11th Nordic Femtochemistry Conference Vilnius – Lithuania

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11th Nordic Femtochemistry Conference Vilnius – Lithuania

May 26-27, 2014

Book of Abstracts

The NFC’14 organizing committee

Leonas Valkūnas Vidmantas Gulbinas

Ramūnas Augulis Renata Karpicz Olga Rancova

Vytenis Pranculis

Conference webpage: nordic2014.ftmc.lt

Conference email: [email protected]

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Center for Physical Sciences and Technology

Savanoriu ave. 231, LT-02300 Vilnius, LITHUANIA

Vilnius University

Universiteto 3, LT-01513 Vilnius, LITHUANIA

Lithuanian Physical Society

A. Goštauto 12, 01108 Vilnius, LITHUANIA ISBN 978-609-468-001-4

© Center for Physical Sciences and Technology, 2014 © Vilnius University, 2014

© Lithuanian Physical Society, 2014

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Conference programme MONDAY 26 MAY

09:00 OPENING CEREMONY

09:10 I1 MULTIDIMENSIONAL SPECTROSCOPY OF PHOTOREACTIVITY 11

Tobias Brixner

09:40 O1 3D SPECTROSCOPY OF QUANTUM DOTS 12

Joachim Seibt, Tonu Pullerits

10:00 O2 COHERENT DYNAMICS IN MUTATED PHOTOSYNTHETIC REACTION CENTER: INSIGHTS BY POLARIZATION RESOLVED 2D ELECTRONIC SPECTROSCOPY

12

David Paleček, Sebastian Westenhoff, Petra Edlund, Emil Gustavsson, Donatas Zigmantas

10:20 O3 DISORDER EFFECTS REVEALED IN MODELLED LH2 2DES SPECTRA 14

Olga Rancova, Darius Abramavicius

10:40 O4 EXCITON STRUCTURE OF BASEPLATE COMPLEX IN CHLOROSOMES REVEALED BY COHERENT 2D ELECTRONIC SPECTROSCOPY

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Jakub Dostal, František Vácha, Jakub Pšenčík, Donatas Zigmantas

11:00 COFFEE BREAK

11:30 I2 SPECTROSCOPY AND PICOSECOND DYNAMICS OF AQUEOUS NO2 16

Ane Riis Gadegaard, Jan Thøgersen, Svend Knak Jensen, Jakob Brun Nielsen, Naresh K. Jena2, Michael Odelius, Frank Jensen, Søren Rud Keiding

12:00 O5 DISTINCTION BETWEEN RELAXATION AND TRANSFER OF HOT ELECTRONS IN THE QUANTUM DOT-METAL OXIDE SYSTEMS

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Karel Žídek, Kaibo Zheng, Mohamed Abdellah, Tõnu Pullerits

12:20 O6 COHERENT CONTROL OF SUPERPOSITION OF ATOMIC RYDBERG STATES WITH FEMTOSECOND LASER PULSES

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Jana Preclíková, Martin Kozák, Daniel Fregenal, Bjørn Tore Hjertaker, Børge Hamre, Øyvind Frette, Ladislav Kocbach, Jan Petter Hansen

12:40 O7 VIBRATIONAL RELAXATION AND SOLVENT COUPLING IN METHYLATED XANTHINE DERIVATIVES

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Jakob Brun Nielsen, Jan Thøgersen, Svend Knak Jensen, Søren Rud Keiding

13:00 O8 FOUR WAVE MIXING SPECTROSCOPY AND MICROSCOPY OF INDIVIDUAL CARBON NANOTUBES

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Jukka Aumanen, Andreas Johansson, Olli Herranen, Pasi Myllyperkiö, Mika Pettersson

13:20 LUNCH

14:30 O9 FEMTOMAX – A NORDIC FACILITY FOR ULTRAFAST X-RAY SCIENCE AT THE MAX IV LABORATORY

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Andrius Jurgilaitis, Henrik Enquist, Matthias Burza, Maher Harb, Jesper Nygaard, Erik Wallén, Jörgen Larsson

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14:50 O10 ELECTRONIC STRUCTURE AND ULTRA-FAST SOLUTION DYNAMICS SEEN WITH X-RAY VISION THROUGH THEORETICAL SPECTACLES

22

Michael Odelius, Ida Josefsson

15:10 O11 MOLECULAR ELECTRON TRANSFER, SPIN CROSSOVER, SOLVATION AND THERMALIZATION DYNAMICS IN TRANSITION METAL CONTAINING SYSTEMS STUDIED WITH X-RAY FREE ELECTRON LASERS

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Kasper S. Kjær, Sophie E. Canton, Tim B. van Driel, Kristoffer Haldrup, Morten Christensen, Tobias Harlang, Pavel Chabera, Jens Uhlig2, Asmus O. Dohn, Klaus B. Møller, Jianxin Zhang, Yizhu Lui, Kenneth Wärnmark, Zoltan Nemeth, Amelie Bordage, György Vankó, Villy Sundström2, Martin M. Nielsen

15:30 O12 PROLONGING LIFETIMES OF METAL-TO-LIGAND CHARGE TRANSFER STATES IN IRON-BASED PHOTOSENSITIZERS

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T. Harlang, Y. Liu, P. Persson, V. Sundström, K. Wärnmark et al.

15:50 O13 PHOTOSTABILITY OF DISULFIDE BRIDGES 25

M. A. B. Larsen, A. B. Stephansen, L. B. Klein, T. I. Sølling

16:10 POSTER SESSION

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TUESDAY 27 MAY

09:00 I3 NEW DATA ON PHOTOSYNTHETIC LIGHT HARVESTING: IS IT SLOWER THAN THOUGHT BEFORE?

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Arvi Freiberg

09:30 O14 FLUORESCENCE LIFETIME OF CHLOROPHYLL A REVEALS REVERSIBLE PHOTO-PROTECTION MECHANISM IN THE GREEN ALGAE TETRASELMIS UNDER UV-STRESSED CONDITIONS

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Arne Kristoffersen, Svein Rune Erga, Børge Hamre, Øyvind Frette

09:50 O15 EXCITED STATE INTERACTIONS IN SIMPLE AMINES: TIME-RESOLVED GAS PHASE STUDIES 28

Liv B. Klein, James O. F. Thompson, Theis I. Sølling,Dave Townsend

10:10 O16 FLUCTUATING ANTENNA AS AN ORIGIN OF MULTI-EXPONENTIAL FLUORESCENCE KINETICS IN PHOTOSYSTEM II

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Jevgenij Chmeliov, Gediminas Trinkunas and Leonas Valkunas

10:30 O17 ULTRAFAST DYNAMICS IN PROTEINS EXPLORED USING THREE-PULSE TRANSIENT ABSORPTION SPECTROSCOPY

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Mikas Vengris, Vladislava Voiciuk, Donatas Zigmantas, Delmar S. Larsen

10:50 COFFEE BREAK

11:20 I4 TRACKING ENERGY FLOW THROUGH THE INTACT PHOTOSYNTHETIC APPARATUS 31

Jakub Dostál, Jakub Pšenčík, Donatas Zigmantas

11:50 O18 LIGHT-INDUCED FORMATION OF THE PFR STATE OF BACTERIOPHYTOCHROME FROM DEINOCOCCUS RADIODURANS

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Heli Lehtivuori, Heikki Takala, Pasi Myllyperki ö Chukharev Vladimir, Nikolai V. Tkachenko, Janne A. Ihalainen

12:10 O19 ENERGY TRANSFER PATHWAYS IN FUCOXANTHIN-CHLOROPHYLL PROTEIN COMPLEX REVEALED BY TWO DIMENSIONAL OPTICAL SPECTROSCOPY

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Andrius Gelžinis, Vytautas Butkus, Egidijus Songaila, Ramūnas Augulis, Andrew Gall, Claudia Buchel, Bruno Robert, Donatas Zigmantas, Darius Abramavicius, Leonas Valkunas

12:30 O20 POPULATION- AND COHERENT- DYNAMICS IN THE FENNA-MATTHEWS-OLSON COMPLEX CHARACTERIZED BY 2D ELECTRONIC SPECTROSCOPY

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Erling Thyrhaug, Karel Zidek, Jakub Dostal, and Donatas Zigmantas

12:50 O21 2D ELECTRONIC SPECTRA OF MARCUS ELECTRON TRANSFER 35

Thorsten Hansen

13:10 Lunch

14:00 I5 STUDIES OF ULTRAFAST PROTON/HYDROGEN TRANSFER PROCESSES 36

Jacek Waluk

14:30 O22 DIRECTED ENERGY TRANSFER IN FILMS OF CDSE QUANTUM DOTS 37

Kaibo Zheng, Karel Žídek, Mohamed Abdellah, Nan Zhu, Pavel Chábera, Nils Lenngren, Qijin Chi, Tõnu Pullerits

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14:50

O23 ULTRAFAST ELECTRONIC RELAXATION AND VIBRATIONAL COOLING DYNAMICS OF AU144(SC2H4PH)60 NANOCLUSTER PROBED BY TRANSIENT MID-IR SPECTROSCOPY

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Satu Mustalahti, Pasi Myllyperkiö, Tanja Lahtinen, Kirsi Salorinne, Sami Malola, Jaakko Koivisto, Hannu Häkkinen and Mika Pettersson

15:10 O24 CHARGE CARRIER RECOMBINATION IN S-DOPED INP NANOWIRES 39

Wei Zhang, Arkady Yartsev

15:30 O25 ON THE ROLE OF J-AGGREGATION IN STABILIZATION OF TRIPLET STATES IN NICKEL PHTALOCYANINE DERIVATIVE

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David Rais, Miroslav Menšík, Jiří Pfleger, Petr Toman, Jiří Černý

15:50 Coffee Break

16:20 O26 DISSOCIATION OF ELECTRON-HOLE PAIRS IN PLANAR HETEROJUNCTION ORGANIC SOLAR CELLS – ELECTROABSORPTION STUDY

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A. Devižis, J. De Jonghe, S. Jenatsch, R. Hany, F. Nüesch, V. Gulbinas and J.-E. Moser

16:40 O27 EXCITON-EXCITON ANNIHILATION IN METALLO-SUPRAMOLECULAR POLYMERS WITH ZN(II) ION-COUPLERS STUDIED BY PUMP-PROBE TRANSIENT ABSORPTION SPECTROSCOPY

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David Rais, Pavla Bláhová, Miroslav Menšík, Jan Svoboda, Jiří Vohlídal, Jiří Pfleger

17:00 O28 CHARGE CARRIER GENERATION AND TRANSPORT IN DIFFERENT STOICHIOMETRY APFO3:PC61BM SOLAR CELLS

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Vytenis Pranculis, Yingyot Infahsaeing, Zheng Tang, Andrius Devižis, Dimali Vithanage, Carlito Ponseca Jr., Olle Inganäs, Arkady Yartsev, Vidmantas Gulbinas and Villy Sundström

17:20 O29 NANOSTRUCTURE OF ORGANIC PHOTOVOLTAIC DEVICES REVEALED BY ULTRAFAST SPECTROSCOPY

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Almis Serbenta, Paul H. M. van Loosdrecht, Maxim S. Pshenichnikov

17:40 CLOSING CEREMONY

18:00 Conference dinner

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List of Poster presentations P1 PHOTO-PHYSICAL PROPERTIES OF HIGHLY ORDERED PSEUDOISOCYANINE FILMS AND

HETEROSTRUCTURES WITH [6,6]-PHENYL‑C61-BUTYRIC ACID METHYL ESTER 47

Oleksandr Boiko, Marius Franckevičius, Vytenis Pranculis, Vassili Nazarenko, Vidmantas Gulbinas

P2 EXCITATION DYNAMICS IN SINGLE-WALLED CARBON NANOTUBES WRAPPED WITH PFO-BPY.

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Angela Eckstein, Domantas Peckus, Vidmantas Gulbinias, Tomas Tamulevičius, Imge Namal, Tobias Hertel

P3 TIME-RESOLVED X-RAY DIFFRACTION STUDY OF THE PHONON DISPERSION IN INSB NANOWIRES.

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A. Jurgilaitis, H. Enquist, B. P. Andreasson, A. I. H. Persson, B.M. Borg, P. Caroff, K.A. Dick, M. Harb, H. Linke, R. Nüske, L. E. Wernersson, J. Larsson

P4 FLUORESCENCE PROPERTIES OF RHODAMINE 6G IN MESOSCOPIC MICELLE-SILICA MATRICES

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A. Kazakevičius1, V. Gulbinas1 and G.M. Telbiz

P5 ULTRAFAST CHARGE GENERATION, HIGH AND BALANCED CHARGE CARRIER MOBILITIES IN ORGANO HALIDE PEROVSKITE SOLAR CELL

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Carlito S. Ponseca Jr., Mohamed Abdellah, Kaibo Zheng, Arkady Yartsev, Tobjörn Pascher, Tobias Harlang, Pavel Chabera, Tonu Pullerits, Andrey Stepanov, Jean-Pierre Wolf, and Villy Sundström

P6 SURFACE PLASMON DYNAMICS IN CU CONTAINING AND AG CONTAINING DIAMOND LIKE CARBON NANOCOMPOSITE FILMS

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D. Peckus, T. Tamulevičius, Š. Meškinis, A. Tamulevičienė, A. Čiegis, A. Vasiliauskas, O. Ulčinas, S. Tamulevičius

P7 2D ELECTRONIC SPECTROSCOPY OF PORPHYRIN NANORINGS 53

Eglė Bašinskaitė, Jan Alster, Vytautas Butkus, Darius Abramavicius, Leonas Valkunas, Donatas Zigmantas

P8 SPECTRAL DYNAMICS IN QUENCHED LIGHT HARVESTING ANTENNA 54

Egidijus Songaila, Ramūnas Augulis, Erica Belgio, Alexander Ruban, Leonas Valkūnas

P9 EXPLORING FIRST PRINCIPLE METHODS FOR STUDYING N,N-DIMETHYLAMINOBENZYLIDENE-1,3-INDANDIONE EXCITED STATES.

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Guntars Zvejnieks, Martins Rutkis and Andrejs Jurgis

P10 UNUSUAL 2D ELECTRONIC SPECTROSCOPY SIGNALS FROM PERIDININ CHLOROPHYLL A PROTEIN.

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J. Alster, S. Yoo, D. Zigmantas

P11 FEMTOSECOND TIME-RESOLVED GAS PHASE STUDIES OF THE CIS- AND TRANS-AZOBENZENE RADICAL CATIONS.

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Kristin Munkerup, Timothy Bohinski, Maryam Tarazkar, Katharine M. Tibbetts, Theis I. Sølling and Robert J. Levis

P12 OPTICALLY CONTROLLED BIDIRECTIONAL SWITCHING OF AN INDOLOBENZOXAZINE TYPE PHOTOCHROMIC COMPOUND Kipras Redeckas, Vladislava Voiciuk, Rasa Steponavičiūtė, Vytas Martynaitis, Algirdas Šačkus, and Mikas Vengris

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P13 RAMAN AND ELECTRONIC ABSORPTION SPECTRA IN CAROTENOIDS: A DENSITY FUNCTIONAL THEORY STUDY

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Mindaugas Macernis

P14 CHARGE SEPARATION PATHWAYS IN DYE/FULLERENE BULK-HETEROJUNCTION SOLAR CELLS

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Ramūnas Augulis, Domantas Peckus, Andrius Devižis, Dirk Hertel, Vidmantas Gulbinas

P15 STUDY OF ARTIFICIAL LIGHT HARVESTING ANTENNAE BY QUANTUM CHEMICAL METHODS 61

Svetlana Malickaja, Mindaugas Macernis, Juozas Sulskus, Leonas Valkunas

P16 ELECTRONIC PROPERTIES OF INDOLO[3,2-B]CARBAZOLE COMPOUNDS REVEALED BY TIME RESOLVED SPECTROSCOPY

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Simona Streckaitė, Renata Karpicz, Alytis Gruodis, Saulius Grigalevičius

P17 HIGHLY EFFICIENT INTRINSIC PHOSPHORESCENCE FROM A Σ-CONJUGATED POLY(SILYLENE) POLYMER

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S. Toliautas, J. Sulskus, A. Kadashchuk, Yu. Skryshevski, A. Vakhnin, R. Augulis, V. Gulbinas, S. Nespurek, J. Genoe, and L. Valkunas

P18 MODELING OF EXCITATION TRANSFER DYNAMICS IN THE PHOTOSYNTHETIC FMO COMPLEX USING THE STOCHASTIC SCHRÖDINGER EQUATION.

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Vytautas Abramavicius, Darius Abramavicius

P19 VIBRATIONAL RELAXATION WITHIN THE CAROTENOID S1 STATE VIA HIGH FREQUENCY MODES.

