Oscillators (VCI-HO) [2] or Vibrational Size Consistent Field (VCI-VSCF) basis sets are detailed. The Anharmonic treatment of Infrared (IR) and RAMAN activities, which provide information about intensities of overtones and combination bands, are also presented. These implementations are illustrated by several examples namely the characterization of the VNxHy defects in diamond [3,4]. The construction of the anharmonic force field and its improvement from the concept of Adaptative Generation of Potential Energy Surfaces (AGAPES) [5] is discussed. On that point, the performance of AGAPES is discussed along with the possibility of achieving near linear scaling of sample points with the molecule. This approach seems particularly well suited for a better description of soft modes and double well problems as illustrated through the example of the Formamide [6] and the formic acid double minimum case [7]. Returning to the computation of (quartic or even sextic) force fields for large periodic systems, a new and automated strategy allowing the production of reduced force fields is presented. The strategy concerns the choice of the most pertinent mode-mode couplings before the elaboration of the grid points at which electronic structure computations are performed. Reliability and gains in terms of computational savings are presented through the examples of molecular systems from 5 to 12 atoms and periodic systems such as Aragonite and VNxHy defect in diamond. [1] R. Dovesi, R. Orlando, A. Erba, C. M. Zicovich-Wilson, B. Civalleri, S. Casassa, L. Maschio, M. Ferrabone, M. De La Pierre, P. D’Arco, Y. Noel, M. Causa, M. Rerat, B. Kirtman. Int. J. Quantum Chem. 114, 1287 (2014). [2] P. Carbonniere, A. Dargelos, C. Pouchan. Theor. Chem. Acc. 125, 543 (2010). [3] F.S. Gentile, S. Salustro, M. Causa, A. Erba, P. Carbonnière, R. Dovesi, Phys. Chem. Chem. Phys. 19, 22221 (2017). [4] S. Salustro, F.S. Gentile, A. Erba, P. Carbonnière, K. E. El-Kelany, R. Dovesi, Carbon (2018), in press. [5] F. Richter, P. Carbonniere, A. Dargelos, C. Pouchan, J. Chem. Phys. 136, 224105 (2012). [6] F. Richter, F. Thaunay, D. Lauvergnat, P. Carbonniere, J. Phys. Chem. A 119, 11719 (2015). [7] F. Richter, P. Carbonniere, J. Chem. Phys. 148, 064303 (2018).

Session C

(9:30-10:00)


21

Absolute Vibrational Transition Intensities of Bimolecular Complexes

Emil Vogta, Lauri Halonenb, Henrik G. Kjaergaarda

a) Department of Chemistry, University of Copenhagen, Copenhagen Ø, Denmark b) Department of Chemistry, University of Helsinki, Helsinki, Finland

Experimental determination of the thermodynamic stability of hydrogen bonded bimolecular complexes is not trivial as the pressure of each species involved in the equilibrium (monomers and complex) needs to be determined accurately, yet often span several orders of magnitude. We combine vibrational spectroscopy and theory as an alternative approach to address the task of accurate pressure determination of both monomers and the complex. With this approach, the pressure of the complex is determined by associating a measured and a calculated intensity of a vibrational transition unique to the complex. The pressure of each monomer is determined directly in the experiment. A primary indicator of hydrogen-bond formation is the frequency redshift and intensity enhancement of the bonded XH-stretching fundamental transition, relative to that of the XH-stretching fundamental transition in the monomer. These changes mean that the absorption cross-section of the bonded XH-stretching fundamental transition is experimentally accessible and this transition is therefore often used to determine the pressure of the complex. However, calculating the intensity of the bonded XH-stretching fundamental transition is difficult, partly due to strong perturbations from the low frequency vibrations that arise upon complex formation (intermolecular vibrations). The Local Mode Perturbation Theory (LMPT) model was developed to improve the local mode model by accounting for the influence of the low frequency intermolecular modes [1,2] and has been successfully applied to a range of complexes [3]. However, limitations of the LMPT model were found when the model was applied to the water dimethylamine and the water trimethylamine complexes. For these complexes, a Fermi-resonance between the water bending overtone and the bonded OH-stretching fundamental transition enables a triple determination (including the free OH-stretching fundamental transition) of the pressure of the complex. We have applied van Vleck transformations to block-diagonalize the local mode Hamiltonian via perturbation theory and subsequently treat the Fermi-resonance variationally. With this approach we are able include the effect of the low frequency intermolecular modes and deal with quasi-degeneracies. We show that accurate transition frequencies and intensities can be calculated within the local mode van Vleck perturbation theory (LMVPT) framework.

[1] Mackeprang et. al, The Journal of Chemical Physics, 2014, 140(18), 184309. [2] Mackeprang et. al, The Journal of Chemical Physics, 2015, 142(9), 094304. [3] Mackeprang, K. and H.G. Kjaergaard, Journal of Molecular Spectroscopy, 2017, 334, 1-9.

Session C

(10:30-11:00)


22

Ab initio calculations for a methylfluoride-argon clusters and 𝐶𝐻 −Rg (Rg=He, Ne, Ar) clusters

S. Erfort1, M. Schneider1, B. Ziegler1, J. Meisner2 and G. Rauhut1

1University of Stuttgart, Institut für Theoretische Chemie, Pfaffenwaldring 55, 70569 Stuttgart, Germany