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Vytautas Balevičius Jr., Leonas Valkunas and Darius Abramavicius

P20 DYNAMICS OF EXCITONIC POLARON FORMATION IN MOLECULAR ASSEMBLIES 66

Vladimir Chorošajev, Darius Abramavicius

P21 ELABORATING THE EXCITED STATE DYNAMICS OF THE PERIDININ-CHLOROPHYLL-A PROTEIN

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Vladislava Voiciuk, Kipras Redeckas, Donatas Zigmantas and Mikas Vengris

P22 TAILING SURFACE TRAPS IN SN-DOPED INP NANOWIRES 68


P23 ELECTRON DYNAMICS IN PHOTO-EXCITED SODIUM IODIDE IN THE GAS PHASE 69

Torsten Leitner, Franziska Buchner, Andrea Luebcke, Arnaud Rouzée, Linnea Rading, Per Johnsson, Michael Odelius, Hans Karlsson, Marc Vrakking, Philippe Wernet

P24 FROM ULTRAFAST EVENTS TO EQUILIBRIUM – UNCOVERING THE UNUSUAL DYNAMICS OF ESIPT REACTION: THE CASE OF DUALLY FLUORESCENT DIETHYL-2,5-(DIBENZOXAZOLYL)-HYDROQUINONE. Paweł Wnuk, Gotard Burdziński, Michel Sliwa, Michał Kijak, Anna Grabowska, Jerzy Sepioła, Jacek Kubicki

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P25 ULTRAFAST TRIR AND FLUORESCENCE MEASUREMENTS OF EXCITED STATE PROTON TRANSFER IN ANILS Piotr Skibiński, Paweł Wnuk, Jacek Waluk and Czesław Radzewicz

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P26 ENERGY TRANSFER IN PLANT LIGHT-HARVESTING COMPLEX II REVEALED BY ROOM-TEMPERATURE 2D ELECTRONIC SPECTROSCOPY Petar H. Lambrev, Kym Wells, Zhengyang Zhang, Győző Garab, Howe-Siang Tan

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P27 BIMOLECULAR PHOTOINDUCED ELECTRON TRANSFER BEYOND THE DIFFUSION LIMIT: THE REHM-WELLER EXPERIMENT REVISITED WITH FEMTOSECOND TIME-RESOLUTION Arnulf Rosspeintner, Gonzalo Angulo, Eric Vauthey

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Oral presentations

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I1 Multidimensional spectroscopy of photoreactivity

Tobias Brixner1

1Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

Email: [email protected]

Coherent two-dimensional (2D) spectroscopy has become a valuable tool for investigating energy transfer in multichromophore systems, especially in biological light harvesting. We recently also studied artificial systems such as carbazole dendrimers [1].

In the literature, application of electronic 2D spectroscopy has been limited to photophysical processes in which the investigated system returns to the initial state after the pulse sequence is over and the photoinitiated dynamics are complete. By contrast, the emphasis of this talk is on photochemical processes in which permanent changes in the molecular structure occur. In a merocyanine system, we conclude from the presence of a “cross peak” linking reactant and product that a particular reaction channel occurs. Recording a sequence of 2D spectra, an additional Fourier transformation along population time T reveals information about the reaction coordinate (3D spectroscopy). The 3D peaks (Fig. 1) can be associated with vibrations that are decisive for the photochemical reaction from the TTC (red) to the TTT isomer (blue) [2].

With a chemically modified molecule for which the reaction is not allowed, the disappearance of the cross peak proves that the channel is closed [3]. Going one step further, one can study whether photochemical reactions are accessible via higher-lying electronic states. In this case, an additional “trigger” pulse is employed in fifth-order triggered-exchange 2D spectroscopy [4]. Finally, coherent control using shaped laser pulses on the same molecule provides additional information on the propagation of the prepared wave packet.

REFERENCES [1] I. Hwang, U. Selig, S. S. Y. Chen, P. E. Shaw, T. Brixner, P. L. Burn, and G. D. Scholes; J. Phys. Chem. A 117 (2013) pp. 6270-6278. [2] S. Ruetzel, M. Diekmann, P. Nuernberger, C. Walter, B. Engels, and T. Brixner; PNAS (2014) DOI 10.1073/pnas.1323792111. [3] M. Kullmann, S. Ruetzel, J. Buback, P. Nuernberger, and T. Brixner; J. Am. Chem. Soc. 133 (2011) pp. 13074-13080. [4] S. Ruetzel, M. Kullmann, J. Buback, P. Nuernberger, and T. Brixner; Phys. Rev. Lett. 110 (2013) pp. 148305.

Fig. 1. Coherent 3D spectroscopy on a photochemically reactive system [2].

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O1 3D Spectroscopy of Quantum Dots

Joachim Seibt1 and Tonu Pullerits1 1Department of Chemical Physics, Lund University, Box 124, SE-21000,Lund, Sweden


In 2D electronic spectroscopy, oscillatory signals have recently received increased attention. The key issue is the origin of such beating - whether it is vibrational or electronic. In analogy to the distinction between rephasing and nonrephasing contributions to 2D spectra, we separate signal components with positive and negative coherence beating frequency via a third Fourier transformation and consider two-dimensional cuts at the respective positions. We apply this approach to a model system for the description of quantum dots (QDs) and analyze the possibility to distinguish between vibrational effects associated with the longitudinal optical (LO) phonon mode and electronic fine structure splitting [1]. The analysis of Feynman diagrams with evolution in a coherence with positive or negative beating frequency during the population time interval allows to predict peak positions. However, in the model with vibrations the second-order cumulant expansion approach lead to effects which are not captured by a Feynman diagram description. Due to the influence of inhomogeneous broadening, in the case of rephasing contributions constructive superposition effects appear, which result in elongated peaks. Under our model assumption that the vibrational frequency depends on the QD size dependent shift of the electronic excitation energies of singly and doubly excited state, the elongated peaks of all rephasing contributions exhibit a tilt. In our study the question is addressed whether the model assumption of a splitting of the singly excited states in terms of fine structure levels instead of a vibrational substructure would lead to different findings. Thereby we assume that the respective coherence beating frequency depends on the electronic excitation energy shift via a common particle size dependence, as in the case of vibrational effects. It turns out that under this assumption elongated peak structures from inhomogeneous broadening effects are still obtained by taking a Debye spectral density contribution into account in the respective calculation, but that then the tilt effect is much less pronounced than under the model assumption of an additional Lorentzian spectral density component. Thus, the extent of the tilt effect under the influence of inhomogeneous broadening can be identified as a quantitative criterion for the distinction between vibrational and electronic coherences in our QD model system. The proposed tilt effect in two-dimensional cuts of 3D spectra can also appear in other systems than QDs under the conditions that inhomogeneous broadening effects outweigh homogeneous broadening and that a coherence evolution during the population time interval is influenced by inhomogeneous broadening effects.

REFERNCES [1] J. Seibt and T. Pullerits, J. Phys. Chem. C, 117 (2013) pp. 18728-18737.

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O2 Coherent Dynamics in Mutated Photosynthetic Reaction Center: Insights by Polarization Resolved 2D Electronic

Spectroscopy

David Paleček1,3, Sebastian Westenhoff2, Petra Edlund2, Emil Gustavsson2 and Donatas Zigmantas1

1Department of chemical physics, Lund University, P.O. Box 124, SE-22100 Lund, Sweden. 2Department of Chemistry, Biochemistry and Biophysics, University of Gothenburg, Box 462, SE-

40530 Göteborg, Sweden. 3Department of chemical physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech

Republic. Email: [email protected]

The photosynthetic reaction center is one of the fundamental components in photosynthetic light-harvesting machinery, being responsible for charge separation and subsequent electron transfer across the photosynthetic membrane. The resulting photogenerated transmembrane potential is used to synthesize energy rich products which drive almost all biochemical processes.

Earlier studies have shown long-lived coherent beatings in the bacterial reaction center (bRC) of the purple bacterium Rhodobacter sphaeroides. These beatings have been assigned to vibrational and mixed vibronic coherence with substantial electronic character [1,2]. To further elucidate the possible biological relevance of the observed quantum coherence, we apply polarization resolved 2D electronic spectroscopy to compare excitation energy transfer and coherent dynamics in the native bRC and in mutants with specifically altered residues. These residues (M210, L104 and L100, where the letter denotes the protein subunit and number is the residue position in the peptide chain) are in close proximity to the pigments in the electron transport active branch of the cofactor structure of the bRC, and are individually mutated.

The electron transport is known to be up to 50 times slower in the mutated bRCs, but at the time-scales so far investigated [3] the energy transfer rate is seemingly unchanged. In our study we use chemically oxidized bRCs to prevent charge separation from the special pair, which allows us to focus solely on the energy transfer and alternative charge separation pathways not involving the special pair [4].

REFERENCES [1] S. Westenhoff, D. Paleček, P. Edlund and D. Zigmantas; JACS 8 (2001) pp. 520-531. [2] I.S. Ryu, H. Dong and G.R. Fleming; J Phys Chem B 118 (2014) pp. 1381-1388. [3] M.E. van Brederode et al.; Photosynth Res 55 (1998) pp. 141-146. [4] ME. van Brederode et al.; PNAS 96 (1999) pp. 2054-2059.

Fig.1: Cofactor structure of bRC with highlighted M210 tyrosine residue mutated to phenylalanin (green).

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O3 Disorder effects revealed in modeled LH2 2DES spectra

Olga Rancova and Darius Abramavicius

Department of Theoretical Physics, Vilnius University, Sauletekio av. 9, Vilnius, Lithuania. Email: [email protected]

Two dimensional coherent electronic spectroscopy (2DES) can help to directly distinguish between contributions of different parameters, such as the width of the static disorder and the homogeneous linewidth, on the resulting spectra obscured in the linear absorption since both contribute to the spectral linewidth.

The object of this research is a peripheral light-harvesting complex LH2 of purple bacteria. 2DES rephasing technique has been applied to measure LH2 (Rdb. sphaeroides species) spectra at room temperature [1] and earlier of the spectral variant of the LH2 complex (B800-820) of Rps. acidophila strain 7050 at 77 K [2].

Using an excitonic model of a double-ring LH2 aggregate we perform simulations of its 2DES spectra [3] and find that the model of a harmonic environment cannot provide a consistent set of parameters for two, 77 K and room, temperatures simultaneously (Fig. 1). This indicates highly anharmonic nature of protein fluctuations for the pigments of B850 ring.

We have performed analysis of the static and dynamic disorder of the exciton model for the LH2 aggregate. We find the whole range of the correlated parameters of the static and dynamic disorder suitable to model proper absorption spectrum. However different sets of parameters are needed to simulate 2DES at different temperatures. We find that the disorder parameters must carry temperature dependence so that the spectra become much more homogeneous at room temperature compared to the 77 K temperature.

REFERENCES [1] A. F. Fidler et.al., Nat. Commun. 5 (2014) 3286. [2] D. Zigmantas et.al., Proc. Nat. Acad. Sci. 103 (2006) 12672–12677. [3] D. Abramavicius et.al., Chem Rev. 109 (2009) 2350–2408.

Fig. 1 Simulated 2DES (real part) of LH2 at two temperatures with a same

set of parameters

w1, 104 cm−1

w3, 1

04 cm

−1

−1.30−1.25−1.20−1.15−1.101.10

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w1, 104 cm−1

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O4 Exciton structure of baseplate complex in chlorosomes

revealed by coherent 2D electronic spectroscopy

Jakub Dostál1,2, František Vácha3, Jakub Pšenčík2 and Donatas Zigmantas1

1Department of Chemical Physics, Lund University, P.O.Box 124, 221 00 Lund, Sweden. 2Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague,

Czech Republic. 3Faculty of Science, University of South Bohemia, Branišovská 31, 370 05, České Budějovice, Czech

Republic. Email: [email protected].

Chlorosomes are the light-harvesting antennas found in representatives of green photosynthetic bacteria. The vast majority of their pigment content is gathered in the self-assembled aggregate structure that is responsible for the photon capturing events. In contrast to this architecture, the bacteriochlorophyll (BChl) a molecules in the chlorosome are organized into the baseplate pigment-proteins complex forming the two-dimensional structure attached to the side of the chlorosome facing the cytoplasmic membrane (for review see [1]). Its function is the excitation energy transfer from the chlorosomal aggregate towards the reaction centre. Although the structure of the main baseplate constituent - the BChl a binding CsmA protein - has been determined by means of liquid state NMR, the exact arrangement of the CsmA units in the baseplate is not known, including the information about relative orientation and distances between the individual BChl a molecules.

We have studied the energetic structure of the baseplate in chlorosomes from the green sulfur bacterium Chlorobaculum tepidum at 77 K by means of the coherent two-dimensional electronic spectroscopy (2DES). This method provides simultaneously high spectral and temporal resolution. The experiments revealed that the baseplate absorption at 77 K covers spectral region between approximately 790 and 830 nm, and exhibits rather complicated exciton structure consisting of apparently four levels. The strong correlation between the individual exciton levels is apparent from the presence of cross-peaks located above the diagonal in the 2D spectrum measured at early population times. The energy transfer from the chlorosome aggregate to the baseplate and energy relaxation inside the baseplate was observed on the time scale of tens to hundreds of picoseconds

REFERNCES [1] Pedersen MØ et al.; Photosynth. Res. 104 (2010) pp. 233-243.

Illustration of 2DES experiment on

chlorosomes showing the experimental 2D spectrum at 30 fs after excitation composed from the

aggregate and the baseplate complex signals

16

I2 Spectroscopy and picosecond dynamics of aqueous NO2

Ane Riis Gadegaard1, Jan Thøgersen1, Svend Knak Jensen1, Jakob Brun Nielsen1, Naresh K. Jena2, Michael Odelius2, Frank Jensen1, and Søren Rud Keiding1

1 Department of Chemistry, Aarhus University, Langelandsgade 140, DK 8000 Aarhus C, Denmark 2 Department of Physics, Albanova University Center, Stockholm University, S-106 91 Stockholm,

Sweden Email: [email protected]

We investigate the spectroscopy and dynamics of aqueous nitrogen dioxide, 푁푂 (푎푞) formed through femtosecond photolysis of nitrate, 푁푂 (푎푞) and nitromethane 퐶퐻 푁푂 (푎푞). The formation of photoproducts is monitored using infrared transient absorption with femtosecond time resolution. Common to all the experiments is the observation of a strong induced absorption at 1610±10 cm-1, that we assign to the asymmetric stretch vibration in the electronic ground state of 푁푂 (푎푞). This assignment is substantiated through isotope experiments substituting 14N by 15N, experiments at different pH values, and by theoretical calculations and simulations of 푁푂 − 퐷 푂 clusters. In experiments utilizing 200 nm photolysis pulses, the spectral signature of 푁푂 (푎푞) rises slowly with an appearance time of approximately 31 picoseconds. The slow appearance time is caused by the initial population and subsequent depopulation of the excited 2B2 state in 푁푂 (푎푞) following the photolysis of both parent molecules. A theoretical investigation of the excited states in 푁푂 and Car-Parrinello molecular dynamics simulations of the hydration structures of 푁푂 facilitates the interpretation of the experimental data and, in addition, provides a detailed description of the photochemistry of aqueous 푁푂 . In spite of the omnipresence of nitrogen dioxide in both atmospheric and aqueous chemistry, it has remained surprisingly elusive when it comes to direct observations in the aqueous phase. We believe this is the first direct observation of the infrared signatures of aqueous 푁푂 .

17

O5 Distinction between relaxation and transfer of hot electrons

in the quantum dot-metal oxide systems

Karel Žídek1, Kaibo Zheng1, Mohamed Abdellah1 and Tõnu Pullerits1

1Department of Chemical Physics, Lund University, Getingevägen 60, 22241 Lund, Sweden.

Email: [email protected].

Performance of the solar cells based on quantum dots (QDs) has been rapidly improving during the last years. The wave of interest has been mainly motivated by the vision of multiple exciton generation and collection[1-2]. However, QDs offer another possibility to exploit light energy efficiently by using the so-called hot electron transfer [3-4]. Here an electron is injected into a suitable acceptor (e.g. metal oxide) before losing all its excess energy due to thermal relaxation.

Although the “cold” electron injection from QD to MO has been studied to a big detail [1-3], the hot electron injection has been subject of only a few studies with controversial results [3-4]. Firstly, it involves fast processes on the sub-picosecond timescale; secondly, the commonly-used spectroscopic techniques offer only indirect evidence of the injection.

In our contribution we will present a systematic study demonstrating how to distinguish between hot electron transfer from QDs and a simple change in electron relaxation. We have carried out a set of measurements of the initial transient absorption dynamics for three different systems of QDs: QDs in solution, agglomerated QDs on silica, and QD-ZnO.

Our measurements reveal a rapid speeding-up of relaxation dynamics (by ~ 3 ps-1), when QDs are attached to ZnO (see Fig. 1). Such behavior could be misinterpreted as a hot electron transfer. However the detail analysis of the transient absorption dynamics and amplitudes reveals that this effect is not connected to the electron injection at all.

The analysis therefore provides a systematic tool to distinguish hot electron transfer from changes in electron relaxation, while employing a commonly-used ultrafast spectroscopic technique. Moreover, the analysis can be used for any QD-based donor-acceptor system.

REFERENCES

[1] K. Žídek, K. Zheng, M. Abdellah, N. Lengrenn, P. Chábera, and T. Pullerits Nano Lett. 12 (2012) pp. 6393. [2] K. Žídek, K. Zheng, C. S. Ponseca Jr., M. E. Messing, L. R. Wallenberg, P. Chábera, M. Abdellah, V. Sundström, and T. Pullerits J. Am. Chem. Soc. 134 (2012) pp. 12110. [3] K. Tvrdy, P.A. Frantsuzov, P. V. Kamat, Proc. Natl. Acad. Sci. U.S.A. 108, (2010) pp. 29. [4] W.A. Tisdale, K. J. Williams, A.T. Brooke, D.J. Norris, S. A. Eray, X-Y Zhu Science 328 (2010) pp. 1543.

Fig.1 Onset rate of the 1Se state bleach under various exc. energies for QDs in solution (black squares), QD-SiO2 (blue triangles), and QD-ZnO (red circles). Inset: example of measured kinetics (exc.3.18 eV).