2Stanford University, Department: Chemistry, Stanford, California 94305, USA

Molecular clusters are an active field of research because of their importance for chemical and biophysical phenomena. In matrix isolation spectroscopy the embedding consisting of e.g. rare gases can have an effect on the molecule under investigation. It is crucial to understand these effects to seperate them from the results that are acutally desired. Because of the weak interaction and low dissociation energies both experimental and computational treatment are challenging. Predissociation spectroscopy has been a standard tool for many years and has recently been extended to rovibrational spectroscopy using a double resonance scheme (see [1] and references therein). Theoretical studies profit from increasing computational power and models as well as programs are continously enhanced now being well able to give accurate results [2-4]. In our recent studies we investigated methylfluoride-argon clusters and 𝐶𝐻 −Rg (Rg=He, Ne, Ar) clusters. The former feature three equilibrium structures with different positions for the argon atom. Geometries for these structures and the transition states were calculated at the CCSD(T)-F12/aug-cc-pVNZ (N=D,T) level. All complexes are within similar energies and thus potentially apparent e.g. in syntheses. I will briefly address the numerical challenges, especially regarding the PESs. Vibrational calculations at the VCI level show good agreement with experimental results. An effective two-particle model with fitting of the resulting one-dimensional potential using a Morse-function yields an efficient method describing the dissociation. For the 𝐶𝐻 −Rg clusters reduction from D3h to C3v symmetry was quantified and the effect of different noble gases was compared. Instanton methods were employed to study the inversion transition on the minimum energy path for the vibrational ground state with full geometry optimization at the CCSD(T)-F12/aug-cc-pVTZ level. From these calculations the energy barrier and tunnel splitting could be quantified which are to be compared with experimental results [1,5]. [1] M. Töpfer, O. Asvany, O. Dopfer et al., Double Resonance Rotational Spectroscopy of Weakly Bound Ionic Complexes: the case of floppy 𝐶𝐻 − 𝐻𝑒,To be published. [2] M. Yang, M. H. Alexander, H.-J. Werner, and R. J. Bemish, Ab initio and scaled potential energy surfaces for Ar–C2H2: Comparison with scattering and spectroscopic experiment, J. Chem. Phys. 105, 10462 (1996) [3] R. R. Toczyłowski and S. M. Cybulski, An ab initio study of the potential energy surface and spectrum of Ar–CO, J. Chem. Phys 112, 4604 (2000) [4] D. Cappelletti et al., Intermolecular interaction potentials for the 𝐴𝑟– 𝐶 𝐻 , 𝐾𝑟– 𝐶 𝐻 , and

𝑋𝑒– 𝐶 𝐻 weakly bound complexes: Information from molecular beam scattering, pressure broadening coefficients, and rovibrational spectroscopy, J. Chem. Phys., 126, 064311 (2007) [5] O. Dopfer, D. Luckhaus, Rovibrational calculations for CH3+–Rg (Rg=He, Ne): The prototype disk-and-ball dimer, J. Chem. Phys. 116, 3 (2002).

Session C

(11:00-11:30)


23

An adapted density-guided approach to potential energy surface construction using specialized vibrational coordinates and general fit-basis functions

Emil Lund Klinting1, David Lauvergnat2, Ove Christiansen1

1Department of Chemistry, Aarhus University, Denmark

2Laboratoire de Chimie Physique, Université Paris-Sud, France

A severe bottleneck in obtaining accurate anharmonic vibrational excitation energies for molecular systems is in constructing a potential energy surface (PES). This problem can to some degree be mitigated by employing an n-mode expansion scheme, combined with a method that can dynamically generate a set of grid points, such as the adaptive density-guided approach (ADGA) [1]. The ADGA is an iterative method and it is therefore essential to capture the underlying physics quickly or risk introducing unnecessary single point calculations (SPCs), which the use of appropriate fit-basis functions improve upon. Specialized fit-basis functions have shown great promise when used to represent potentials of general Morse or double-well shapes, and are clearly superior to the more standard polynomial type fit-basis functions for these [2]. This results in a decreased number of required SPCs during the potential construction and fewer terms in the analytical potential obtained from the fitting routine. Another route that can be taken in order to reduce the number of required SPCs [2] and simultaneous increase the accuracy of vibrational structure calculations [3] is to use vibrational coordinates that are more localized than normal coordinates (NCs). Interesting choices for this would include the hybrid optimized and localized coordinates (HOLCs) [3] or the flexible adaption of local coordinates of nuclei (FALCON) [4]. These coordinates can be combined with the specialized fit-basis functions to decrease the number of required SPCs even further, but also facilitate a greater degree of decoupling between modes that do not inherently interact, which provides good opportunity for screening of non-contributing mode-couplings [5]. The NCs, HOLCs and FALCONs are, however, all rectilinear vibrational coordinates and thereby risk introducing artificial correlation in the Hamilton operator. It is possible to resolve some of this, especially for stretching motions by using the HOLCs or FALCONs instead of the Ncs, but in order to truly resolve the problem of artificial correlation one will need to use curvilinear coordinates, where angles are naturally included in the set of vibrational coordinates. These provide a description that inherently follows the molecular motion, but at the cost of the simple kinetic energy operator associated with rectilinear coordinates [6]. Interfacing the ADGA directly to the Tana program [7] in order to gain access to the special class of curvilinear coordinates known as polyspherical coordinates will in these regards be expected to further improve on the results already found when employing the HOLCs or FALCONs. [1] M. Sparta and D. Toffoli, and O. Christiansen, Theor. Chem. Acc. 123, 413-429 (2009). [2] E. L. Klinting, B. Thomsen, I. H. Godtliebsen, and O. Christiansen, J. Chem. Phys. 148, 064113 (2018). [3] E. L. Klinting, C. König, and O. Christiansen, J. Phys. Chem. A 119, 11007-11021 (2015). [4] C. König, M. B. Hansen, I. H. Godtliebsen, and O. Christiansen, J. Chem. Phys. 144, 074108 (2016). [5] C. König, E. L. Klinting, and O. Christiansen, In Preparation. [6] D. Lauvergnat and A. Nauts, J. Chem. Phys. 116, 8560 (2002). [7] M. Ndong, L. Joubert-Doriol, H.-D. Meyer, A. Nauts, F. Gatti, and D. Lauvergnat, J. Chem. Phys. 136, 034107 (2012).

Session C

(11:30-12:00)


24

An ultra-cold quantum degenerate plasma: Observation of a periodic many-body system

Klaus Müller-Dethlefs and François Michels

School of Chemistry and Photon Science Institute, University of Manchester, M13 9PL, UK

Ultra-cold plasma offers interesting applications such as trapping and sympathetic cooling of large molecules or molecular clusters. Here, we report the experimental observation of a very striking periodicity in a long life-time (>0.3 ms) quantum degenerate molecular Rydberg plasma. The plasma is produced in the high-density, high-collision rate region of nitric oxide (10%) in neon (5bar) of a pulsed supersonic jet expansion by two-colour resonant excitation via the NO A-state into the high-n Rydberg threshold region close to the ionization limit. For typical plasma densities of > 1016 cm–3 the electrons should become quantum degenerate, i.e. the electron de Broglie wavelength becomes larger than the Wigner-Seitz radius a describing the particle mean distance between the particles. The time-of-flight (ToF) set-up employs two synchronous UV laser pulses to produce the plasma a few mm away from the jet nozzle. After 170𝜇s, when the plasma cloud is still ca. 130mm in front of aperture plate 1, two successive high-voltage (3.6kV) pulses P1,1 (width: 5.5𝜇s) and P1,2 (20 𝜇s), separated by a

0.2𝜇s gap are applied to ap.1. The observed ToF spectrum is shown in the l.h.s. figure (positive particle detection). The observed sharp peaks (“slices”) in the ToF spectrum follow a fully reproducible progression of (m/z) mass to charge ratios from 35 to 92.5 (blue: w.r.t. m(NO+) = 30u). From the m/z ratio one obtains the corresponding ion to electron ratios of the 12 slices (denoted in the bottom of figure), from 7/1 to 37/25. The series of magic number objects follows a periodicity for the ion/electron ratio: 14/2, 15/3, (16/4, 17/5, 18/6, 19/7), 20/8, 21/9, 22/10,

(23/11, 24/12, 25/13, 26/14), 27/15, 28/16, 29/17, (30/18, 31/19, 32/20, 33/21), 34/22, 35/23, 36/24, 37/25. These objects are manipulated by electric fields in the ToF spectrometer without being destroyed: they behave as objects with a centre of mass. These objects cannot be identified as non-covalently bound molecular clusters but they have to be interpreted as objects consisting of ions (NO+) and electrons with orders of magnitude larger “bond” distances of several hundreds of nanometers. Starting from the common textbook opinion that in many-electron atoms the electrons are quantum entangled (a deeper reason for the periodic system of the elements), one can speculate that the observation of such a periodicity in the many-body system presented here might originate from quantum entanglement. Such a plasma would provide a sympathetic cooling environment for larger molecular systems.

(m/z)/(30u/e): 7/6 11/6 14/6 3

(m/z)/(u/e): 35 55 70 90

ionselectrons

:28

4, 30

6,

40

16, 42

18, 44

20,

54

30, 56

32, 58

34,

68

44, 70

46, 72

48, 74

50

Session D

(8:30-9:00)


25

Molecular dynamics by collinear photofragmentation and atomic absorption spectroscopy

Viljanen J, Sorvajärvi T, Toivonen J

Tampere University of Technology, Laboratory of Photonics, P.O. Box 692, FI-33101 Tampere, Finland

Collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) is a recently developed optical method for analysing molecular concentrations and their kinetics. [1,2] The technique is based on the fragmentation of a precursor molecule and the detection of the fragment atoms via absorption spectroscopy on a common laser beam path. It has been applied to monitor concentrations of the precursors KCl and KOH in thermal conversion applications. CPFAAS studies have focused on precursor molecule concentration analysis using the maximum absorbance right after the photofragmentation. Sample lengths ranging from 1 cm to 10 m have been demonstrated in the studies [2]. Here we concentrate on relaxation dynamics after the maximum absorbance, and show that it can be utilized in kinetic analysis. We demonstrated the first direct measurement of the bond dissociation energy of KO2 [1] and also calibrated the method to retrieve local oxygen concentration and temperature due to their effect on the kinetics [3]. Lastly, other potential application areas of the technology are discussed.

Figure 2. Schematic presentation of typical CPFAAS measurement arrangement showing the laser beam path.

References [1] T. Sorvajärvi, et al., Rate Constant and Thermochemistry for K + O2 + N2 = KO2 + N2, The Journal of Physical Chemistry A 119, 3329-3336 (2015). [2] T. Sorvajärvi, N. DeMartini, J. Rossi, and J. Toivonen, In situ measurement technique for simultaneous detection of K, KCl, and KOH vapors released during combustion of solid biomass fuel in a single particle reactor, Applied Spectroscopy 68, 179-184 (2014). [3] J. Viljanen, T. Sorvajärvi, and J. Toivonen, In situ laser measurement of oxygen concentration and flue gas temperature utilizing chemical reaction kinetics, Optics letters 42, 4925-4928 (2017).

K + O ⇌ KO

Session D

(9:00-9:30)


26

Laser-induced Quantum Control of Molecular Processes

Niels Engholm Henriksen

Department of Chemistry, Technical University of Denmark, DK-2800 Lyngby, Denmark Lasers are an important tool in energy-resolved as well as time-resolved spectroscopy. In addition, laser light can be used as an active tool to control the dynamics of molecules. Phase coherence of laser light plays a key role and to that end - for a fixed laser bandwidth - it is possible via pure phase modulation to transfer the phase coherence of laser light to the control of quantum interferences in molecular systems. Laser-molecule interactions via static or induced dipole terms, give rise to resonant or non-resonant interactions the latter in the form of the dynamic Stark effect, equivalent to impulsive Raman scattering [1]. In this talk, we will illustrate these principles, with theoretical/computational studies focusing on control via pure phase modulation of laser light. Illustrations include: (i) weak-field control of photodissociation [2,3], (ii) elimination of non-linear light-matter interactions [4], and (iii) selective conversion of enantiomers in a racemic mixture via phase-modulated non-resonant (800 nm) laser pulses [5]. [1] E.F. Thomas and N.E. Henriksen, J.Chem.Phys. 144, 244307 (2016). [2] A. Garcia-Vela and N.E. Henriksen, J.Phys.Chem.Lett. 6, 824 (2015). [3] A.K. Tiwari and N.E. Henriksen, J.Chem.Phys. 144, 014306 (2016). [4] C.-C. Shu, D. Dong, I.R. Petersen, and N.E. Henriksen, Phys.Rev.A. 95, 033809 (2017). [5] E.F. Thomas and N.E. Henriksen, J.Phys.Chem.Lett. 8, 2212 (2017).