0.0 0.3 0.6 0.9 1.20

3

6

9

0.0 0.5

-1

0

QD

QD-SiO2

onse

t rate

(ps-1

)

excess energy (eV)

QD-ZnO

2.2 2.4 2.6 2.8 3.0 3.2excitation photon energy (eV)

ab

s.

delay (ps)

18

O6 Coherent control of superposition of atomic Rydberg states

with femtosecond laser pulses

Jana Preclíková1, Martin Kozák2, Daniel Fregenal3, Bjørn Tore Hjertaker1, Børge Hamre1, Øyvind Frette1, Ladislav Kocbach1, Jan Petter Hansen1

1Department of Physics and Technology, University of Bergen, N-5007 Bergen, Norway

2Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2, Czech Republic

3Centro Atómico Bariloche and Consejo Nacional de Investigaciones Cientícas y Técnicas. R8402AGP S.C. de Bariloche, Argentina


We report on experimental and theoretical studies of interaction of Rydberg atoms with sequences of gaussian femtosecond laser pulses in collinear and double-grating arrangements. Sequences of pairs of laser pulses allow the control of the phase between each excited state in a coherent superposition of Rydberg wave packet. Experimentally, we studied populating of the atomic Rydberg states after interaction with a pair of identical femtosecond laser pulses, with a pair of pulses in which one of the pulse was strongly chirped and with two pairs of femtosecond laser pulses. Evolution of superpositions of 20f-30f states of lithium atoms was determined by the selective field ionisation (SFI) method as a function of the time delay between the femtosecond laser pulses and pulse pairs. All our observed results are in excellent agreement with theoretical calculations given by the first order perturbation theory [1,2].

We demonstrate that an excitation of a selected Rydberg state on picosecond timescale can be reached by a pure sequence of four pairs of femtosecond laser pulses with precisely set delays [2]. We proposed a method for characterizing of thermal beam velocity based on observing of Ramsey fringes in double-grating pump and probe setup, see Fig. 1 [3].

REFERENCES [1] J. Preclíková, M. Kozák, D. Fregenal, Ø. Frette, B. Hamre, B. T. Hjertaker, J. P. Hansen, and L. Kocbach, Phys. Rev. A 86, 063418 (2012). [2] M. Kozák, J. Preclíková, D. Fregenal, and J. P. Hansen, Phys. Rev. A 87, 043421 (2013). [3] J. Preclíková, M. Kozák, D. Fregenal, and J. P. Hansen, Phys. Rev. A ??, accepted (2014).

Fig. 1 Map of amplitudes of Ramsey fringes oscillations as function of time delay between

pump and probe intensity gratings and position x0 for thermal beam

with gaussian distribution of velocities [3].

19

O7 Vibrational relaxation and solvent coupling in methylated

xanthine derivatives Jakob Brun Nielsen1, Jan Thøgersen1, Svend Knak Jensen1 and Søren Rud Keiding1

Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Århus C


Under harsh UV radiation in the environment of the prebiotic world, the present day nucleobases endured natural selection to become the code of life, whereas multiple other nucleobases failed. Xanthine and its methylated derivatives is one such example [1].

A series of xanthine derivatives, which share excited state characteristics with the canonical DNA bases[2], is dissolved in D2O and irradiated with 266 nm laser pulses. A strong ππ* transition is induced. The electronic excited state decays via a conical intersection with the electronic ground state in less than a picosecond, and the electronic excitation energy is converted to vibrational energy on the electronic ground state surface, abruptly upsetting thermal equilibrium (TE). The subsequent return to TE is monitored with infrared pulses ranging from 1550 to 1730 cm-

1 in a transient absorption experiment. The aim of this study is to reveal the nature and mechanism behind vibrational relaxation in a series of closely related molecules. Changing the degree of methyl substitution in the xanthine derivatives changes the nature of the solute to solvent coupling, thus influencing the rate of VC. We find TE recovery lifetimes ranging from 2.2 ps in 7-methylxanthine (7-MX) to 5.5 ps in 1,3,7-trimethylxanthine (1,3,7-TMX).

REFERENCES:

[1] Callahan et al., PNAS, 2011, vol. 108

no. 34, 13995–13998

[2] Zhang et al., J. Phys. Chem. A, 2013, 117, 6771−6780

Fig. 1 Transient absorption of 1,3,7-trimethylxanthine

1560 1580 1600 1620 1640 1660 1680 1700 1720-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

Wavenumbers [cm-1]

A [m

OD

]

1,3,7-TMX

inv. FTIRt<0 ps1,1 ps1,9 ps3,3 ps4,8 ps8 ps16 ps30 ps

Fig 2 Kinetic trace of 1,3,7-trimethylxanthine and 7-methylxanthine following 266 nm

0 5 10 15

-1

-0.8

-0.6

-0.4

-0.2

0

t [ps]

A, n

orm

.

1,3,7-TMX7-MX

20

O8 Four wave mixing spectroscopy and microscopy of individual

carbon nanotubes

Jukka Aumanen1, Andreas Johansson2, Olli Herranen2, Pasi Myllyperkiö1, Mika Pettersson1

1Nanoscience Center, Department of Chemistry, University of Jyväskylä, Finland 2Nanoscience Center, Department of Physics, University of Jyväskylä, Finland


The properties of single walled carbon nanotubes (SWCNT) depend strongly on their size and structure. However, currently there are no synthesis methods that could produce homodisperse carbon nanotube samples complicating the studies of the structure-dependent properties. The problem can be overcome by carrying out experiments for individual nanotubes. It is generally known that Raman spectroscopy and fluorescence measurements can be performed for individual SWCNTs. Moreover, the large non-linear response of the SWCNTs allows us to carry out femtosecond four wave mixing (FWM) experiments for the individual nanotubes.

We have combined femtosecond laser pulses and microscope optics in order to achieve high spatial and temporal resolution and sufficient light intensity to obtain response from individual SWCNTs. The investigated SWCNTs are grown over a slit that allows laser beams to pass through the sample. With this sample geometry when FWM signal is collected in backscattering direction the method is practically free of background scattering.

In Figure 1 FWM image is presented together with a transmission electron microscope (TEM) image of the same sample. FWM method can be applied as a non-destructive imaging and characterization method for individual SWCNTs. However under continuous excitation and in the presence of oxygen the FWM signal decreases gradually due to photo-induced oxidation. Electron microscopy studies reveal that although FWM signal is lost the nanotube is still not removed in oxidation process.

The deeper understanding of the structure dependent properties of SWCNTs, including non-linear optical response, is expected to be valuable for development of advanced applications. In the future, femtosecond FWM method may appear to be an important tool also in the studies of various other nanomaterials.

Fig. 1 FWM (left) and TEM (right)

images showing suspended SWCNTs crossing a slit

21

O9 FemtoMAX – a Nordic facility for ultrafast X-ray science at

the MAX IV laboratory.

Andrius Jurgilaitis1.2, Henrik Enquist2, Matthias Burza2, Maher Harb1,2, Jesper Nygaard2, Erik Wallén2 and Jörgen Larsson1,2

1Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden. 2 MAX IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden.


Ultrafast laser pump and X-ray probe experiments can presently be carried out at free-electron lasers. Presently, LCLS in USA and SACLA in Japan are in operation and in 2016 the European X-FEL in Hamburg will open. The MAX IV storage ring will be innaugurated in July 2016. This 3 GeV storage ring has a full energy linear accelarator (LINAC) as injector of electrons. This linear accelerator can produce short pulses and will be used as the driver for the FemtoMAX beamline [1]. FemtoMAX is optimized to perform time resolved X-ray studies with femtosecond resolution at wavelengths matching interatomic distances. Short electron pulses from the MAXIV LINAC entering the FemtoMAX undulator will produce bright X-rays (>1e7 per bunch below 10 keV) which is going to be used for time resolved x-ray studies. The FemtoMAX beamline is equipped with a state-of-the-art ultrafast laser system with wide tunability. Other parts include in-house developed lab equipment, X-ray beam diagnostics, experiental stations and detectors. All this will make FemtoMAX a very actractive place for time resolved X-ray experiments.

In this presentation a status of the FemtoMAX beamline and MAX IV facility will be presented. A time plan and key beamline specifications will be shown.

Fig. 1 Overview of the MAX-IV Short Pulse Facility.

REFERNCES [1] S. Werin, S. Thorin, M. Eriksson and J. Larsson, Nuclear Instruments and Methods in Physics Research A, 601, (2009), 98-107.

22

O10 Electronic structure and ultra-fast solution dynamics seen

with X-ray vision through theoretical spectacles Michael Odelius1 and Ida Josefsson1

1Department of Physics, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden

Email: [email protected] In this paper, X-ray studies of ultra-fast dynamics and

electronic structure in solution is presented from a theoretical perspective. In particular, the combination of multi-configura-tional post-Hartree-Fock calculations and L-edge Resonant Inelastic X-ray Scattering (RIXS) spectroscopy is put forward as a powerful probe of the valence electronic structure in transition metal complexes. By core-excitations targeting a particular element in a complicated system, the local character of valence-excited final states can be probed by measuring state-specific fluorescence decay pathways.

After photo-excitation with UV photons of Fe(CO)5 in ethanol solution, transient electronic states and reaction intermediates are identified in time-resolved Fe L-edge RIXS [1]. Solute-solvent interactions are shown to influence the reaction path-way on a sub-ps time-scale. Furthermore, with similar techniques, simulations of measured data from core-level photo-electron spectroscopy have been used to investigate hydrogen-bond dynamics for I3-(aq) [5] and time-resolved studies in photo-dissociation in gas phase [6].

The theoretical framework of the multi-configurational restricted active space self-consistent field (RASSCF) method is introduced in the context of X-ray spectroscopy in applications to aqueous solutions [2-4]. Ab initio molecular dynamics (AIMD) simulations is an established tool for modeling solution dynamics giving an accurate description of solute-solvent interactions. The prospect of combining AIMD with RASSCF calculations for sampling of ground state dynamics and photo-induced processes is discussed.

REFERENCES [1] Ph. Wernet, K. Kunnus, I. Josefsson, I. Rajkovic, W. Quevedo, M. Beye, S. Schreck, S. Grübel, M. Scholz, D. Nordlund, W. Zhang, R. W. Hartsock, W. F. Schlotter, J. J. Turner, B. Kennedy, F. Hennies, F. M. F. de Groot, K. J. Gaffney, S. Techert, M. Odelius, and A. Föhlisch. Unpub (2014) [2] I. Josefsson, K. Kunnus, S. Schreck, A. Föhlisch, F. de Groot, Ph.Wernet, and M. Odelius, J. Phys. Chem. Lett., 3 (2012) pp 3565–3570. [3] Ph. Wernet, K. Kunnus, S. Schreck, W. Quevedo, R. Kurian, S. Techert, F. de Groot, M. Odelius, and A. Föhlisch, J. Phys. Chem. Lett. 3 (2012) pp. 3448–3453. [4] K. Kunnus, I. Josefsson, S. Schreck, W. Quevedo, P. Miedema, P. Miedema, S. Techert, F. de Groot, A. Föhlisch, M. Odelius, and Ph. Wernet, Unpub (2014) [5] I. Josefsson, S. K. Eriksson, N. Ottosson, G. Öhrwall, H. Siegbahn, A. Hagfeldt, H. Rensmo, O. Björneholm, and M. Odelius, Phys. Chem. Chem. Phys. 15 (2013) pp 20189–20196. [6] Ph. Wernet, M. Odelius, K. Godehusen, J. Gaudin, O. Schwarzkopf, and W. Eberhardt, Phys. Rev. Lett. 103 (2009) pp 013001.

23

O11

Molecular electron transfer, spin crossover, solvation and thermalization dynamics in transition metal containing

systems studied with X-ray Free Electron Lasers.

Kasper S. Kjær1,2, Sophie E. Canton3, Tim B. van Driel1, Kristoffer Haldrup 1, Morten Christensen1, Tobias Harlang2, Pavel Chabera2, Jens Uhlig2, Asmus O. Dohn4, Klaus B.

Møller4, Jianxin Zhang5, Yizhu Lui5, Kenneth Wärnmark5, Zoltan Nemeth6, Amelie Bordage6, György Vankó6, Villy Sundström2, Martin M. Nielsen1

1Centre for Molecular Movies, Danish Technical University, Physics Department, 2800, Lyngby, Denmark 2Chemical Physics Department, Lund University, PO Box 118, 22100 Lund, Sweden

3Department of Synchrotron Radiation Instrumentation, Lund University, PO Box 118, 22100 Lund, Sweden 4Department of Chemistry, Danish Technical University, Physics Department, 2800, Lyngby, Denmark

5Centre for Analysis and Synthesis, Lund University, PO Box 118, 22100 Lund, Sweden 6Wigner Research Centre for Physics, Hungarian Academy Sciences, 1525 Budapest, P.B. 49, Hungary

This presentation will show results from some of the first combined time-resolved X-ray Scattering and X-ray Emission Spectroscopy measurements conducted at the two operational Hard X-ray Free Electron Laser sources. The studies have focused on elucidating the relationship between electronic kinetics and molecular structural dynamics during electron transfer and spin-relaxation processes in both bimetallic photocatalytic model complexes and in a set of iron containing spin-crossover systems in solution.

The combination of the X-ray emission and transient optical absorption spectroscopy allow us to map the details of the electron transfer and spin relaxation pathways with femtosecond time-resolution. The simultaneously measured X-ray scattering data show how these processes drive large structural changes of the molecular species. Furthermore the scattering data is shown to provide a handle on solvent-solute interactions, flow of excess excitation energy and solvent dynamics, during the first few picoseconds after the excitation event. An example of the information extracted from these combined measurements is given in Figure 1, for the case of the bimetallic photocatalytic model compound.

Fig. 1: Excited state cascade of a bimetallic ruthenium-cobalt system. MLCT excitation of the ruthenium centre induces electron transfer to the

cobalt moiety via the aromatic bridge with a 240 fs time-constant. The electron transfer to the cobalt site

induces a spin-state transition with a 1.9 ps time-constant, driving a 0.2 Å elongation of the Co-N

bonds. The excess excitation energy dissipates to the solvent with a 12 ps time-constant

24

O12 Prolonging lifetimes of metal-to-ligand charge transfer states

in iron-based photosensitizers

T. Harlang1, Y. Liu2, P. Persson3, V. Sundström1, K. Wärnmark2 et al. 1Lund University, Dep. Of Chemical Physics, 22100 Lund, Sweden

2Lund University, Centre for Analysis and Synthesis, Dep. Of Chemistry, 22100 Lund, Sweden 3 Lund University, Theoretical Chemistry Division, Dep. Of Chemistry, 22100 Lund, Sweden


Transition metal complexes play an important role in energy conversion applications [1], and as the demand for such systems rise, more sustainable alternatives to the prevalent Ru(II) photosensitizers are required. Due to high abundance and a similar electronic configuration, Fe(II) is an obvious candidate [2]. However, in common Fe(II) polypyridyl complexes, the metal-to-ligand charge transfer (MLCT) excited states, which play a key role in subsequent photochemical processes, are extremely short-lived (~100 fs) due to the low-lying deactivating high-spin (HS) 5T2 state [3]. To address this issue, the authors have been experimenting with metal-ligand interaction by incorporating strongly -donating N-heterocyclic carbene (NHC) ligands and have recently synthesized a series of new Fe(II) compounds [4], referred to as Fe(CAB).

To characterize and identify excited states of the Fe(CAB) compounds, femtosecond transient absorption spectroscopy was applied. The results were analyzed with a single value decomposition framework and compared to those of [Fe(II)(tpy)2]2+ (tpy= 2,2’:6’,2”-terpyridine), to identify (among other things) a 3MLCT state with a lifetime of 21ps, about two orders of magnitude longer than any equivalent state reported for other Fe(II) compounds.

REFERENCES [1] Hardin, B. E., Snaith, H. J. & McGehee, M. D. Nature Photonics 6, 162–169 (2012). [2] G. C. Vougioukalakisa, et al. Coord. Chem. Rev., 255, 2602-2621 (2011). [3] P. Gütlich, et al. Chem. Soc. Rev., 29, 419-427 (2000). [4] Liu, Yi, et al. Chem. Comm., 49, 6412 (2013).

Fig. 1 Excitation of the Fe(II) compounds, induces a metal-to-ligand charge transfer with

unprecedented lifetimes of up to 21ps.

hν

e-, τ=9ps

e-, τ<100fs

25

Fig. 1 Fragment ion transient for dithiane using 284nm pump and 400nm probe pulse. Fig. 2 Photolytic cleavage of dithiane (top) and DEDS (bottom). Fig. 3 Fragment ion transient for diethyl disulfide using 266nm pump and 400nm probe pulse.

O13 Photostability of disulfide bridges

M. A. B. Larsen1, A. B. Stephansen1, L. B. Klein1 and T. I. Sølling1

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


Proteins are highly dependent on their tertiary and quaternary structure for proper molecular function. The conformation and stability of proteins are often strongly influenced by disulfide bridges [1] which are known to cleave photolytically [2]. From an evolutionary perspective the photochemical stability of nature’s building blocks is of great importance and at a first glance disulfide bridges do not meet this requirement. Our femtosecond time resolved mass spectrometry experiments (TRMS) on dithiane (Fig. 1) showed a surprising intrinsic photochemical stability of the disulfide bond that is secured via the confinement of the cyclic structure. We showed that in spite of a repulsive excited state potential energy surface the molecule finds a safe return to the ground state through a conical intersection leading to the reformation of the disulfide bond [3]. These ultrafast dynamics are reflected in the oscillations observed in our TRMS experiments (Fig. 1).

We address whether the stability of dithiane is due to an intrinsic property of the S-S bond or arises from the carbon framework preventing the sulfur atoms from flying apart. Thus, we have investigated dithiane’s open-chain counterpart diethyl disulfide (DEDS) (Fig. 2). The TRMS experiment show the linear disulfide undergoes ultrafast S-S dissociation on a sub 50fs timescale without further ado (Fig. 3) [4]. Supported by the computed potential energy surfaces this shows that the photostability of dithiane must be ascribed to the cyclic structure exerting a restoring force that prevents the dissociation of the bond.