Session E

(10:00-10:30)


27

Smolyak scheme and on-the-fly kinetic energy operator, an efficient combination: application to malonaldehyde in 21D.

David Lauvergnat1, André Nauts1,2

1Laboratoire de Chimie Physique, CNRS, Univ. Paris-Sud, Université Paris-Saclay, France 2 Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain,

Belgium

To efficiently solve the Schrödinger equation for the nuclear motions using standard approaches, the wave functions or wave packets have to be expanded on a compact basis set which has to be adapted to the molecule or process under study. When dealing with systems with a large number of degrees of freedom, n, two fundamental steps are to be taken: (i) Choosing physically well-adapted coordinates. In this context of curvilinear coordinates, the kinetic energy operator (KEO) is more easily calculated in a numerical approach, [1,2] such as TNUM. [3] (ii) Avoiding the exponential scaling as function of n. In this case, the tensor-product representation must be substituted by another scheme such as the Smolyak representation. [4,5] Recent calculations show that, up-to 12 degrees of freedom, simulations are tractable within the Smolyak approach. [6,7] However, calculations for larger systems have not yet been performed. Indeed, both steps require a large amount of memory. To overcome this limitation, we use the following strategies: (i) Numerical KEO: in the usual approach, about n2/2 terms (associated to the metric tensor G) need to be stored on the full grid. To avoid this, we used an on-the-fly strategy, in which the metric tensor is calculated when needed and the KEO is expressed as a curvilinear Laplacian operator. [8] (ii) Smolyak scheme: the action of an operator such as the Hamiltonian, H, on a wave function requires its transformation from the basis set to the grid (and reverse) and, in the most efficient numerical implementations, a large intermediate vector is needed. Avila and Carrington [9] show that it is possible to avoid this large vector for a collocation scheme. In our new implementation, we show that it is possible to generalize this idea and also to be able to get an efficient parallelization. In the Smolyak approach, the key point is to replace a large tensor-product by several selected small tensor-products, 𝑺ℓ ⨂ ⋯ 𝑺ℓ (generally a large number). In this case, the wave function is represented as a sum of small contributions on the selected small tensor-products:

|𝛹⟩ = 𝐷ℓ ,ℓ ,…ℓ ∙ 𝛹𝑺ℓ ⨂⋯𝑺ℓ ∑ ℓ

For each coordinate, i, the parameters, ℓ , enable to define the size of the basis sets or the grids, 𝑆ℓ and the selection of the terms in the sum is performed by means of the parameter LS. Furthermore, the operations (grid/base transformation, operator action ...) on each tensor-product contribution are completely independent from one another and are almost identical to standard operations such as the FBR/DVR transformations. Application to the calculation of the tunnelling splitting of malonaldehyde in 21D will show the efficiency of this combination of these two schemes. [1] R. Meyer, J. Mol. Spectrosc. 76 (1979) 266–300. [2] E. Mátyus, G. Czakó, A.G. Császár, J. Chem. Phys. 130 (2009) 28–39. [3] D. Lauvergnat, A. Nauts, J. Chem. Phys. 116 (2002). [4] S.A. Smolyak, Sov. Math. Dokl. 4 (1963) 240. [5] G. Avila, T. Carrington, J. Chem. Phys. 131 (2009) 174103. [6] G. Avila, T. Carrington, J. Chem. Phys. 134 (2011) 054126. [7] D. Lauvergnat, A. Nauts, Spectrochim. Acta Part A 119 (2014) 18–25. [8] A. Nauts, D. Lauvergnat, Mol. Phys. XXX (2018) 1–9. DOI: 10.1080/00268976.2018.1473652 [9] G. Avila, T. Carrington, J. Chem. Phys. 147 (2017) 064103.

Session E

(10:30-11:00)


28

On the gas-phase formation of the HCO radical: accurate quantum study of the H+CO radiative association

T. Stoecklin1, P. Halvick1, H.-G. Yu2, G. Nyman2, Y. Ellinger3

1Institut des Sciences Moléculaires, Université de Bordeaux, France 2Department of Chemistry and Molecular Biology, University of Gothenburg, Sweden

3Université Pierre-et-Marie-Curie, France

The roles of gas-phase and gas-grain processes in the interstellar medium (ISM) are important to know for understanding the chemical evolution of the ISM. In this work we investigate the formation of HCO through radiative association. In radiative association two species collide and during the collision a photon is emitted, which carries away enough energy that the fragments stick together and end up in a bound state of the forming molecule. The emission of the photon is an improbable event giving small cross sections for molecule formation through radiative association. However, since the ISM is so dilute, energy loss by three-body collisions are even less likely. Thus radiative association can still be an important process for forming new molecules, particularly in dust poor regions. Successful experimental measurements of radiative association rate constants are very few due to the very small cross sections. It is thus of interest to make theoretical calculations to estimate these rate constants. Here we perform quantum dynamical calculations of the radiative association cross sections and rate constants for the formation of HCO through radiative association. HCO may be an important species in the formation of complex organic molecules in space. It has for instance been proposed that a possible route to methanol could be CO HCO H2CO H3CO H3COH To investigate the first step in this mechanism we employ a recent 3D potential energy surface for HCO which is based on high level ab initio calculations and we perform new ab initio calculations to obtain the 3D dipole moment surfaces that we require. We then perform quantum dynamics calculations for several values of the total angular momentum, but a J-shifting procedure is used to obtain reaction probabilities for additional J-values allowing us to obtain the cross sections and rate constants. The thermal rate constants that we calculate are so small that the gas-phase H+CO radiative association in a cold interstellar medium cannot be the process in the first step of the sequence shown above leading to the formation of methanol.

Session E

(11:00-11:30)


29

Anharmonic Wavefunctions and Franck-Condon factors

Ove Christiansen1

1Aarhus University, Denmark

I will describe some overall features of our procedures for constructing potential energy surfaces and anharmonic wave functions using our adaptive density guided approach (ADGA) and vibrational configuration interaction (VCI) and vibrational coupled cluster (VCC). I will subsequently specifically discuss the possibilities for computations for larger molecular systems before focusing on new approaches for the computation of Franck-Condon factors. I will discuss how we specifically can use vibrational configuration interaction anharmonic wave functions to compute Franck Condon factors. Examples for model systems and small molecules will be given as well as for thiophenes.