REFERENCES [1] T.E. Creighton; Bioessays 8 (1988) pp. 57-63. [2] W.E. Lyons; Nature 162 (1948) pp. 1004. [3] A.B. Stephansen, R.Y. Brogaard, T.S. Kuhlman, L.B. Klein, J.B. Christensen, and T.I. Sølling; J. Am. Chem. Soc. 134 (2012) pp. 20279-20281. [4] In press: A.B. Stephansen et al; Chem. Phys. (2014), http://dx.doi.org/10.1016/j.chemphys.2014.02.005

1. 2. 3.

26

I3 New data on photosynthetic light harvesting:

Is it slower than thought before?

Arvi Freiberg1,2

1Institute of Physics, University of Tartu, 142 Riia St., Tartu 51014, Estonia 2Institute of Molecular and Cell Biology, University of Tartu, 23 Riia St., Tartu 51010, Estonia


The studies of primary processes of photosynthesis are almost a century long, and it is widely considered that the most interesting questions in this regard have already been solved. Yet recent atomic force microscopy data on photosynthetic bacteria have shown significant variations of the assembly of their photosynthetic unit along with the environmental stress and growth conditions [1]. Motivated by this, we used the photosynthetic purple bacterium Rhodobacter sphaeroides to find out how the varying growth conditions influence the rates of energy migration towards the reaction center traps and the efficiency of charge separation at the reaction centers. To answer these questions we measured the spectral and picosecond kinetic fluorescence responses as a function of excitation intensity in the membranes prepared from the cells grown under different light environments. We conclude that [2]

In photosynthetic bacteria the rates of energy migration indeed depend on growth conditions.

Adaptation to low light slows down the migration rate but retains high energy trapping efficiency (>80%).

The efficiency decreases toward shorter excitation wavelengths within the lowest energy Qy absorption band of the antenna bacteriochlrophylls.

Neglecting losses due to the peripheral light harvesting complex 2, the exciton trapping time is about 61 ps irrespective the sample; by adding the peripheral antenna, the trapping time grows still longer.

The high light adapted samples contain a small population of disconnected peripheral antenna complexes.

REFERENCES [1] S. Scheuring and J.N. Sturgis, Chromatic Adaptation of Photosynthetic Membranes, Science, 309 (2005) pp. 484-487. [2] K. Timpmann, M. Chenchiliyan, E. Jalviste, J.A. Timney, C.N. Hunter, and A. Freiberg, Efficiency of Light Harvesting in a Photosynthetic Bacterium Adapted to Different Levels of Light, Biochem. Biophys. Acta (2014), submitted.

27

O14 Fluorescence lifetime of chlorophyll a reveals reversible

photo-protection mechanism in the green algae Tetraselmis under UV-stressed conditions

Arne Kristoffersen1, Svein Rune Erga2, Børge Hamre1 and Øyvind Frette1

1Department of physics and technology, University of Bergen 2Department of Biology, University of Bergen


The fluorescence lifetime is a very useful parameter in investigating biological materials on the molecular level, as it is independent of fluorophore concentration. The green algae Tetraselmis blooms in summer, and therefore its response to UV radiation is of particular interest. In vivo fluorescence lifetimes of chlorophyll a were measured under both normal and UV-stressed conditions of Tetraselmis. Fluorescence was induced by two-photon excitation using a femtosecond laser and a laser scanning microscope. The lifetimes were measured in the time-domain by time-correlated single-photon counting. Under normal conditions, the fluorescence lifetime was around 250 ps, while after exposure to UV-light the lifetime increased to around 400 ps, indicating increased non-photochemical quenching caused by shutting down the photosynthetic apparatus. The same sample was then dark-adapted overnight, resulting in a return of the lifetime to 250 ps, revealing that the photo-protective mechanism triggered by UV-light is reversible on a relatively short time scale.

Figure 1. Left: The laboratory showing the microscope and the presenting author. Right: Images of algae cells color-coded by fluorescence lifetime.

28

O15 Excited state interactions in simple amines:

Time-resolved gas phase studies.

Liv B. Klein1, James O. F. Thompson2, Theis I. Sølling1 and Dave Townsend2

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

2Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom.


A series of small, isomeric aliphatic C5H13N and alicyclic C5H11N amines has been investigated with time-resolved mass spectroscopy as well as time-resolved photoelectron spectroscopy using the velocity-map imaging (VMI) technique. The goal is to determine the effect of structural variations on the photophysics of amines following ultraviolet excitation.

Earlier studies have shown that for the tertiary amine N,N-dimethylisopropylamine (DMIPA), initial excitation to a 3p Rydberg state is followed by rapid internal conversion to the 3s state, which then decays with a longer time constant [1]. This is also seen in our data for both DMIPA and the unbranched N,N-dimethylpropylamine (DMPA). However, the degree of N-substitution seems to be of great importance, resulting in interesting differences in the the dynamics. One aspect of this is faster internal conversion for less substituted amines, an observation that contradicts standard density-of-state arguments. Deuteration at the nitrogen also leads to significantly increased decay times [2]. Both observations points towards a non-ergodic internal conversion process.

In addition, the photoelectron spectra for the secondary and primary amines show broad spectral features which strech across the high Rydberg binding energy region. This is ascribed to a strong coupling of the lowest 3s Rydberg state and a dissociative σ* state, as has been found for ammonia [3] and methylamine [4]. Our results shed new light on the interplay between amine photophysics and structure, in particular the effect of introducing one or more N-H bonds.

REFERENCES [1] J. L. Gosselin et al.; J. Phys. Chem. A 110 (2006) pp. 4251-4255. [2] L. B. Klein and T. I. Sølling; Chem. Phys. Accepted. [3] For instance: J. Biesner et al.; J. Chem. Phys. 91 (1989), pp. 2901-2911. [4] For instance: E. Kassab, J. T. Gleghorn, and E. M. Evleth; J. Am. Chem. Soc. 105 (1983), pp. 1746-1753.

Fig. 1 Abel inverted photoelectron VMI images for N,N-dimethylpropylamine

at selected pump-probe delay times Δt.

29

O16 Fluctuating antenna as an origin of multi-exponential

fluorescence kinetics in photosystem II

Jevgenij Chmeliov, Gediminas Trinkunas and Leonas Valkunas

Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio Ave. 9, Vilnius, Lithuania, and

Institute of Physics, Center for Physical Sciences and Technology, Gostauto 11, Vilnius, Lithuania Email: [email protected]

Photosystem II (PSII) is a huge pigment–protein supercomplex serving as a starting point for plant photosynthesis and ensuring both very efficient light harvesting and excitation energy transfer towards the reaction center (RC). Independently of sample preparation and the size of PSII antenna, time-resolved spectroscopic measurements usually reveal complex multi-exponential fluorescence decay kinetics [1] that for decades have been ascribed to reversible charge separation taking place in the RC. However, in this description the protein dynamics is not taken into consideration. Meanwhile, the intrinsic dynamic disorder of the light-harvesting proteins along with their fluctuating dislocations within the antenna [2] inevitably result in varying connectivity between pigment–protein complexes and therefore can also lead to non-exponential excitation decay kinetics. To account for this effect, we propose a simple conceptual model that describes excitation diffusion in a continuous medium of fractional dimensionality and deals with possible variations of the excitation transfer rates. Recently observed fluorescence kinetics of PSII of different sizes [1] are perfectly reproduced (Fig. 1) by using only two adjustable parameters instead of the many decay times and amplitudes required in standard analysis procedures; no charge recombination in the RC is required. The model is also able to provide valuable information about the structural and functional organization of the photosynthetic antenna and in a straightforward way solves various contradictions currently existing in the literature.

Fig. 1. (a) Schematic structures of variously sized PSII supercomplexes. (b) Experimental (symbols) and simulated

(lines) multi-exponential fluorescence decay kinetics in various PSII supercomplexes. For visual clarity, fluorescence kinetics in B8–BBY supercomplexes were multiplied by integer numbers 2–6, respectively.

REFERENCES [1] S. Caffarri, K. Broess, R. Croce, H. van Amerongen; Biophys. J. 100 (2011) pp. 2094–2103. [2] C. D. P. Duffy, L. Valkunas, A. V. Ruban; Phys. Chem. Chem. Phys. 15 (2013) pp. 18752–18770.

B7

C2 90% C S + 10% C2 2M

50% C 2SM+ 50% C S2 2 C S2 2M

C S2 2 2M

B8

B9 B10

B11

BBY

C S2 2 2M with 2 additional

LHCII trimers0 200 400 600 800 1000

0.01

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6

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ence

(a.u

.)

Time (ps)

BBYB11B10B9B8B7

(b)(a)

30

O17 Ultrafast dynamics in proteins explored using three-pulse

transient absorption spectroscopy.

Mikas Vengris1, Vladislava Voiciuk1, Donatas Zigmantas2 and Delmar S. Larsen3

1 Quantum Electronics Dept., Faculty of Physics, Vilnius University, Saulėtekio 10, LT1022 Vilnius, Lithuania

2 Dept. of Chemistry, University of California, Davis, One Shields Avenue Davis, CA 95616, USA 3 Chemical Physics Department, Lund University, Getingevägen 60, Lund S-22241, Sweden


Transient absorption spectroscopy has become a standard technique used for exploring ultrafast dynamics of molecular systems. However, the interpretation of transient absorption results is often problematic due to overlapping spectral bands containing contribution from different photoinduced pathways. In the past 10 years, multi-pulse transient absorption spectroscopy was developed and used to address complex issues regarding the ultrafast dynamics in pigment protein complexes [1,2]. Three applications are discussed in this contribution. Firstly, the technique is used to investigate the influence of mutations on the proton transfer in Green Fluorescent Protein (GFP). The results of pump-dump-probe experiments are compared between the wild-type GFP and its mutant H148D to draw conclusions about the influence of hydrogen bonds on the excited- and ground state proton transfer. A tentative model involving structural dynamics of the protein coupled to proton transfer pathway is proposed (Fig. 1). Second application is the investigation of excitation energy transfer dependence on the state of acceptor molecule (ground state versus excited state). As model systems, peridinin-chlorophyll-protein (PCP) and caroteno-zinc-phtalocyanine dyad are selected. Finally, the relationship between intramolecular charge transfer state and S1 state of peridinin in PCP and their energy transfer properties to chlorophyll are explored.

REFERENCES [1] M. Vengris, D.S. Larsen, E. Papagiannakis, J.T.M Kennis, and R. van Grondelle, In Analysis and Control of Ultrafast Photoinduced Reactions; Kühn, O., Wöste, L., Eds.; Springer-Verlag: Berlin Heidelberg, (2007) pp 750-774. [2] D.S. Larsen, I. H.M van Stokkum, M. Vengris, M.A. van der Horst, F.L. de Weerd, K.J. Hellingwerf, R. van Grondelle, Biophysical Journal 87 (2004) 1858-1872.

Fig. A tentative model proposed to interpred the dynamics observed in H148D mutant of GFP.

31

I4 Tracking energy flow through the intact photosynthetic

apparatus

Jakub Dostál1,2, Jakub Pšenčík2 and Donatas Zigmantas1

1Department of Chemical Physics, Lund University, P. O. Box 124, 221 00 Lund, Sweden. 2Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague, Czech

Republic. Email: [email protected].

Photosynthetic machinery in photosynthetic organisms consists of assemblies of different complexes, namely light-harvesting complexes and reaction centers. The energy transfer pathways and efficiency in isolated photosynthetic complexes depend on photophysical properties of pigments and their mutual arrangement. The energy harvesting and capture of the whole photosynthetic apparatus relies also on the spatial arrangement of photosynthetic complexes and coupling between them. Photosynthetic unit in green sulfur bacteria, responsible for primary light-absorption and charge-separation functions, comprise light-harvesting antenna chlorosome, Fenna-Matthews-Olson (FMO) complexes and type I reaction centers. Through the years energy transfer processes have been extensively studied in the isolated photosynthetic subunits. However, for understanding the entire picture of primary photosynthetic processes in green sulfur bacteria or in other photosynthetic organisms, it is essential to study intact photosynthetic units. Interestingly and contrary to the general believe, studies of the FMO complexes isolated together with reaction centers (without chlorosomes) indicated that energy transfer from FMO to reaction centers is rather inefficient.

We have used two-dimensional electronic spectroscopy (2DES) at 77 K to study excitation energy flow through the intact photosynthetic unit in cells of green sulfur bacteria Chlorobaculum tepidum. This method is especially well suited for investigating energy transfer and connectivity between the pigments with different transition energies. 2DES allowed us to monitor the excitation energy flow from chlorosome via FMO to the reaction centers, where the photochemistry occurs.

32

O18 Light-induced formation of the Pfr state of

bacteriophytochrome from Deinococcus radiodurans Heli Lehtivuori1, Heikki Takala1,2, Pasi Myllyperki ö3 Chukharev Vladimir4, Nikolai V.

Tkachenko4 and Janne A. Ihalainen1 1Nanoscience Center, Department of Biological and Environmental Sciences, University of Jyväskylä,

P. O. Box 35, 40014 Jyväskylä, Finland 2Department of Chemistry and Molecular Biology, University of Gothenburg, 40530 Gothenburg,

Sweden 3Nanoscience Center, Department of Chemistry, University of Jyväskylä, P. O. Box 35, 40014

Jyväskylä, Finland 4Department of Chemistry and Bioengineering, Tampere University of Technology, P. O. Box 541,

33101 Tampere, Finland Email: [email protected]

Bacterial phytochromes are optically sensitive proteins. The dynamic changes during the photoswitching between signalling and resting states take place in many different time scales, from femtoseconds to seconds. Detecting these changes in real time requires a combination of

several spectroscopic techniques, such as time-resolved absorption and fluorescence.

Here, the first aim is in understanding excited state dynamics of such molecules [1,2]. By using steady-state and time-resolved absorption and fluorescence techniques in the femto- to picosecond time scale we provide the composition of the excited state spectra of the bacterial phytochrome compartments. Secondly, we describe our flash-photolysis studies revealing time-resolved UV-Vis spectra during the chromoprotein photoconversion for full-length DrBphP and phytochrome fragments DrCBD, DrCBD-PHY. These spectral changes stand for the response of the chromophore to the structural changes of the protein environment during the photoconversion process, and reveals important information about interactions between chromophore and protein [3]. In the flash-photolysis data the first observable event is the

decay of Lumi-R state species with time constant of around 50 μs, after which the formation of the Pfr state via Meta-states takes place. Thus, our studies reveal comprehensive kinetics, from femtoseconds to milliseconds, of the light-induced formation of the Pfr state of Deinococcus radiodurans phytochrome proteins.

REFERENCES [1] H. Lehtivuori, I. Rissanen, H. Takala, J. Bamford, N. V. Tkachenko, J. A. Ihalainen (2013) J. Phys. Chem. B., 117, 11049–11057. [2] K. C. Toh, E. A. Stojković, I. H. M. van Stokkum, K. Moffat, J. T. M. Kennis (2011) Phys. Chem. Chem. Phys., 13, 11985–11997. [3] H. Takala, A. Björling, O. Berntsson, H. Lehtivuori, S. Niebling, M. Hoernke, I. Kosheleva, R. Henning, A. Menzel, J. A. Ihalainen, S. Westenhoff, (2014) Nature, accepted.

Fig. 1 Region surrounding the biliverdin chromophore. Biliverdin is colored orange. Some important amino acids, pyrrole water and two other waters are indicated. Structure Figure was generated using Pymol (Delano Scientifi

33

O19 Energy transfer pathways in Fucoxanthin-Chlorophyll Protein complex revealed by two dimensional optical spectroscopy

Andrius Gelžinis1,2, Vytautas Butkus1,2, Egidijus Songaila2, Ramūnas Augulis2, Andrew Gall3, Claudia Buchel4, Bruno Robert3, Donatas Zigmantas5, Darius Abramavicius1,

and Leonas Valkunas1,2

1Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio 9-III, 10222 Vilnius, Lithuania

2Center for Physical Sciences and Technology, Gostauto 9, 01108 Vilnius, Lithuania 3Institut de Biologie et Technologies de Saclay, Bât 532, Commissariat à l'Energie Atomique Saclay,

91191 Gif sur Yvette, France 4Institut für Molekulare Biowissenschaften, Universität Frankfurt, Max-von-Laue-Straße 9, Frankfurt,

Germany 5Department of Chemical Physics, Lund University, P.O. Box 124, 22100 Lund, Sweden


Diatoms are one of the most important group of eukaryotic phytoplankton, that accounts for nearly a quarter of the global primary production [1]. In diatoms the light-harvesting function is performed by its light-harvesting complex, termed the fucoxanthin-chlorophyll protein (FCP). In addition to chlorophylls a and c, it contains carotenoid fucoxanthin, which absorbs strongly in the blue-green regions, helping diatoms to capture light underwater.

To analyze excitation energy transfer in FCP, we have performed two color two dimensional optical spectroscopy measurements, exciting the S2 state of fucoxanthins. Example spectra are shown in Fig. 1. For further analysis we have constructed 2D decay associated spectra [2], which allowed us to identify the dominant kinetic processes in the complex. Our results show that there are at least two species of fucoxanthin in FCP. We also find that the “red” (with lower S2-S0 transition energy) fucoxanthins must be positioned closer to chlorophyll a molecules.

REFERENCES [1] A. Falciatore and C. Bowler, Annu. Rev. Plant Biol. 53,109 (2002). [2] J. A. Myers et al, J. Phys. Chem. Lett. 1, 2774 (2010).

Fig. 1 Two color two dimensional optical spectral of

FCP complex at different waiting times.

34

O20 Population- and Coherent- Dynamics in the Fenna-

Matthews-Olson Complex Characterized by 2D Electronic Spectroscopy.