Session E

(11:30-12:00)


30

Posters Mostafa Abedi

Excited-State Solvation Structure of Transition Metal Complexes from Molecular Dynamics Simulations

Ayad Bellili Intermolecular Interactions in Supercritical Carbon Dioxide:

CO2-Philicity and Reactivity

Rahma Boussessi The Performances of DFT Methods in the Prediction of Sextic Centrifugal Distortion

Constants for Astrochemical Molecules: Oxirane and Ethyl Mercaptan

Benjamin Normann Frandsen Identification of OSSO as a Near-UV Absorber in the Venusian Atmosphere

Mads Bøttger Hansen

Extended single-reference vibrational coupled cluster for the description of molecular double-well systems

Gulce Ogruc Ildiz

Structure and Spectroscopic Properties of Nickel(II) Dimethylxanthate

Alexander Kjaersgaard Selenium acceptor hydrogen bonds in the gas phase

Diana Madsen

Anharmonic Vibrational Spectra from Double Incremental Potential Energy and Dipole Surfaces

Marta Lopez Vidal A new and efficient EOM-CCSD framework to model X-ray absorption spectroscopy

Alexandre Paolo Voute High-Resolution Synchrotron Terahertz Investigation of the Large-Amplitude

Hydrogen Bond Librational Band of (HCN)2


31

Excited-State Solvation Structure of Transition Metal Complexes from Molecular Dynamics Simulations

Mostafa Abedi1, Gianluca Levi,1 Niels E. Henriksen,1 Mátyás Pápai,1,2 and Klaus B.

Møller1

1Department of Chemistry, Technical University of Denmark, 2800 Kongens Lyngby, Denmark.

2Wigner Research Center for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.

It has been experimentally evidenced that excited-state photophysical and photochemical properties of transition metal complexes (TMCs) can be strongly affected by the surrounding environment, such as solvent [1]. In this regard, computational chemistry tools can play a key role in obtaining detailed insights into the effect of the solvent. Hybrid quantum mechanics/molecular mechanics (QM/MM) simulations is the most common approach to characterize the solvation structure around a TMC. However, this method does not allow long simulations and high-resolution sampling due to its high computational cost. In this work, we suggest an efficient alternative to describe the excited-state solvation structure. Using classical molecular dynamics (MD) simulations, we assess the performance of several most-used partial atomic charge (PAC) methods against QM/MM MD for characterization of the excited-state solvation structure of four prototypical TMCs. We have found that the selection of an appropriate PAC method is dependent on the denticity of the ligands, coordination number of the metal and type of the solvent. Furthermore, for TMCs that show a free direct coordination site a careful choice of the PAC method should be considered. Overall, the results show that by applying ChelpG [2] or CM5 [3] PAC methods in fast classical MD simulations, one can provide valuable information about the solvation structure of TMCs with the accuracy of QM/MM MD (see Fig. 1).

Fig. 1. The RDFs, g(r), of the Ru-O(w), Fe-N(ACN) and Cu-N(ACN) pairs of [Ru(bpy)3]2+, [Fe(bmip)2]2+ and [Cu(phen)2]+, respectively, obtained from classical MD, using ChelpG and CM5 PAC methods, and QM/MM BOMD simulations in water (w) and acetonitrile (ACN) in the GS and excited state. [1] A. O. Dohn, K. S. Kjær, T. B. Harlang, S. E. Canton, M. M. Nielsen and K. B. Møller, Inorganic Chemistry, 2016, 55, 10637–10644. [2] C. M. Breneman and K. B. Wiberg, Journal of Computational Chemistry, 1990, 11, 361–373. [3] A. V. Marenich, S. V. Jerome, C. J. Cramer and D. G. Truhlar, Journal of Chemical Theory and Computation, 2012, 8, 527–541.

Posters


32

Intermolecular Interactions in Supercritical Carbon Dioxide: CO2-Philicity and Reactivity

A. Bellili,1 W. Harb,2 M. F. Ruiz-López,1 F. Ingrosso1

1Laboratoire de Physique et Chimie Théoriques, UMR 7019 Université de Lorraine-CNRS, Nancy, France.

2Faculty of Sciences, Holy Spirit University of Kaslik, Jounieh, Lebanon.

Supercritical solvents are receiving increasing attention as potential candidates toward the design of safer solvents, according to the principles of Green Chemistry. In the case of one of the most employed ones, supercritical CO2 (scCO2), a molecular understanding of the intermolecular interactions taking place with this molecule has allowed a significant improvement of its solvation power, opening the door to wider industrial applications.[1] In the past years, our theoretical studies provided a deeper understanding of such interactions and guided us to propose macromolecular systems to be used as ‘solubilizers’, leading to the synthesis and the characterization of the first inclusion complex in scCO2.[2] More recently, we are treating reactive systems in this medium, a key topic for the development of novel industrial processes responding to societal needs in terms of environmental impact and biocompatibility. We shall report the preliminary results obtained for a reaction involving an iminophosphorane and CO2, which was carried out experimentally in scCO2[3] and which represents an example of a process fulfilling the principle of ‘atom economy’, since carbon dioxide behaves at the same time as a reactant and as the reaction medium. In particular, we shall present how different levels of theory perform to model such reaction, and the methodology that we are employing to take into account the thermodynamic properties of the solvent in the supercritical phase.

Figure 1. Schematic representation of the potential energy surface for the reaction between an iminophosphorane and carbon dioxide.

[1] E.J. Beckman Chem Commun 17, 1885 (2004). [2] F. Ingrosso, M.F. Ruiz-López, ChemPhysChem 18, 2560 (2017); F. Ingrosso et al. Chem. Eur. J. 22, 2972 (2016); F. Ingrosso, M.F. Ruiz-López J. Phys. Chem. A 122, 1764 (2018). [3] S. Menuel et al. Tetrahedron Lett. 46, 3307 (2005). A. Scondo et al. J. Supercrit. Fluids 53, 60 (2010).