Erling Thyrhaug,1 Karel Zidek,1 Jakub Dostal,1 and Donatas Zigmantas*1

1Department of Chemical Physics, Lund University, Getingevägen 60, 22241 Lund, Sweden Email: [email protected]

Since the determination of its crystal structure, the Fenna-Matthew-Olson (FMO) complex[1] – a homo-trimer situated between the light-harvesting chlorosomes and the photosynthetic reaction center of green sulphur bacteria - has become the favored model system for energy transfer in photosynthetic systems. Beyond the knowledge of absolute positions of the 7(8) Bacteriochlorophyll a chromophores in each monomer of the homo-trimer, the complex is favored because of its relative spectral simplicity. The weak interunit chromophore coupling results in a spectrum showing transitions to only 7 unique states, which initially fostered optimism that the complex could work as a ”Rosetta stone” for excitonic energy transfer. The intense experimental scrutiny[2,3,4] the complex has been subjected to and the vast literature of sometimes significantly disagreeing theoretical treatments[5,6,7] is clear evidence of a situation far more complicated than was initially assumed. Both experimental and theoretical investigations only intensified when long-lived oscillations – interpreted as electronic coherences with picosecond lifetimes - were observed in the two-dimensional electronic spectra of FMO in the mid 2000’s[8]. We here investigate energy transfer dynamics and oscillatory signals in FMO by two-dimensional electronic spectroscopy, exploiting significant improvements in time- and spectral- resolution of our instrument relative to earlier measurements to provide accurate transfer kinetics. The oscillatory signals are monitored and separated into distinct contributions by exploitation of different polarization schemes.

REFERENCES [1] R.E. Fenna, B. W. Matthews; Nature 258 (1975) pp. 573-577. [2] M. Wendling, et.al; Photosynthesis Research 71 (2002) pp. 99-123. [3] S. Savikhin, D. R. Buck, W. S. Struve; Journal of Physical Chemistry B 102 (1998) pp. 5556-5565 [4] T. Brixner, et.al; Nature 434 (2005) pp. 625-628 [5] J. Adolphs, T. Renger; Biophysical Journal 91 (2006) pp. 2778-2797 [6] R. M. Pearlstein; Photosynthesis Research 31 (1992) pp. 213-226 [7] D. Abramavicius, S. Mukamel; Journal of Chemical Physics 134 (2011) 174504 [8] G.S. Engel, et.al; Nature 446 (2007) 782-786

Fig. 1: Low-temperature two-dimensional spectra of FMO in 1:3 water:glycerol at

increasing pump-probe delays.

35

O21 2D electronic spectra of Marcus electron transfer.

Thorsten Hansen1 1Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK 2100 Copenhagen Ø, Denmark.

Email: [email protected] .

Coherent multi-dimensional spectroscopy enables direct measurement of the coherences associated with dynamic processes in photochemical systems. Most experiments have reported on energy migration, often in photosynthetic antenna systems. A few recent papers discuss electron transfer.

Based on a Keldysh contour formulation of four-wave mixing spectrosopy [1], recently extended to include molecular vibrations, we discuss theoretically the coherent features of the prototypical electron transfer – Marcus electron transfer.

REFERENCES [1] T. Hansen, and T.Pullerits; J.Phys.B:At.Mol.Opt. 45 (2012) 154014.

36

I5 Studies of ultrafast proton/hydrogen transfer processes

Jacek Waluk

Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44, 01-224 Warsaw, Poland Email: [email protected].

Proton or hydrogen transfer processes are ubiquitous in nature. Due to the quantum character of the proton, proper description of these reactions is difficult and requires multidimensional potential energy surfaces, i.e., taking into account different vibrational modes which may contribute to the reaction path. Tunneling also may play an important role.

I will review results of our investigations of different classes of organic molecules which exhibit ground and excited state tautomerization involving one or two hydrogen atoms [1-5]. All these systems have a common feature: they form intra- or intermolecular hydrogen bonds. The strength and topology of these bonds are crucial for the kinetics of tautomerization. For instance, varying the dimensions of the inner cavity of porphycene (Figure 1) leads to changes in tautomerization rates exceeding three orders of magnitude [2]. In bifunctional hydrogen bond donor-acceptor molecules, able to form complexes with water or alcohols (Figure 2), photophysical properties are strongly dependent on the stoichiometry and structure of such solvates [5].

Examples will also be presented of photoinduced proton transfer accompanied, or competing with large amplitude motions, such as twisting [3].

REFERENCES [1] J. Waluk, in CRC Handbook of Organic Photochemistry and Photobiology, ed. M. Oelgemoeller, Griesbeck. A.

Ghetti, F., CRC Press, 2012, pp. 809-829. [2] P. Fita, N. Urbańska, C. Radzewicz, and J. Waluk, Chem.- Eur. J.15 (2009) pp. 4851-4856. [3] E. Nosenko, G. Wiosna-Sałyga, M. Kunitski, I. Petkova, A. Singh, W. J. Buma, R. P. Thummel, and J. Waluk,

Angew. Chem., Int. Ed. Engl. 47 (2008) pp. 6037-6040. [4] J. Waluk, Acc. Chem. Res. 39 (2006) pp. 945-952. [5] J. Waluk, Acc. Chem. Res. 36 (2003) pp. 832-838.

N NH

OHH

N NH

OH

HOH

H

... ...

...

... ...

Fig. 2. Two different stoichiometries of complexes of 1H-pyrrolo[3,2-h]quinoline with water.

HN

NNH

N

...

...

Fig. 1. Porphycene; intramolecular hydrogen bonds indicated by dots.

37

O22 Directed Energy Transfer in Films of CdSe Quantum Dots

Kaibo Zheng1, Karel Žídek1, Mohamed Abdellah1,3, Nan Zhu2, Pavel Chábera1, Nils Lenngren1, Qijin Chi2, Tõnu Pullerits1

1 Department of Chemical Physics, Lund University, Box 124, 22100, Lund, Sweden 2 Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark

3 Department of Chemistry, Faculty of Science, South Valley University, Qena 83523, Egypt Email: [email protected]

Semiconductor quantum dots (QDs) hold promises for a broad spectrum of applications. In the development of devices, QDs are often densely packed to form a thin film with strong absorption or emission. Förster resonant energy transfer (FRET) induced by electronic coupling between QDs is an essential process for function of such devices.1

It is generally accepted that the usual point dipole approximation in FRET is valid if the excitation donor and acceptor separation is significantly larger than the size of them. The separation between QDs in the densely packed films is usually smaller than the size of QDs, so that the simple point-dipole approximation, widely used in the conventional approach, can no longer offer quantitative description of the FRET dynamics in such systems.2

Here, we report the investigations of the FRET dynamics in densely packed films composed of multi-sized CdSe QDs using ultrafast transient absorption spectroscopy and theoretical modeling. Pairwise inter-dot transfer time was determined in the range of 1.5 to 2 ns by spectral analyses which enable to separate the FRET contribution from intrinsic exciton decay. A rational model is suggested by taking into account the distribution of the electronic transition densities in the dots and using the film morphology revealed by AFM images. The FRET dynamics predicted by the model are in good quantitative agreement with experimental observations without adjustable parameters. Finally, we employed the experiment and theory to determine energy funneling in ordered QD layers, which reveal that three well controlled QD layers can provide exciton funneling efficiency above 80% from the most distant layer (see Fig. 1 for an example of theoretical stimulation). Thereby, utilization of directed energy transfer can significantly improve light harvesting efficiency of QD devices.

REFERENCES (1) K. B. Zheng, K. Žídek, M. Abdellah, M. Torbjörnsson, P. Chábera, S. Shao, F. Zhang, T. Pullerits, J. Phys. Chem.

A 117 (2012) pp. 5919–5925.

(2) W. J. D. Beenken, T. Pullerits, J. Chem. Phys.120 (2004) pp. 2490–2495.

Fig. 1 Theoretical stimulation of FRET in ordered QD films after a random A-type QD (blue) is excited. Upper panel: Example of a QD film consisting of three subsequently deposited monolayers of A (blue), B (green), and C (red) QDs. Lower panel: Analogous film of QDs with a double layer of B-type QDs.

38

O23 Ultrafast electronic relaxation and vibrational

cooling dynamics of Au144(SC2H4Ph)60 nanocluster probed by transient mid-IR spectroscopy

Satu Mustalahti1, Pasi Myllyperkiö1, Tanja Lahtinen1, Kirsi Salorinne1,

Sami Malola2, Jaakko Koivisto1, Hannu Häkkinen1,2 and Mika Pettersson1 Nanoscience Center, Departments of Chemistry1 and Physics2, P.O. Box 35, FI-40014

University of Jyväskylä, Finland Email: [email protected]

Thiol protected gold nanoclusters show molecule-like behavior when their diameter is below 3 nm, while larger particles show metallic behavior. Au144(SC2H4Ph)60 cluster can be considered to represent the borderline between molecular and metallic clusters.[1] Although the structure of this cluster has not been experimentally resolved, careful analysis has been performed to confirm its exact atomic composition, and synthesis and purification methods have been developed to produce monodisperse samples.[2,3] This cluster has been shown to have a broad absorption range with electronic absorptions of gold core and the ligands in UV/Vis/NIR/mid-IR region and vibrational absorptions of IR chromophores of the ligands in mid-IR region.[4]

In this work, femtosecond transient mid-IR spectroscopy was used to probe the electronic relaxation and vibrational cooling dynamics of Au144(SC2H4Ph)60 cluster. The experiment was designed to simultaneously probe electronic and vibrational dynamics by exciting the sample with 652 nm visible laser pulse to prepare an electronic state localized in the gold core and by probing transient absorption of a stretching vibration localized on benzene ring of the ligands. Based on these experiments the electronic relaxation process of gold core proceeds with a time constant of 1.5 ps simultaneously heating the phonon bath of the cluster and finally the heat is dissipated to solvent with a time constant of 29 ps.

These results establish a correlation between exact composition and energy relaxation and dissipation dynamics of a small nanocluster which can be utilized to compare structure-function relationships when more data becomes available. In studied clusters the metal-ligand interface modes are strongly anharmonically coupled to probed mode which also provides a connection between the cluster core temperature and the vibrational shift of ligand molecules. This information is relevant for applications in which small gold nanoclusters are used for targeted heating of small biomolecular structures.

REFERENCES [1] O. Lopez-Acevedo, J. Akola, R. L. Whetten, H. Grönbeck, and H. Häkkinen; J. Phys. Chem. C 113 (2009) pp. 5035-5038. [2] H. Qian and R. Jin; Chem. Mater. 23 (2011) pp. 2209-2217. [3] K. Salorinne, T. Lahtinen, J. Koivisto, E. Kalenius, M. Nissinen, M. Pettersson, and H. Häkkinen; Anal. Chem. 85 (2013) pp. 3489-3492. [4] J. Koivisto, S. Malola, C. Kumara, A. Dass, H. Häkkinen, and M. Pettersson; J. Phys. Chem. Lett. 3 (2012) pp. 3076-3080.

39

O24 Charge carrier recombination in S-doped InP nanowires


Department of Chemical Physics, Lund University, Box 124, 221 00 Lund, Sweden Email: [email protected]

We have investigated the dynamics of charge carriers in a series of as grown InP nanowires (NW) with different sulfur doping levels. Time resolved photoinduced luminescence (TRPL) and transient absorption (TA) measurements have been employed to investigate radiative and nonradiative charge recombination processes. From TRPL measurement, we find that PL decay slows down and then levels off with increasing excitation power in the NW with low S concentration. This effect can be explained by PL decay due to charge trapping combined with saturation of traps at high excitation. We have confirmed the trap saturation by PL pump-probe experiment (Fig. 1). Less trap filling was observed at higher S-doping level due to (much) higher number of traps in those NWs. From TA measurement, we find that only a small part of the photo-generated charges decay radiatively whereas most of charges are trapped at NW surface and decay non-radiatively. We conclude that S doping introduces additional traps to InP NW and reduce the overall PL intensity. We also observe that PL decay is sensitive to the environment and irradiation suggesting that these NWs can be used as gas sensors.

0 20 40 60

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Fig.1 Schematic of the PL pump-probe experiment and the influence of the strong Pump on the probe-induced PL decay. The PL lifetime increase with Pump ON is due to the trap filling by the

pump pulse

40

O25 On the role of J-aggregation in stabilization of triplet states in

nickel phtalocyanine derivative

1David Rais, 1Miroslav Menšík, 1Jiří Pfleger, 1Petr Toman and 2Jiří Černý 1Institute of Macromolecular Chemistry, Academy of Sceinces of the Czech Republic, Heyrovský Sq.

2, 162 06 Prague 6, Czech Republic 2 Centre for Organic Chemistry Ltd., Rybitví 296, 533 54 Rybitví, Czech Republic


Nickel phthalocyanine complexes are photostable dyes, known to show rapid non-radiative deactivation of the photo-excited state through internal conversion which could allow some practical applications, including photoprotection and oxygen-free photodynamic therapy. The butoxy substitution of NiPc plays an important role for drug delivery, but also greatly influences its photophysics. We have prepared novel peripherally substituted Ni(II) 2,3,9,10,16,17,23,24-octabutoxyphthalocyanine and characterized the deactivation pathway of the population of its photoexcited state S1(π,π*) in solution by ultrafast transient absorption spectroscopy and quantum chemical calculations. We present experimental and theoretical evidence for a kinetic model in which the photoexcited S1 state undergoes ultrafast intersystem crossing to a triplet state with 1.60 ps lifetime, which subsequently decays to a ground state through a pathway of lower-lying intermediate triplet states, with ground-state recovery lifetime of 814 ps. Additionally, the photoexcitation created a triplet state with relatively long lifetime, (> 20 ns), with quantum yield of about 4 %. Connection of this long-lived state with J-aggregation is discussed. Namely, we built-up a scheme for an intramolecular energy transfer process following the photoexcitation that consists of two independently evolving branches (one for long-lived triplet state and the other for fast decaying states) described by population concentrations 푐 (푡). The measured differential transient absorption spectrum is factorized as ∆퐴(푡, 휆) = ∑ 푐 (푡)휀 (휆) and fitted values are shown in Fig. 1. The long-lived component contains a signature of J-aggregation formation at 770 nm. Moreover, long-lived state was also confirmed by spectrometric measurement of the quantum yield of singlet oxygen photoproduction. This is important finding for the application areas, which rely on fast non-radiative deactivation of the excited state.

Acknowledgement: This work was supported by the grants No. COST LD 14011 and KONTAKT LH 121 86 of MEYS of the Czech Republic.

500 600 700 800

-0,03

-0,02

-0,01

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0 1 2 10 100 10000

1

SADS and its lifetime, i (ps)

1 (1.6) 2 (9.4) 3 (813)

1b (>2.104)

i()(S

ADS)

Wavelength, (nm)

Species Associated Differential Spectra (SADS)and fitted excited state populations Ci(t)

monomer

J-aggr.

Rel

. con

cent

ratio

n, c

i

Time, t (ps)

Fig. 1 Fitted decomposition of transient absorption spectrum ∆퐴(휆, 푡)for the manifold of excited state in

studied compound. Life-time of a long-lived triplet state associated with J-aggregation is longer than 20 ns.

41

O26 Dissociation of electron-hole pairs in planar heterojunction

organic solar cells – electroabsorption study.

A. Devižis1,2, J. De Jonghe2, S. Jenatsch3, R. Hany3, F. Nüesch3, V. Gulbinas1 and J.-E. Moser2

1Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania. 2Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne Station

6, CH-1015 Lausanne, Switzerland. 3Swiss Federal Laboratories for Materials Testing and Research, Überlandstr. 129, CH-8600

Dübendorf, Switzerland Email: [email protected].

Planar heterojunction (PH) structure serves as an ideal model system for the investigation of the electrical charge separation phenomenon in organic solar cells because geometrical parameters of the system are precisely known and separation of charges takes place in a well-defined geometrical plane. Photogenerated charge carriers change the electric field in the device and these changes can be monitored employing electric-field sensitive optical probe [1].

We investigated free charge generation and extraction in small molecule Cy3P/fullerene planar heterojunction devices [2] by means of time-resolved electroabsorption (Stark effect) and complementary measurements of photocurrent, transient absorption and time-resolved fluorescence.

Dynamics of the photogenerated charge extraction was reconstructed from the perturbation of the electric field caused by the drift of charge carriers. Free electrons are extracted from the C60 layer within a few ps at an applied electric field of 1 MV/cm corresponding to the mobility of the order of 1 cm2/(V∙s). The excitons in the Cy3P layer are quenched approximately on the same time scale, within a few or several ps. However, generation of free carriers by dissociation of electron-hole pairs at the C60/Cy3P interface is much slower and depends on the strength of the applied electric field. Presumably, the dissociating charge transfer state at the Cy3P/C60 interface is vibrationally relaxed and the process is thermally driven. We suggest that a slow dissociation of electron-hole pairs at the donor/acceptor interface is typical for organic semiconductors.

REFERENCES [1] Gélinas, S., Rao, A., Kumar, A., Smith, S. L., Chin, A. W., Clark, J., ... & Friend, R. H. (2014) Science, 343(6170), 512-516 [2] Fan, B., de Castro, F. A., Heier, J., Hany, R., & Nüesch, F. (2010). Organic Electronics, 11(4), 583-588.

Fig. 1 Charge formation in C60/Cy3P PH solar cell and the

resulting redistribution of the electric field - 1) diffusion of the

exciton ; 2) formation and splitting of the electron-hole pair; 3) drift of

free charge carriers.