Posters


33

The Performances of DFT Methods in the Prediction of Sextic Centrifugal Distortion Constants for Astrochemical Molecules: Oxirane and Ethyl Mercaptan

Rahma Boussessi1,2, Nicola Tasinato2, Andrea Pietropolli Charmet3, Paolo Stoppa3 and

Vincenzo Barone2

1 Institute of Chemistry of Organometallic Compounds CNR, Pisa, Italy 2 Scuola Normale Superiore, Pisa, Italy.

3 Università Ca’ Foscari Venezia, Dipartimento di Scienze Molecolari e Nanosistemi, Mestre Venezia, Italy

Advances in microwave and infrared spectroscopy in recent years have made it possible to determine some or all of the sextic centrifugal distortion constants of a variety of simple molecules of astrochemical interest. For the purpose, reliable computational calculations are indispensable for interpreting experimental data and guiding new measurements. The performances of several model chemistries in yielding reliable sextic centrifugal distortion constants have been recently investigated [1,2]. In the present contribution, we carried out a systematic study on the use of the hybrid B3LYP and the double-hybrid B2PLYP functionals in combination with Jensen’s polarization-consistent pc-seg-n basis sets [3-5] and Dunning’s correlation-consistent basis sets in the prediction of sextic centrifugal distortion constants for a test set of astrochemical molecules. In particular, we performed the investigation for oxirane (c-C2H4O) and the two conformers trans and gauche of the non-rigid molecule ethyl mercaptan (CH3CH2SH). On the one side, one of the aims of the present work was to validate the recent development in the Gaussian 16 software [6] in the calculation of sextic centrifugal distortion constants for asymmetric and symmetric top molecules. On the other, we investigated the convergence behavior of sextic centrifugal distortion constants computed by using the pc-seg-n basis sets and compared their performances to the correlation consistent Dunning’s basis sets of triple-ζ quality, cc-pVTZ and aug- cc-pVTZ. In addition, we checked the performance of the minimal augmented diffuse basis set maug-cc-pVTZ and that in which d-functions on H atoms have been removed, maug-cc-pVTZ-dH. We employed Jensen segmented polarization consistent basis sets pc-seg-n (for n=0,1,2,3,4) downloaded from EMSL basis set library [7]. Additional calculations were carried out by using the B3LYP functional in conjunction with the SNSD [8,9] basis set. Since accurate computed values are available in literature, obtained from calculations performed at the CCSD(T) level of theory, our density functional theory (DFT) predicted values were compared to both theoretical and experimental available data [10-16]. The effects related to the size of basis sets are presented and discussed. [1] A. Pietropolli Charmet, Y. Cornaton, J. Mol. Struct. 1160 (2018) 455. [2] A. Pietropolli Charmet, P. Stoppa, N.Tasinato, S. Giorgianni, J. Mol. Spectrosc. 335 (2017) 117. [3] F. Jensen, J. Chem. Theory Comput. 10 (2014) 1074. [4] D. Feller, J. Comp. Chem. 17 (1996) 1571. [5] K. L. Schuchardt, B. T. Didier, T. Elsethagen, L. Sun, V. Gurumoorthi et al., J. Chem. Inf. Model. 47 (2007) 1045. [6] Gaussian 16, Revision A.03, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb et al., Gaussian, Inc., Wallingford CT, 2016. [7] EMSL (2016) Basis Set Exchange. Environment Molecular Sciences Laboratory, Richland. https://bse.pnl.gov/bse/portal. [8] I. Carnimeo, C. Puzzarini, N. Tasinato, P. Stoppa, A. Pietropolli Charmet, et al., J. Chem. Phys. 139 (2013) 074310. [9] Available at <http://dreamsnet.sns.it/downloads> (accessed on December 14, 2016). [10] C. Puzzarini, M. Biczysko, J. Bloino, V. Barone, ApJ. 785 (2014) 107. [11] C. Puzzarini, A. Ali, M. Biczysko, V. Barone, ApJ. 792 (2014) 118. [12] C.Medcraft, C.D.Thompson, E.G. Robertson, D.R.T. Appadoo, D. NcNaughton, ApJ. 753(2012)18. [13] L. Kolesniková, B. Tercero, J. Cernicharo, J. L. Alonso, A. M. Daly et al., ApJL. 784 (2014) L7. [14] C.Puzzarini, M.L.Senent, R.Domínguez-Gómez, M. Carvajal, M. Hochlaf et al., ApJ. 796(2014)50. [15] H. S. P. Müller, A. Belloche, L.-H Xu, R. M. Lees, R. T. Garrod et al., A&A 587 (2016) A92. [16] M.L. Senent, C. Puzzarini, R. Domínguez-Gómez, M. Carvajal, J. Chem. Phys. 140(2014)124302.

Posters


34

Identification of OSSO as a Near-UV Absorber in the Venusian Atmosphere

Benjamin N. Frandsen1, Paul O. Wennberg2, and Henrik G. Kjaergaard1

1 Department of Chemistry, University of Copenhagen, Copenhagen Ø, Denmark 2 Division of Engineering and Applied Science and Division of Geological and Planetary

Sciences, California Institute of Technology, Pasadena, California, USA

We have predicted the existence of two sulfur oxides in the Venusian atmosphere, cis- and trans-OSSO. Sulfur monoxide (3SO) is a known constituent of the middle atmosphere on Venus and based on computational chemistry we found that two 3SO molecules readily react to form cis- and trans-OSSO through a barrierless reaction. Furthermore, we calculated the UV-Vis spectrum of cis- and trans-OSSO and found that they spectrally fit the enigmatic UV absorber in the Venusian atmosphere. Our estimate of cis- and trans-OSSO altitude dependent concentrations show that they can be abundant enough at the right altitudes to account for the enigmatic UV absorption.

[1] B. N. Frandsen, P. O. Wennberg, and H. G. Kjaergaard, Accepted.Geophys. Res. Lett. (2016) [2] R. Haus et al. (2016) Icarus, 272, 178-205.

Posters


35

Extended single-reference vibrational coupled cluster for the description of molecular double-well systems

Mads Bøttger Hansen1, and Ove Christiansen1

1 Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark

In vibrational coupled cluster (VCC) theory the vibrational state has an exponential parametrization based on a single-configuration reference state, oftenmost obtained from a mean-field vibrational self-consistent field (VSCF) calculation;

|VCC⟩ = exp (T)|VSCF⟩

Here T is the cluster operator, the effect of which is to generate a superposition of configurations for which some of the modes have been excited w.r.t. the reference state. By truncating T at a certain level n, i.e. by only allowing up-to-n-mode excitations, a hierarchy of VCC[n] methods are achieved that converge towards the full vibrational configuration interaction (FVCI) solution which is exact within the chosen one-mode basis but is much too costly to compute for anything but the smallest molecules. Due to the ansatz VCC works very well when the reference state is dominant in the FVCI solution, and fortunately this is oftenmost the case for the ground states of molecules vibrating around a well-defined electronic energy minimum. Excited state energies can subsequently be accurately obtained from response theory. Molecules possessing double-wells, on the other hand, can have several dominant configurations due to the near-degeneracy of the bound doublewell states – our goal is then to adapt VCC to describe vibrational correlation efficiently also in these cases. Instead of making a full-blown multi-reference VCC formulation, the theory of which would be both hard to develop, implement and apply, we have introduced an extended single-reference model where certain higher-than-n-mode excitations are allowed in T by allowing the doublewell modes not to count towards the n-mode limit. By doing so all one-mode states for the double-well mode(s) have the same excitation space and are thus described equivalently in practice even though a certain reference is singled out in the ansatz. We will look at how this model performs when calculating ground and excited state energies for small and medium-sized molecules containing amino and hydrogen transfer groups

Posters


36

Structure and Spectroscopic Properties of Nickel(II) Dimethylxanthate

Gulce Ogruc Ildiza,b

aFaculty of Sciences and Letters, Department of Physics, Istanbul Kultur University, Atakoy Campus, Bakirkoy 34156, Istanbul, Turkey.

bCQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.

The structural and spectroscopic characterization of nickel(II) dimethyl xanthate is described. DFT calculations revealed that the isolated molecule of the complex may exist in two nearly degenerated conformers (cis and trans, with the methyl groups of the ligand molecules positioned the same side or in opposite sides of the molecule, respectively; see Figure). In the crystalline compound, only the trans conformer is present, with the individual molecules in the crystal exhibiting a slightly distorter geometry from the D2h symmetry point group due to intermolecular interactions. DFT and TD-DFT calculations were also carried on in order to interpret and help achieving full spectral assignment of the infrared spectra of the crystal and of the UV-vis absorbance spectrum of the complex in CHCl3 solution. The latter revealed that metal to ligand charge transfer is relevant in determining the electronic properties of the studied complex. On the other hand, the IR data point to relatively weak intermolecular interactions in the solid material, since the intramolecular vibrational potential describing the vibrations of the isolated molecule appears to be only slightly affected by the intermolecular potential. This conclusion is also supported by the structural data, the calculated equilibrium geometry for the trans isolated conformer and that found for the molecules within the crystal being very similar. Nevertheless, it was possible to identify the most important intermolecular interactions present in the crystal of the complex as being of the S···H type.

DFT optimized geometries of the trans and cis conformers of complex 1 as isolated species.

Acknowledgements: The Coimbra Chemistry Centre (CQC) is supported by FCT, through the project UI0313/QUI/2013, also co-funded by FEDER/COMPETE 2020-EU. The Project MATIS is also acknowledged for partial financial support to this study. The authors would also like to acknowledge Drs. Girijesh Kumar, Rakesh Kumar and Ahmad Husain (Department of Chemistry & Centre for Advanced Studies in Chemistry, Panjab University Chandigarh, Chandigarh, India, and Department of Chemistry, DAV University Jalandhar, Punjab, India) for their active participation in part of the research herein presented.

Posters


37

Selenium acceptor hydrogen bonds in the gas phase

Alexander Kjaersgaard1 Joseph R. Lane2 and Henrik G. Kjaergaard1

1 Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark

2 School of Science, University of Waikato, Private bag 3105, Hamilton 3240, New Zealand

Hydrogen bonded complexes, bound with a selenium acceptor atom, have been observed experimentally, at room temperature, using several alcohol donors. The redshift of these OH···Se hydrogen bonds are determined. In addition, the unit less equilibrium constant of formation of hydrogen bonded complex is determined for a weaker donor molecule, tert-butanol (t-BuOH), as well as a stronger donor molecule 2,2,2-trifluoroethanol (TFE). Both redshift and the equilibrium constant are compared to that of the corresponding OH···O and OH···S complexes. Non Covalent Interaction (NCI) analysis have been used to visualize the hydrogen bonded isosurface and theoretically assess the strength of the selenium acceptor atom hydrogen bond compared to that of oxygen or sulfur acceptor atoms.

Fig 1: Observed redshift, in cm-1, of several hydrogen bonded complexes, consisting of one of the five alcohol donors: Methanol (MeOH), ethanol (EtOH), tert-butanol (t-BuOH), 2,2,2-trifluoroethanol (TFE) and phenol (PhOH). Combined with one of three acceptor molecules: Dimethylether (OH···O), dimethylsulfur (OH···O) or dimethylselenide (OH···Se).

Posters


38

Anharmonic Vibrational Spectra from Double Incremental Potential Energy and Dipole Surfaces

Diana Madsen1 , Carolin König2 , Ove Christiansen1

1 Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark

2 Faculty of Mathematics and Natural Sciences, Kiel Nano, Surface and Interface Science (KiNSIS), Max-Eyth-Strasse 1, Germany

Linearly scaling potential energy- and dipole surfaces have been generated by a so-called double incremental approach[1] and applied to calculate anharmonic vibrational spectra for different molecules. In the double-incremental approach, the surfaces are expressed as an expansion including up to a certain number of vibrational modes coupling simultaneously and an incremental evaluation of the energy or dipole. The incremental evaluation is made by dividing the molecules into fragments and including combinations of these fragments in an incremental fashion. In order to get computational savings, coordinates with well-defined locality have been applied. These coordinates are either local to one fragment or spanning multiple fragments. By introducing auxiliary coordinates for the spanning coordinates, new coordinates spanning only some fragments can be obtained. In this way, a linear scaling of both the number of single points and accumulated cost of single points can be obtained. However, the auxiliary coordinates require an extra transformation, which leads to an extra error. Consequently, there have been two kinds of errors to investigate the impact of: 1) the fragmentation error and 2) the transformation error. The results have shown that for some systems like para tetra-phenyl the calculated spectra show insignificant fragmentation and transformation errors. The double incremental approach is potentially a game-changer regarding pushing the limits of molecular sizes for which accurate anharmonic vibrational spectra can be calculated.[2]

[1] C. König and O. Christiansen, The Journal of Chemical Physics 145, 064105 (2016). [2] R. Haus et al. (2016) Icarus, 272, [2] D. Madsen, O. Christiansen and C. König, Phys. Chem. Chem. Phys. 20, 3445-3456 (2018).-205.