42

O27 Exciton-exciton annihilation in metallo-supramolecular

polymers with Zn(II) ion-couplers studied by pump-probe transient absorption spectroscopy

David Rais1, Pavla Bláhová2, Miroslav Menšík1, Jan Svoboda2, Jiří Vohlídal2 and Jiří Pfleger1

1Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Heyrovského nám. 2, 162 06, Prague 6, Czech Republic.

2Charles University in Prague, Faculty of Science, Department of Physical and Macromolecular Chemistry, Hlavova 2030, 128 40 Prague 2, Czech Republic.


Large effort in the research of conjugated polymers is dedicated to the synthesis of soluble materials, which allow solution-casting of thin films by wet device manufacturing processes. Instead of the usually adopted method of achieving a desired solubility by an attachment of solubilizing side groups to the semiconducting polymer backbone, self-assembly metallo-polymer approach follows this aim by introducing two non-covalent, chelating groups into the structure of soluble oligomer precursor. The groups then allow polymer chain formation by chelating two oligomer units to the same metal ion. In this report, we present photophysical investigation of series of

structurally-related materials based on bis-terpyridine-oligothiophene polymers (Fig. 1). As opposed to the solutions, in thin films of self-assembled metallo-polymers we observed signs of mutual exciton interactions, resulting in their annihilation. In the present work, we extended the kinetic model used in previous works [1,2] by incorporation of intersystem crossing phenomenon. From the analysis of the decay of the exciton population (Fig. 2), we deduced the predominant microscopic mechanism of the energy transfer that facilitates the interactions (Förster or Dexter model). The results are important for the future development of the materials, towards their intended application in optoelectronic devices.

REFERENCES [1] W. Staroske, M. Pfeiffer, K. Leo, M. Hoffmann; Phys. Rev. Lett. 98 (2007) p. 197402. [2] H. Marciniak, X.-Q. Li, F. Würthner, S. Lochbrunner; J. Phys. Chem. A 115 (2011) pp. 648–654.

Fig. 2 Pump energy Ipump dependent

excited state density evolutions derived by spectral integration and scaling of transient

absorption signal recorded in spectral region of ground-state bleaching. In the case of the highest pump energy, the evolutions of singlet and triplet exciton densities are plotted also separately.

Fig. 1 Representative chemical structure of

studied metallo-supramolecular polymers.

43

O28 Charge carrier generation and transport in different

stoichiometry APFO3:PC61BM solar cells.

Vytenis Pranculis1, Yingyot Infahsaeing2, Zheng Tang3, Andrius Devižis1, Dimali Vithanage2, Carlito Ponseca Jr.2, Olle Inganäs3, Arkady Yartsev2, Vidmantas Gulbinas1

and Villy Sundström2

1Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania. 2Chemical Physics, Lund University Box 124, 221 00 Lund, Sweden.

3Biomolecular and Organic Electronics, Department of Physics (IFM), Linkopings University, SE-58183 Linkoping, Sweden


The bulk heterojunction (BHJ) is currently a leading architecture of organic solar cells, with efficiencies reaching 10%1. The ability of holes to rapidly move through conjugated polymer chains was believed to be one of the major advantages of conjugated polymers over small molecules for their use in BHJ solar cells. However, efficiencies of solar cells based on various polymers and on small molecules are surprisingly similar, suggesting that polymer conjugation may not be that crucial for good solar cell performance. On the other hand, attempts to substitute fullerene derivatives with other electron accepting molecules have been less successful. Moreover, high efficiency solar cells need a high fullerene content of 50% or more, significantly exceeding percolation threshold for the electron motion.

We studied carrier drift dynamics in APFO3:PC61BM solar cells of varied stoichiometry (2:1, 1:1 and 1:4 APFO3:PC61BM) over a wide time range, from sub-ps to µs with a combination of ultrafast optical electric field probing and convention-al transient integrated photocurrent techniques. Carrier drift and extraction dynamics are strongly stoichiometry-dependent: the speed of electron or hole drift increases with higher concentration of PC61BM or polymer, respectively. The electron extraction from a sample with 80% PC61BM takes place during hundreds of picoseconds, but slows down to sub-microseconds in a sample with 33% PC61BM. The hole extraction is less stoichiometry dependent – it varies form sub-nanoseconds to tens of nanoseconds when the PC61BM concentration changes from 33% to 80%. The electron extraction rate correlates with the conversion efficiency of solar cells, leading to the conclusion that fast electron motion is essential for efficient charge carrier separation preventing their geminate recombination.

REFERENCES [1] Green, M. A.; Emery, K.; Hishikawa, Y.; Warta, W.; Dunlop, E. D. Prog. Photovoltaics Res. Appl. 1 (2013), 21.

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fiel

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op

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Time (ns)

Fig. 1 Normalized electric field kinetics of different blending ratio APFO3:PC61BM cells and of the neat APFO3 film. The cells were reverse biased at 4 V. The inset shows the initial part of the kinetics, revealing the exciton contribution in neat polymer film.

44

O29 Nanostructure of Organic Photovoltaic Devices

Revealed by Ultrafast Spectroscopy

Almis Serbenta, Paul H. M. van Loosdrecht, and Maxim S. Pshenichnikov

Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747 AG, Netherlands.


Plastic solar cells are promising candidates for sustainable energy production. One of the key ingredients deter-mining the efficiency of these solar cells is the nano-scale texture (i.e. morphology) of the used donor-acceptor blend [1]. Morphology is a challenging property not only to control but even to characterize as this generally requires chemical selectivity combined with nanometer spatial resolution. Standard methods for studying nanostructures (i. e. AFM, TEM, SAXS, etc.) either lack spatial resolution and/or require special sample preparation [1]. Here we show how ultrafast pump-probe spectroscopy can be used to obtain information on morphology by utilization of fullerene excitons [2]. The main advantage of the proposed method lies in its capability to elucidate average diameter of nm-sized PC71BM clusters non-invasively.

In the proposed technique, a pump pulse photon selectively creates an exciton in a PC71BM domain which after diffusion to the interface dissociates into a hole on the polymer and an electron on the fullerene. The presence of the hole induces absorption of the polymer in the infrared region which is probed by a delayed probe pulse [3]. From the efficiency of exciton-to-hole generation at different times (fig.1b symbols), a characteristic size of the PC71BM domains is deduced using a simple surface-to-volume argument, i.e. using the ratio of short-time interfacial (<1 ps) and long-time diffusion-mediated (>10 ps) contributions. To verify the validity of this simple approach, extensive Monte Carlo simulations were performed of excitons diffusing in a randomly modulated energy landscape. The results of the simulations reproduced excellently the experimental data (fig.1b, solid curve line) validating the use of to the simple approach.

REFERENCES [1] W. Chen et. al., Energy Environ. Sci. 5 (2012) pp. 8045-8074. [2] A. A. Bakulin et. al., Adv. Func. Mat. 20 (2010) pp. 1653-1660. [3] A. A. Bakulin et. al., Science 335 (2012) pp. 1340-1344.

Fig.1. (a) Concept of the technique. Lightning bolt: PC71BM optical excitation, green arrow: exciton diffusion inside a PC71BM domain, yellow arrow: exciton dissociation via hole transfer to the polymer. (b) Representative transient of

the hole concentration. The orange shaded area – interfacial hole transfer (<1 ps), the green shaded area – bulk exciton diffusion (>10 ps).

45

Poster presentations

46

47

P1 Photo-Physical Properties of Highly Ordered

Pseudoisocyanine Films and Heterostructures with [6,6]-Phenyl‑C61-butyric Acid Methyl Ester

Oleksandr Boiko1,2, Marius Franckevičius1, Vytenis Pranculis 1, Vassili Nazarenko2 and Vidmantas Gulbinas1

1 Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania 2 Institute of Physics, National Academy of Science of Ukraine, prospect Nauky 46, Kiev-39, 03039,

Ukraine Email: [email protected]

We present results of study of absorption and fluorescence properties of highly ordered pseudoisocyanine chloride (PIC) films and bilayer heterostructures with [6,6]-phenyl‑C61-butyric acid methyl ester (PCBM). The PIC films were prepared by vertical spin-coating method and consisted of molecular J-aggregates, with in-plane orientation. The orientational order with dense packing was preserved when the aggregates were deposited from the liquid-crystalline solutions into thin films by directed coating and drying. The photo-physical properties have been investigated by means of steady-state and time-resolved absorption and fluorescence spectroscopy. The films showed a large anisotropy, which reveals high degree of order parameter of obtained PIC films. The difference between J-band absorption and fluorescence spectra of PIC/PCBM heterostructures in comparison with pristine PIC film are discussed. Changes of PIC fluorescence in heterostructures suggest formation of collective states with intermolecular charge transfer at PIC/PCBM interface.

48

P2 Excitation dynamics in single-walled carbon nanotubes

wrapped with PFO-BPy.

Angela Eckstein1, Domantas Peckus1,2, Vidmantas Gulbinias1, Tomas Tamulevičius2, Imge Namal2 and Tobias Hertel2

1Center for Physical Sciences and Technology, A.Gostauto 11,LT-01108 Vilnius. 2 Institute of Materials Science of Kaunas University of Technology, Savanorių Ave. 271, Kaunas LT-

50131, Lithuania, 2University of Würzburg, Physical Chemistry Department, Am Hubland 97074 Würzburg.


Single-walled carbon nanotubes (SWNTs) are potential materials for future electronic devices because of their unique electronic properties. The fast carrier relaxation times make them a key component in ultrafast photonic devices. There were also attempts to use them in solar cells. Wraping the tubes with polymers helps to separate some particular SWCN type and to prevent of making boundles. However, polymers used for wraping also change electronic properties of nanotubes.

We address excited state dynamics in SWNTs that are wrapped with poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6-{2,2-bipyridine})] (PFO-BPy) in order to select tubes with the (6,5)-chirality [1]. Because of narrower energy gap of the SWNTs the energy levels form a so-called type-I heterojunction where energy transfer is possible, however not necessarily fast and efficient.

Flourescence decay measurements show significant quenching of the polymer fluorescence due to the SWNTs and lead to the conclusion of efficient energy transfer. The quenching is very fast in solid films, much faster than the time resolution of about 3 ps of our measurements. Whereas fluorescence quenching in solutions is less efficient, polymer fluorescence has slow decay component, which should be attributed to polymer chains or their fractions less tightly wrapped around SWNTs.

In conclusion the energy transfer is very fast despite very weak overlap of absorption and fluorescence spectra. Therefore the transfer mechanism still remains not clear.

REFERENCES [1] Ozawa, H., Ide, N., Fujigaya, T., Niidome, Y. & Nakashima, N. One-pot Separation of Highly Enriched (6,5)-Single-walled Carbon Nanotubes Using a Fluorene-based Copolymer. Chemistry Letters 40, 239–241 (2011).

Fig. 1 Flourescence decay of PFO-

BPy

49

P3 Time-resolved x-ray diffraction study of the phonon

dispersion in InSb nanowires.

A. Jurgilaitis1,2, H. Enquist2, B. P. Andreasson1, A. I. H. Persson1, B.M. Borg5, P. Caroff3, K.A. Dick1,4, M. Harb1,2, H. Linke1, R. Nüske1, L. E. Wernersson5 and

J. Larsson1 1Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden.

2MAX IV laboratory, Lund University, P.O. Box 118, Lund, Sweden. 3Department of Electronic Materials Engineering, Research School of Physics and

Engineering, The Australian National University, Canberra, ACT 0200, Australia. 4Division of Polymer and Materials Chemistry, Department of Chemistry, Lund University,

P.O. Box 124, SE-221 00 Lund, Sweden. 5Department of Electrical and Information Technology, Lund University, P.O. Box 118, SE-

221 00 Lund, Sweden. Email: [email protected]

We present a recent experiment at the current time resolved X-ray diffraction (TXRD) beamline, D611 at MAX-lab. Here we show a nondestructive way of measuring the phonon dispersion relation in nanowires using TXRD. By measuring phonon dispersion relation one can extract sound velocity in the material. We find that speed of sound InSb nanowires is lower than in the bulk InSb material, and conclude that the major origin of the reduced sound speed is due to changes in elastic constants compared to the bulk material [1].

REFERNCES [1] A. Jurgilaitis, H. Enquist, B. P. Andreasson, A. I. H. Persson, B. M. Borg, P. Caroff, K. A. Dick, M. Harb, H. Linke, R. Nüske, L.-E. Wernersson, and J. Larsson. Nano Lett., 14 (2), (2014), 541–546.

Fig. 1 Simulated dispersion relation for (a) bulk InSb. The slope of the dispersion curve is 3880 m/s, which is the bulk speed, (b) nanowires with elastic constants giving the best fit to the experimental sound speed 2880 m/s.

50

P4 Fluorescence properties of rhodamine 6G in mesoscopic

micelle-silica matrices

A. Kazakevičius1, V. Gulbinas1 and G.M. Telbiz2 1Center for Physical Sciences and Technology, Goštauto 11, Vilnius

2L. V. Pisarzhevsky Institute of Physical Chemistry, NASU, pr. Nauki 31, Kyiv, Ukraine Email: [email protected]

Mesoscopic silica films doped with dye molecules have some unique properties and potentially can be used in gas sensors, waveguides or in all-optical ultrafast switching devices. Dye-dye and dye-matrix interactions strongly influence optical properties of such films leading fluorescence quenching, which may be undesirable in some applications. When producing thin films, dye molecules tend to aggregate when high concentration is reached. This process greatly affects absorption and particularly fluorescence properties of the films. It hinders formation of films with high absorption coeffcient and good fluorescence properties. It was demonstrated, that dye incorporation in mesoscopic structures allows to achieve higher non agregated dye concentrations than in pure films or in polymer matrixes [1]. However, at very high dye concentrations aggregation still occurs in mesoscopic matrices.

In this experiment rhodamine 6G (R6G) molecules were incorporated in pluronic P123 micelles and subsequently mixed with SiO2. The obtained solution was used to form hundreds of nanometers thick films. The micelles of P123 were used to reduce dye – silica interaction. A range of R6G concentrations from 3.6 × 10-3 g/ml to 7.6 × 10-2 g/ml was selected to investigate concentration dependent optical properties and to study aggregation of dye molecules. Stationary and time resolved fluorescence measurements as well as femtosecond transient absorption investigation were carried out. R6G molecules form H-type aggregates, however with imperfect geometry causing their fluorescence. Excitation energy of the remnant monomeric R6G is transferred to aggregates in a few picoseconds. Therefore the fluorescence intensity of aggregates is much higher than the fluorescence intensity of monomers even at low aggregate concentration. New long-wavelength fluorescence band, caused by formation of larger aggregate structures emerges at very high R6G concentration, which causes decrease the overall fluorescence efficiency.

REFERENCES

[1] A. Lewkowicz, P. Bojarski, A. Synak, B. Grobelna, I. Akopova, I. Gryczyński, and L. Kułak, “Concentration-Dependent Fluorescence Properties of Rhodamine 6G in Titanium Dioxide and Silicon Dioxide Nanolayers,” J. Phys. Chem. C, vol. 116, no. 22, pp. 12304–12311, Jun. 2012.

51

P5 Ultrafast charge generation, high and balanced charge carrier mobilities in organo halide perovskite solar cell

Carlito S. Ponseca Jr.1, Mohamed Abdellah1, Kaibo Zheng1, Arkady Yartsev1, Tobjörn Pascher1, Tobias Harlang1, Pavel Chabera1, Tonu Pullerits1, Andrey Stepanov2, Jean-

Pierre Wolf2, and Villy Sundström1 1Division of Chemical Physics, Lund University, Box 124, 221 00 Lund, Sweden

2GAP-Biophotonics, University of Geneva, 22, Chemin de Pinchat, 1211 Geneva 4, Switzerland


Interest in organo halide perovskite based solar cells has increased dramatically in the past two years since it was reported to have reached an unprecedented overall power conversion efficiency of 15%; and is currently on the way of reaching 20% [1,2]. However, it’s early time dynamics has not yet been understood. Therefore, there is an urgent need to determine the nature of its initial photophysical processes which is lacking in the present literature.

Top panel of Fig. 1 is the early time kinetics of the three samples measured using time resolved THz (solid line) and transient absorption (line with symbol). For neat CH3NH3PbI3 and CH3NH3PbI3/Al2O3, the THz kinetics is characterized by an ultrafast (instrument response) rise followed by a 2 ps of further increase. This is in agreement with the two step rise in the transient absorption kinetics having identical timescales. From these traces, we conclude that charges are initially generated (instantaneous) which are Coulombically bound, that is, electron-hole pairs. An activation energy on the order of thermal energy, kT, is required before it dissociates to mobile charges, which in this case manifested as the 2 ps rise. In contrast, the rise of THz kinetics in CH3NH3PbI3/TiO2 is just one component and is limited by our instrument. Similar ultrafast rise is observed in TiO2 attached to either dye [5], or quantum dot [6], and assigned as electron injection. These studies and the favorable band alignment between the perovskite and metal oxide lead us to conclude that the injection is also ultrafast.

REFERENCES [1] J. Burschka, N. Pellet, S. J. Moon, R. Humphry-Baker, P. Gao, M. K. Nazeeruddin, M. Grätzel; Nature 499 (2013) pp. 316-319. [4] S. D. Stranks, G. E. Eperon, G. Grancini, C. Menelaou, M. J. P. Alcocer, T. Leijtens, L. M. Herz, A. Petrozza, H. J. Snaith; Science 342 (2013) pp. 341-344. [5] H. Němec, J. Rochford, O. Taratula, E. Galoppini, P. Kužel, T. Polívka, A. Yartsev, V. Sundström; Phys. Rev. Lett. 104 (2010) pp. 197401-197405. [6] K. Zidek, K. Zheng, C. Jr. S. Ponseca, M. E. Messing, L. R. Wallenberg, P. Chabera, M. Abdellah, V. Sundström, T. Pullerits; J. Am. Chem. Soc. 134 (2012) pp. 12110-12117.