Posters


39

A new and efficient EOM-CCSD framework to model X-ray absorption spectroscopy Marta López Vidal1, Anna I. Krylov2, Sonia Coriani1

1Department of Chemistry, Technical University of Denmark, Kgs. Lyngby, Denmark 2Department of Chemistry, University of Southern California, Los Angeles, California,

United States.

X-ray absorption spectroscopy (XAS) is a powerful technique to obtain information on the geometric and electronic structure of atoms and molecules. The X-ray energy regime typically corresponds to the binding energy of core electrons, therefore the interaction between X-rays and matter results in excitation or ionization of core electron. Core-level binding energies being characteristic of a species, X-rays can be used to determine and characterize chemical substances [1]. However, to be able to thoroughly interpret experimental X-ray spectra, the spectra need to be compared to theoretical calculations. Indeed, computational studies are essential to assign the different features of the spectra and thus to extract the underlying electronic and structural information. Moreover, with the latest advances in the experimental side over the last years, in particular the free electron laser (FEL) and synchrotron installations, there has been a growing interest in the development of highly accurate theoretical methods for X-ray spectroscopy [2]. Time-dependent (TD) density functional theory (DFT) is undoubtedly the most used technique to model absorption spectra, mainly because of the relative low computational cost compared to more accurate ab initio methods. However, TDDFT often fails to give an accurate description of spectroscopic properties mostly due to the lack of a functional that can correctly describe core correlation and the so-called self-interaction error. There is thus an evident need for reliable wavefunction-based methods [3] to compute XAS spectra. These methods, although more expens ive, can be systematically improved, yielding thus to reliable results. Our work [4] is focused on the development of coupled cluster (CC) in the equation-of-motion (EOM) formalism, which is nowadays among the most accurate methods that can still be used with not too large molecules, but still rather limited when it comes to X-ray phenomena applications.

Simulated X-ray absorption spectrum of ethylene and ionization potential compared against experiment. [5]

[1] J. Stöhr, NEXAFS spectroscopy. Vol. 25. Springer Science & Business Media, 2013). [2] C.J. Milne, T.J. Penfold, M. Chergui, Coord. Chem. Rev. 277-278, 44-68 (2014). [3] T. Helgaker, S. Coriani, et al., Chem. Rev. 112, 54 (2012). [4] M. L. Vidal, X. Feng, E. Epifanovsky, A. I. Krylov and S. Coriani, "A new and efficient EOM-CCSD framework for core-excited states" (to be submitted to J. Chem. Theory Comput.) [5] Schirmer, J.; Trofimov, A.; Randall, K.; Feldhaus, J.; Bradshaw, A. M.; Ma, Y.; Chen, C. T.; Sette, F. Phys. Rev. A 1993, 47, 1136.

Posters


40

High-Resolution Synchrotron Terahertz Investigation of the Large-Amplitude Hydrogen Bond Librational Band of (HCN)2

D. Mihrin1, P. W. Jakobsen1, A. Voute1, L. Manceron2,3 and R. Wugt Larsen1

1 Department of Chemistry, Technical University of Denmark (DTU) Kemitorvet 206, DK2800 Kongens Lyngby

Tel.: +45 45252027, E-mail: [email protected]

2 Synchrotron SOLEIL L’Orme des Merisiers, Saint-Aubin-BP 48, 91192 Gif-sur-Yvette Cedex, France

3 Lab. MONARIS CNRS-UPMC UMR8233, 4 Place Jussieu, 75230 Paris Cedex, France

The high-resolution terahertz absorption spectrum of the large-amplitude intermolecular donor librational band ν1

8 of the homodimer (HCN)2 has been recorded by means of long-path static gas-phase Fourier transform spectroscopy at 207 K employing a highly brilliant electron storage ring source. The rovibrational structure of the ν1

8 band has the typical appearance of a perpendicular type band of a Σ–Π transition for a linear polyatomic molecule. The generated terahertz spectrum is analyzed employing a standard semi-rigid linear molecule Hamiltonian, yielding a band origin ν0 of 119.11526(60) cm−1 together with values for the excited state rotational constant B′, the excited state quartic centrifugal distortion constant DJ′ and the l-type doubling constant q for the degenerate state associated with the ν1

8 mode [1]. The until now missing donor librational band origin enables the determination of an accurate experimental value for the vibrational zero-point energy of 2.50 ± 0.05 kJ·mol−1 arising from the entire class of large-amplitude intermolecular modes. The spectroscopic findings are complemented by CCSD(T)-F12b/aug-cc-pV5Z (electronic energies) and CCSD(T)-F12b/aug-cc-pVQZ (force fields) electronic structure calculations, providing a (semi)-experimental value of 17.20 ± 0.20 kJ·mol−1 for the dissociation energy D0 of this strictly linear weak intermolecular CH⋯N hydrogen bond.

Fig. 1: The Q-branch of the ν1

8 librational band of the homodimer (HCN)2.

[1] Mihrin et al., Phys. Chem. Chem. Phys., 2018, 20, 8241-8246

Posters

Documents

02/,0 :* 0HHWLQJ %RRN RI $EVWUDFWV %RRN RI $EVWUDFWV · 02/,0 :* 0HHWLQJ %RRN RI $EVWUDFWV %RRN RI $EVWUDFWV ... wr