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ed to

1)

Delay Time (ps)

CH3NH3PbI3

CH3NH3PbI3/Al2O3

CH3NH3PbI3/TiO 2

Fig. 1 Early time dynamics the three samples measured using THz (solid line) and transient

absorption (solid line with

52

P6 Surface plasmon dynamics in Cu containing and Ag containing diamond like carbon nanocomposite films

D. Peckus1,2, T. Tamulevičius1, Š. Meškinis1, A. Tamulevičienė1, A. Čiegis1, A. Vasiliauskas1, O. Ulčinas1, S. Tamulevičius1

1Institute of Materials Science of Kaunas University of Technology, Savanorių Ave. 271, Kaunas LT-50131, Lithuania,

2Center for Physical Sciences and Technology, Savanorių Ave. 231, Vilnius LT-02300, Lithuania, [email protected]

Recently, electron dynamics and energy relaxation processes in noble metal nanoparticles were intensively investigated. These nanomaterials can be useful for generation of ultrashort impulses, all-optical signal processing and ultrafast switching [1].

In the current research surface plasmon dynamics of Cu and Ag nanoparticles embedded in diamond like carbon (DLC) matrix [2, 3] were analyzed. DLC films (100 nm in thickness) with different metal content were synthesized employing unbalanced magnetron sputtering of metal (Cu or Ag) targets with argon ions in acetylene gas atmosphere. The size of nanoparticles and chemical composition of the films were determined employing SEM-EDS and AFM. Optical properties were analyzed with UV-VIS-NIR spectrometer while ultrafast processes - employing transient absorption spectrometer (HARPIA, Light Conversion Ltd.).

Data analysis showed that transient absorption relaxation spectra and traces are different for Ag and Cu DLC nanocomposites (Fig. 1). DLC:Cu nanocomposites demonstrate only short ground state bleaching relaxation component (~1 ps) while DLC:Ag short (~1 ps) and long (~1000 ps) components. The fast decay component can be attributed to cooling dynamics of hot electrons in Ag nanoparticles. The long-lived component of bleaching recovery most likely represents the cooling process of ‘hot’ Ag nanoparticles whose temperature is higher than that of the surrounding DLC matrix.

This research was funded by the European Social Fund under the Global Grant measure (NIRSOLIS Grant No. VP1-3.1-ŠMM-07-K-03-057).

REFERENCES [1] M. Kauranen and A. Zayats, Nature Photonics, 6, pp. 737-746 (2012). [2] T. Tamulevičius, A. Tamulevičienė, D. Virganavičius, A. Vasiliauskas, V. Kopustinskas, Š. Meškinis, S. Tamulevičius, Nuclear Instruments and Methods in Physics Research Section B, 10.1016/j.nimb.2013.09.052. [3] Š. Meškinis, A. Vasiliauskas, K. Šlapikas, G. Niaura, R. Juškėnas, M. Andrulevičius, S. Tamulevičius, Diamond and Related Materials, 40, pp. 32-37 (2013).

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0 ps 0,1 ps 0,2 ps 0,5 ps 10 ps

b

Fig. 1. Transient absorption spectra of DLC nanocomposites containing Ag (a) and Cu (b) nanoparticles. In both samples concentration of Ag or Cu is 38wt%.

53

P7 2D electronic spectroscopy of porphyrin nanorings

Eglė Bašinskaitė1, Jan Alster2, Vytautas Butkus1,3, Darius Abramavicius1, Leonas Valkunas1,3, Donatas Zigmantas2

1 Department of Theoretical Physics, Faculty of Physics, Vilnius University, Vilnius, Lithuania 2 Department of Chemical Physics, Lund University, Lund, Sweden

3 Center for Physical Sciences and Technology, Vilnius, Lithuania [email protected]

2D electronic spectroscopy (2DES) is an ultrafast optical spectroscopy technique, used to probe complex temporal dynamics of the photo-induced excitation of the system. 2DES allows the direct mapping of excitation energy transfer, quantum coherence dynamics and other phenomena of molecular systems [1].

Structural similarity with some light harvesting complexes encouraged synthesis and examination of cyclic porphyrin polymers [2,3]. Porphyrin nanoring (Fig. 1(a)) is a fully π-conjugated belt-shaped system consisting of six zinc porphyrin molecules and the hexadentate template. Spectroscopic properties of the nanoring differ significantly compared with single porphyrins or linear porphyrin polymers [4].

In this study, analysis of the energy transfer at the porphyrin nanoring using 2DES is presented. 2D spectra, measured at room (Fig. 1(b)) and cryogenic (77K) conditions, revealed the energy level structure determined by the strong vibronic coupling. Two different energy transfer processes were extracted: fast (lifetime of 200 fs) energy transfer to the lowest excited state, followed by a slower relaxation (280 ps lifetime) to the ground state. The findings are supported by numerical calculations employing the vibronic exciton model.

REFERENCES

[1] L. Valkunas, D. Abramavicius, T. Mančal; Molecular Excitation Dynamics and Relaxation, Weinheim: Wiley-VCH, 2013 [2] M. Hoffmann, C. J. Wilson et al., Angewandte Chemie International Edition 46(17) (2007) pp. 3122-3125. [3] M.C. O'Sullivan et al.; Nature 469 (2011) pp. 72–75 [4] H. L. Anderson, Chemical Communications 23 (1999) pp. 2323–2330.

Fig. 1 The structure (a) and the real part of the total 2D spectra (b) of the porphyrin

nanoring at population time t2=200 fs.

54

P8 Spectral Dynamics in Quenched Light Harvesting Antenna

Egidijus Songaila1, Ramūnas Augulis1, Erica Belgio2, Alexander Ruban2, Leonas Valkūnas1,3

1Institute of Physics of Center for Physical Sciences and Technology, A. Goštauto 11, LT-01108 Vilnius Lithuania

2School of Biological and Chemical Sciences, Queen Mary College, University of London, Mile End, Bancroft Road, London, E14NS, UK

3Theoretical Physics Department, Faculty of Physics, Vilnius University, Saulėtekio av. 9, LT-10222 Vilnius, Lithuania

[email protected]

The apparatus of light energy absorption and conversion into chemical bonds has been researched quite thoroughly. However, one of the still unanswered questions is how the photosynthetic apparatus deals with the surplus of light. Right now, the main mechanism behind the non-photochemical quenching is explained through three regulation steps: change in the pH gradient due to intense photosynthesis, through xanthophyll cycle, and the presence of the PsbS protein in the membrane. In combination, these three result in structural changes within the PSII antenna (light harvesting complex antenna, LHCII) and create dissipative electronic states. [1]

To learn about the exact molecular mechanism behind these structural changes, transient absorption and kinetic fluorescence spectroscopy experiments were performed. Temperature dependent fluorescence and absorption spectra of LHCII in quenched and unquenched states were recorded.

At low temperatures, a new fluorescence band at 700 nm appears in quenched LHCII. Kinetics of 700 nm band has different rise and decay times from that of 685 nm band, demonstrating their different origins.

REFERNCES [1] C.D.P.Duffy, L.Valkunas, A.V.Ruban Phys.Chem. Chem. Phys, 2013, 15, 18752

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Fig. 1 Temperature dependence of quenched and

unquenched LHCII fluorescence spectra.

55

P9 Exploring first principle methods for studying N,N-

dimethylaminobenzylidene-1,3-indandione excited states.

Guntars Zvejnieks, Martins Rutkis and Andrejs Jurgis

Institute of Solid State Physics, University of Latvia, Kengaraga 8, Riga LV 1063, Latvia. Email: [email protected].

The growing attention to nonlinear optical materials is supported by their potential applications in future photonic devices. A promising building block for such materials is N,N-dimethylaminobenzylidene-1,3-indandione (DMABI) asymmetric dipolar donor–acceptor molecule that demonstrates pronounced changes in the dipole moment upon photoexcitation, resulting in transformation of its optical and electrical properties.

a)

b)

Fig. 1 Ground (a) and excited (b) state DMABI molecule geometries obtained from first principle calculations, CAM-B3LYP/6-311G(dp)

DMABI was studied both experimentally and theoretically earlier [1-3], however no first principle calculations gave conclusive information regarding relaxed excited state geometry. In the present work, we explore a range of DFT functionals using different quality basis functions for excited state calculations, as well as Møller–Plesset perturbation and Coupled Cluster theories for ground state calculations. We demonstrate in Fig.1 that the twisted excited state geometry of DMABI is obtained if the long range Coulomb interaction corrections are accounted in the DFT functional, e.g., using CAM-B3LYP.

REFERENCES [1] M. Rutkis et all; Proc. of SPIE 6192 (2006) 61922Q. [2] S. Jursenas et al; Synthetic Metals 109 (2000) 169. [3] V. Gulbinas et al; J. Phys. Chem. A 103 (1999) 3969.

56

P10 Unusual 2D electronic spectroscopy signals from Peridinin

Chlorophyll a Protein.

J. Alster1,2, S. Yoo2 and D. Zigmantas2 1Department of Chemical Physics and Optics, Charles University, Ke Karlovu 3, Praha 2, CZ-121 16,

Czech Republic. 2Department of Chemical Physics, Lund University, Getingevägen 60, Lund, S-22241, Sweden.


Peridinin Chlorophyll a Protein (PCP) is a light harvest-ing antenna from dinoflagellate Amphidinium carterae [1]. PCP has an unusual pigment composition — the main light harvesting molecule is carotenoid peridinin, in contrast to the majority of other light harvesting antennas where such a function belongs to chlorophyll derivatives.

We have employed two dimensional electronic spectroscopy (2DES) to study PCP. This ultrafast, non-linear optical method gives information rich data and is usually very well suited for the study of systems with interacting chromophores. However, in case of PCP, the interpretation of the observed signals is far from trivial.

The first problem is caused by the presence of unwanted, non-resonant signals generated in the sample cell walls. We have developed a novel sample holder to mitigate these signals in low temperature measurements [2].

Several unusual signal are connected with the sample response. For example, position of oscillatory peaks connected with vibrational coherences in PCP depends on the spectrum of excitation light. Furthermore, the phase behavior of oscillatory peaks seems to mix contributions from rephasing and non-rephasing parts of the signal. These signals require a careful analysis.

REFERENCES [1] T. Polívka, R. G. Hiller, and H. A. Frank; Archives of Biochemistry and Biophysics 458 (2007) pp. 111-120. [2] S. Yoo, J. Alster, and D. Zigmantas; Review of Scientific Instruments, accepted for publication.

Fig. 1 2DES spectra of PCP reveal unusual signals.

57

P11 Femtosecond Time-Resolved Gas Phase Studies of the cis-

and trans-azobenzene radical cations.

Kristin Munkerup1, Timothy Bohinski2, Maryam Tarazkar2, Katharine M. Tibbetts2, Theis I. Sølling1 and Robert J. Levis 2

1Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark 2Department of Chemistry, Temple University, Philadelphia, PA 19122, United States


Azobenzene is of great interest within various research fields due to its ability to photoisomerize. It is evident that such a property is useful when developing photoswitches and therefore the use of azobenzene often involves introducing it to charged, solute and solid state environments. To fully comprehend the dynamics in such environments it is a good first approach to identify and understand the dynamics in the gas phase. Since the neutral dynamics have been studied extensively, we direct our attention to the cation dynamics. A previous study of trans-azobenzene shows that it is possible to probe the radical cation dynamics of the D0 state by ionizing with resonance-enhanced multiphoton ionization through (π,π*) states.1,2 Oscillations in the parent and phenyl fragment transients were observed and attributed a torsional motion between the phenyl groups.1

In this study cis- and trans-azobenzene radical cations have been prepared using strong field tunnel ionization and the dynamics investigated with femtosecond time-resolved mass spectrometry. The resulting transients (Fig. 1) reveal how the cis-azobenzene also shows oscillations and that it dissociates into the same fragments as trans-azobenzene. However, there are two important differences: the oscillations in the cis-azobenzene transients are initially phase shifted compared to those of the trans-azobenzene transients and the periods of the oscillations differ between the two isomers. These two differences are explained by inherent geometry differences between the two isomers and by the different energy gain the two isomers obtain by relaxing from the initial geometry (i.e., that of the neutral) to the equilibrium geometry of the radical cation.

REFERENCES [1] J. W. Ho, W. K. Chen, P. Y. Cheng; J Chem Phys 131 (2009) pp. 134308. [2] T. Schultz, J. Quenneville, B. Levine, A. Toniolo, T. J. Martinez, S. Lochbrunner, M. Schmitt, J. P. Shaffer, M. Z. Zgierski, A. Stolow; J Am Chem Soc 125 (2003) pp. 8098-8099

Fig. 1 Azobenzene transients of the (a) Parent fragment, (b) Phenyl fragment and (c) the Phenyldiazene fragment. The transients were recorded with a 1500-1540nm pump pulse with Ipump = 40µJ and a probe pulse of 800nm with Iprobe = 5µJ.

58

P12 Optically controlled bidirectional switching of an

indolobenzoxazine type photochromic compound

Kipras Redeckas1, Vladislava Voiciuk1, Rasa Steponavičiūtė2, Vytas Martynaitis2, Algirdas Šačkus2, and Mikas Vengris1

1Quantum Electronics Department, Vilnius University, Saulėtekio 10, LT-10223 Vilnius, Lithuania 2 Department of Organic Chemistry, Kaunas University of Technology, Radvilėnų 19, LT-50254

Kaunas, Lithuania Email: [email protected]

Photochromism is a reversible photochemi-cal reaction that results in a temporary structural change of a molecular compound along with a distinctive transformation of its absorption spectrum [1]. Photochromism of indolobenzoxazines is based on the light induced opening and thermal closing of the oxazine ring [2]. We applied femtosecond-resolution three pulse techniques to investigate the forward and backward switching capabilities of a structurally modified indolobenzoxazine compound [3]. A UV pulse was used to excite the ring-closed form, causing a C-O bond cleavage and formation of a spectrally red-shifted isomer within a timescale of ca. 100 ps. A successive, temporally delayed nIR pulse was used to reexcite the molecular system, causing a fast (<40 ps) photoinduced oxazine ring-closing, thereby “shorting-circuiting” the normally nanosecond lasting photocycle. Due to this perturbation about 6% of the reexcited state population was reverted back to the main molecular ground state. Two possible models, involving the S1 excited state of the terminal photoproduct and its hot ground state, are introduced to explain post-reexcitation photodymanics.

REFERENCES [1] N. Tamai, H. Miyasaka, Chemical Reviews 100 (2000) pp. 1875-1890. [2] M. Tomasulo, S. Sortino, A.J.P. White, F.M. Raymo, Journal of Organic Chemistry 70 (2005) pp. 8180-8189. [3] V. Voiciuk, K. Redeckas, V. Martynaitis, R. Steponavičiūtė, A. Šačkus, M. Vengris, Journal of Photochemistry and Photobiology A: Chemistry, 278 (2014) pp. 60-68.

Fig. 1 Steady state and transient absorption

spectra of the investigated compound.

Fig. 2 Time-resolved double difference

absorption (ΔΔA=ΔAPRP-ΔAPP-ΔARP) spectrum at τrepump=1 ns.

59

P13 Raman and electronic absorption spectra in Carotenoids:

A Density Functional Theory Study

Mindaugas Macernis1,2 1Theoretical Physics Department, Faculty of Physics, Vilnius University,

Saulėtekio al. 9, LT-10222 Vilnius, Lithuania. 2Center for Physical Sciences and Technology, A. Gostauto 11, LT-01108 Vilnius, Lithuania


Carotenoids (Cars) play a number of essential functions in photosynthesis such as harvesting the light in the blue-green region, where chlorophylls poorly absorb, and are involved in photoprotection of the photosynthetic apparatus. A detailed knowledge of Cars is required for an

understanding of their light-harvesting functions and, in particular, for identification of their possible role in NPQ. [1] Using quantum chemical calculations, we have modelled the Raman spectra and optical transitions of nine simple carotenoid molecules [2]. Calculations performed on simpler polyene chains with different substitutions allow us to pinpoint the molecular origin of the carotenoid properties. This led us to address the influence the carotenoid functional groups on their Raman and optical absorption spectra. Finally, as it was recently shown that polarisability had a small but significant effect on the carotenoid ground-state, we have also modelled the resonance Raman spectra and S0-S2 transitions of lutein in different solvents. The results demonstrate the linear

dependence between the frequency of the so-called ν1 band corresponding to the C=C stretching modes in the Raman spectra and the S0-S2 electronic transition for molecules of different conjugation lengths. Various relationship have been identified from the calculations. Firstly, the effective conjugation length shortens in conformers of carotenoids containing β-rings while it increases in polyene upon s-cis-isomerisation at their ends. Secondly, methyl groups connected to the conjugated chain of carotenoids induce a splitting of the ν1 band in the Raman spectra. Thirdly, the effective conjugation lengths of all-trans-polyenes and corresponding all-trans-carotenoids are the same as follows from the Raman ν1 frequency, however, they are different as defined from S0-S2 electronic transition energies. The results well correlate with the experimental observations.

REFERENCES [1] M.Macernis, J.Sulskus, C.D.P.Duffy, A.V.Ruban and L.Valkunas; J. Phys. Chem. A 40 (2012) pp. 9843-9853. [2] M.Macernis, J.Sulskus, S.Malickaja, B.Robert and L.Valkunas; J. Phys. Chem. A 10 (2014) pp. 1817-1825.

1535 1540 1545 1550 1555 1560 1565 1570 1575 15801,8

1,9

2,0

2,1

2,2

2,3

2,4

2,5

-carotene s-cis2

-carotene s-cis1

C36--carotene S0–

S2 (

eV)

1 (cm–1)

C50--carotene

spirilloxanthin (N=13)

C44--carotene

lycopene (N=11)

spheroidene (N=10)-carotene

lutein

neurosporene (N=9)

0,07 0,08 0,09 0,10 0,11 0,12

1/N

Fig. 1 Correlation between the S0–S2 electronic

transition energy and the v1 Raman band position calculated for Cars under consideration.

60

P14 Charge Separation Pathways in Dye/Fullerene Bulk-

Heterojunction Solar Cells

Ramūnas Augulis1, Domantas Peckus1, Andrius Devižis1, Dirk Hertel2, Vidmantas Gulbinas1

1Institute of Physics, Center for Physical Sciences and Technology, Savanorių. 231, LT-02300 Vilnius A. Goštauto 11, LT-01108 Vilnius Lithuania

2Department of Chemistry, Physical Chemistry, University of Cologne, Luxemburgerstr. 116, [email protected]

Organic solar cells based on bulk-heterojunction concept can potentially be competitive with the traditional silicon based solar cells. Despite the progress made during the last decade, the efficiency of organic solar cells is still not sufficiently high. This is mostly due to too many factors influencing their performance, for example: optoelectrical properties of the materials used, macroscopic design of the cell, morphology of the blend.

Here we demonstrate a detailed separation of charge carrier generation pathways by combining field-dependent time-resolved fluorescence and time-resolved second harmonic generation in a model system: merrocyanine/fullerene blends (Fig. 1). The measured timescales of the processes observed range from hundreds of femtoseconds up to microseconds. In addition, relative contributions of the pathways involved to the total efficiency of the cell are estimated.

Several interesting conclusions could be drawn from the obtained results. First, in most cases the blends are highly inhomogeneous and multiple charge separation channels contribute to the total extracted charge. Second, there is an optimum domain size and degree of percolation for the blends, for example, if the domains are too small (smaller than the Coulomb radius for the CT pairs), carriers are prone to geminate recombination, if the blends are too large – not all the excitons can reach the dye/fullerene interface.

The techniques developed for the merrocyanine/fullerene model system can be readily applied for any other bulk-heterojunction solar cells and used as a gauge of performance limiting factors.

The research was partly supported by the Lithuanian Ministry of Education and Science, project VP1-3.1-ŠMM-08-K-01-009.

Fig. 1 A schematics of the carrier separation processes in a bulk-heterojunction solar cell. 1) Diffusion of the excitons to the dye-fullerene interface. 2) Dissociation of charge-transfer states. 3) Diffusion of electrons within fullerene domains. 4) Motion of electrons between fullerene domains. 5) Motion of holes.

Fullerene

-

-

1

2

34

5

Exciton

Dye

Electron

Hole

CT Pair Cath

ode

Anod

e+

-

61

P15 Study of artificial light harvesting antennae by quantum

chemical methods

Svetlana Malickaja1, Mindaugas Macernis1,2, Juozas Sulskus1, Leonas Valkunas1,2

1Department of Theoretical Physics, Faculty of Physics, Vilnius University, Vilnius, Lithuania 2Center for Physical Sciences and Technology, Vilnius, Lithuania.


Carotenoids play a crucial role in the energy dissipation process by quenching chlorophyll singlet excited states in photosynthetic antennae. Additionally, they are also involved in the photoprotection process in green plants as quenchers of chlorophyll triplets and, thus, responsible for protection of the system from the singlet oxygen generation [1]. Artificial light-harvesting antennae are used for better understanding the details of carotenoids involved in light harvesting, energy transfer, electron transfer, and photoprotective processes [1,2]. These artificial structures are capable of performing the specific functions carried out by their natural counterparts. The experimental and theoretical investigation allows one to determine photophysical and photochemical mechanisms underlying the behaviour of the natural systems [2].

Here we present our quantum chemical study of phthalocyanine-carotenoid dyads in which a phenylamino group links phthalocyanine to carotenoids having 8–11 backbone double bonds. We analysed the structures in the ground electronic state, the dependence of electronic excitation characteristics of dyads on the conjugation length of carotenoids.

The geometry optimizations in the ground electronic state were performed using DFT with the CAM-B3LYP long-distance corrected exchange-correlation functional and the 6-31G(d,p) basis set as this method is considered to yield physically realistic geometries. Since theoretical investigation of systems containing polyene chains is known to be difficult problem itself because of the dark electronic states of carotenoids which cannot be determined by single excitation methods like TD-DFT [3], the calculation of the excited states were performed using multiconfigurational quasidegenerate perturbation theory (MC-QDPT) with general multiconfiguration (GMC) SCF wave functions as reference functions (GMC-QDPT) [4]. The results show different character of doubly excited optically dark states located between active energy levels of phtalocyanyne and carotenoids obtained for shorter dyads having 8–9 double bonds and longer dyads having 10–11 double bonds.

REFERENCES [1] R. Berera, C. Herrero, I. H. M. van Stokkum, M. Vengris, G. Kodis, R. E. Palacios, H. van Amerongen, R. van

Grondelle, D. Gust, T. A. Moore, A. L. Moore, J. T. M. Kennis, PNAS 103 (2006) pp. 5343–5348. [2] M. Kloz, S. Pillai, G. Kodis, D. Gust, T. A. Moore, A. L. Moore, R. van Grondelle, J. T. M. Kennis, J. Am. Chem.

Soc. 133 (2011) pp. 7007–7015. [3] M. Macernis, J. Sulskus, C. Duffy, A. Ruban, L. Valkunas, J Phys Chem A 116 (2012) pp. 9843–9853. [4] R. Ebisuzaki, Y. Watanabe, H. Nakano, Chem. Phys. Lett. 442 (2007) pp. 164-169.

62

P16 Electronic Properties of Indolo[3,2-b]carbazole

Compounds Revealed by Time Resolved Spectroscopy

Simona Streckaitė1, Renata Karpicz1, Alytis Gruodis2, Saulius Grigalevičius3 1Institute of Physics, Center for Physical Sciences and Technology, A.Goštauto ave. 11, LT-01108,

Vilnius, Lithuania 2Department of General Physics and Spectroscopy, Vilnius University, Saulėtekio al. 9-III,

LT-10222 Vilnius, Lithuania 3Department of Organic Technology, Kaunas University of Technology, LT-44029, Kaunas, Lithuania


Future of low-cost and easy processing optoelectronics is expected to be organic semiconductors which promise flexible devices and large area applications from solutions. For this reason organic semiconductor materials are required to be suitable for forming amorphous films with high thermal and morphological stability possessing good hole-transport, mechanical and electrochemical properties.

To comply with all the requirements, effective hole-transport materials based on indolo[3,2-b]carbazole (ICZ) are investigated. These materials have nitrogen atom in the carbazole fragment which provides electron-donating ability. Moreover because of high glass transitions temperatures, ICZ compounds provide great thermal and morphological constancy. These advantages make these compounds promising as hole transport layers in OLEDs [1, 2].

In our work, we present investigation of six newly synthesized ICZ molecules, which differ in connected functional group. The aim of this work was to ascertain differences among all studied compounds determined by connected functional group. Compounds were investigated by using steady-state and ultrafast time-resolved spectroscopy as solutions and thin films. Transient absorption measurements were performed by using femtosecond absorption pump-probe spectroscopy. Experimental data were supplemented by quantum chemical calculations performed in the framework of density functional theory (DFT).

Ultrafast diferential absorbtion showed similar relaxation of exited molecules in all investigated compounds. Charge transfer in exited state does not depend on properties or position of connected functional group.

REFERENCES [1] H. P. Zhao et al.; Structure and electronic properties of triphenylamine-substituted indolo[3,2-b]carbazole derivatives as hole-transporting materials for OLEDs, Chem. Phys. Lett. 439 (2007) pp. 132–137. [2] H. P Zhao et al.; Effect of substituents on the properties of indolo[3,2-b]carbazole-based hole-transporting materials, Org. Electron. 8 (2007) pp. 673–682.

The research was partly supported by the Lithuanian Ministry of Education and Science, project VP1-3.1-ŠMM-08-K-01-009.

63

P17 Highly efficient intrinsic phosphorescence from a

σ conjugated poly(silylene) polymer

S. Toliautas1, J. Sulskus1, A. Kadashchuk2,3, Yu. Skryshevski2, A. Vakhnin2, R. Augulis4, V. Gulbinas4,5, S. Nespurek6, J. Genoe3, and L. Valkunas1,4

1Department of Theoretical Physics, Vilnius University, Saulėtekio 9-III, LT-10222 Vilnius, Lithuania 2Institute of Physics, National Academy of Sciences of Ukraine, Prospect Nauky 46, 03028 Kyiv, Ukraine

3IMEC, Kapeldreef 75, B-3001 Leuven, Belgium 4Center for Physical Sciences and Technology, Savanorių 231, LT-02300 Vilnius, Lithuania

5Department of General Physics and Spectroscopy, Vilnius University, Saulėtekio 9-III, LT-10222 Vilnius, Lithuania

6RICE, Faculty of Electrical Engineering, University of West Bohemia, 306 14 Pilsen, Czech Republic Email: [email protected]

We have observed highly efficient intrinsic phosphorescence of a neat σ conjugated

polymer, poly[biphenyl(methyl)silylene] (PBMSi). At low temperatures, PBMSi solid films feature ~15% phosphorescence quantum yield, which is unusually high for purely organic conjugated polymers and is comparable to that of organometallic polymers.

It is shown experimentally that the phosphorescence of PBMSi originates from the radiative decay of triplets on the π-conjugated biphenyl group constituting the lowest triplet state, T1. This state is populated under the excitation of the σ-conjugated polymer backbone, i. e., with energy well below the lowest singlet excited state of the biphenyl group itself. The nature of the excited states in PBMSi is further investigated by performing quantum chemical calculations of the model compound. The calculations show that the lowest singlet excited state has charge-transfer (CT) character involving different parts of the same macromolecule. Energetically this state lies very close to the CT triplet excited state. We argue that the intramolecular CT state is responsible for the strongly enhanced intersystem crossing (ISC) in PBMSi due to the small positive CT singlet-triplet energy splitting (Fig. 1).

This study suggests a new molecular-level engineering approach for the enhancement of the ISC, enabling efficient conversion of primary excited singlets into triplets in conjugated polymers without involving heavy atom effect, while leaving the rate of radiative T1 S0 transition virtually unaffected.

Fig. 1 Enhanced intersystem crossing in PBMSi polymer leads to the efficient phosphorescence.

64

P18 Modeling of excitation transfer dynamics in the

photosynthetic FMO complex using the stochastic Schrödinger equation.

Vytautas Abramavicius1, 2, Darius Abramavicius1

1Faculty of Physics, Department of Theoretical Physics, Vilnius University, Saulėtekio 9, LT-10222 Vilnius, Lithuania

2Center for Physical Sciences and Technology, Savanorių 231, LT-02300 Vilnius, Lithuania Email: [email protected]

Recent 2D spectroscopy studies of photosynthetic aggregates revealed complex electronic and vibrational system dynamics [1]. Such experimental evidence is hard to explain using the widely used Markovian Redfield equation approach.

In our work we apply the stochastic Schrödinger equation [2] to study the excitation transfer times in the photosynthetic FMO complex. Energy transfer dynamics is investigated by calculating system populations and distributions of the excitation transfer times. The main goal of our work is to study the effect of the high frequency intra-molecular vibrational modes on the energy transfer process in the FMO aggregate, hence calculations are performed with different models of the environmental spectral density.

Excitation transfer time distributions (Fig. 1) calculated with Debye spectral density and spectral density obtained from molecular dynamics simulations (MD) do not differ qualitatively, thus it can be concluded that the system dynamics of the FMO complex is not very sensitive to the presence of the high frequency intra-molecular modes in the environmental spectral density.

REFERENCES [1] J.R. Caram, A.F. Fidler, and G.S. Engel, J. Chem. Phys. 137, 024507 (2012). [2] X. Zhong and Y. Zhao, J. Chem. Phys. 138, 014111 (2013).

Fig. 1 Excitation transfer time distributions calculated using different spectral densities.

65

P19 Vibrational relaxation within the carotenoid S1 state via high

frequency modes.

Vytautas Balevičius Jr.1, Leonas Valkunas1,2 and Darius Abramavicius1

1Faculty of Physics, Vilnius University, Sauletekio av. 9 bld.3. 2Center for Physical Sciences and Technology, Goštauto st. 11.


Carotenoids are ubiquitous pigment molecules performing several important functions in the photosynthetic systems [1]. Besides the photoprotective function of quenching the triplet excited chlorophyll and singlet oxygen, they act as additional light-harvesting pigments absorbing in the blue-green region of the spectrum. However, because of symmetry reasons, the absorption takes place not into the lowest excited state S1, but to the short-lived higher-lying state S2. This leads to a complicated intramolecular energy redistribution scheme within carotenoids.

In the transient absorption experiments, shortly after the excitation of the S2 state (on the scale of tens of femtoseconds) a strong signal attributed to the excited state absorption from the S1 state to some higher lying state Sn is observed. At early times this signal is blue-shifting and narrowing, which is attributed to the vibrational cooling of the S1 state [2].

Despite the arguments that the vibrational cooling proceeds via low frequency modes [2], a direct observation of the population of the carbon-carbon stretching modes (C-C and C=C) has been observed by means of non-linear spectroscopic techniques [3]. Therefore we propose a scheme, which takes into account both the internal conversion between the S2 and S1

states and the subsequent relaxation within the manifold of high-frequency vibrational states, and which allows us to obtain relevant transient absorption spectra, as shown in Fig. 1.

REFERENCES [1] H. R. Frank, and R. J. Codgell Photochem. Photobiol 1996, 63, 257. [2] H. H. Billsten, D. Zigmantas, V. Sundström, and T. Polívka Chem. Phys. Lett. 2002, 355, pp. 465-470. [3] T. Buckup, J. Hauer, J. Möhring, and M. Motzkus Arch. Biochem. Biophys. 2009, 483, pp. 219-223.

Fig. 1 Transient absorption spectra simulated using the

proposed model.

66

P20

Dynamics of excitonic polaron formation in molecular assemblies

Vladimir Chorošajev1, Darius Abramavicius1 1Faculty of Physics, Department of Theoretical Physics, Vilnius University, Saulėtekio 9, LT-10222

Vilnius, Lithuania Email: [email protected]

Spectroscopy studies of photosynthetic aggregates reveal evidence of exciton self-trapping – the formation of excitonic polarons. Thus a model which can include the memory effects of the environment is required.

In our work we apply the time-dependent Dirac-Frenkel variational principle using the Davydov Ansatze to study the dynamics of excitonic polaron formation in an optically excited molecular system. This approach enables us to non-perturbatively calculate the dynamics for a system coupled to a finite, yet large number of environmental phonon modes, thus accounting for arbitrary spectral densities and including specific intramolecural vibrations.

This approach effectively describes the quenching of the resonant coupling between interacting chromophores, induced by dissipative environment. It also shows that a few qualitatively different regimes of excitonic polaron formation are possible, depending on the environmental relaxation timescale.

Drawing 1: Evolution of site populations depending on the spectral density function of the environment

REFERENCES

[1] J. Sun, L.Duan and Y. Zhao, J. Chem. Phys. 138, 174116 (2012). [2] W. Forner Phys. Rev. B 53, 6291 (1996).

67

P21 Elaborating the excited state dynamics of the peridinin-

chlorophyll-a protein

Vladislava Voiciuk1, Kipras Redeckas1, Donatas Zigmantas2 and Mikas Vengris1

1Department of Quantum Electronics, Vilnius University, Saulėtekio al. 9, LT-10222 Vilnius, Lithuania 2Department of Chemical Physics, Lund University, Box 124, SE-22100 Lund, Sweden


Endeavors towards satisfactory explanation of the energy transfer pathways in peridinin-chlorophyll-a protein (PCP) confront the difficulty imposed by the particularly complex excited state dynamics. In addition to S1 state, the excited state manifold of peridinin includes intramolecular energy transfer (ICT) state, which is involved in energy transfer [1]. Separation of S1 and ICT states is complicated due to strong coupling, therefore they are referred to as a collective S1/ICT state.

We applied dispersed pump-dump-probe (PDP) spectroscopy to separate the contributions of the S1/ICT state in PCP. Dumping the stimulated emission band of ICT state with 950 nm pulse (Fig. 1) identified the coexistence of S1 and ICT states as distinct entities, which equilibrate on subpicosecond timescale.

Since very similar dynamics are typical to peridinin in solution, the excited state model of peridinin [2] was adapted in connectivity scheme, used in target analysis of the PP and PDP data (Fig. 2).

Target analysis revealed that ICT state is the predominant excitation energy transfer to chlorophyll channel, while S1 state undergoes relaxation via single pathway – by shifting its population to ICT.

REFERENCES [1] D. Zigmantas et al.; Proceedings of the National Academy

of Sciences 99 (2002) 16760-16765. [2] E. Papagiannakis et al.; J Phys Chem B 110 (2006) 512-

521.

400 500 600 700 800 900 1000-10

-5

0

5

10

15

20

0 1 2 3 4 5 6 7 8

-2

-1

0

1

Dump

A (m

OD

)

Wavelength (nm)

Pump

Pump probe Pump-dump-probe

A

(mO

D)

Delay (ps)

ICT stimulated emission

probe= 925 nm

Fig. 1 Transient spectrum of PCP at 0.5 ps with pump and dump pulses, used in experiments (top); the effect of dumping the ICT state with 950 nm (bottom).

Fig. 2 Connectivity scheme used in target analysis of PDP and PP data.

68

P22 Tailing surface traps in Sn-doped InP nanowires


Department of Chemical Physics, Lund University, Box 124, 221 00 Lund, Sweden Email: [email protected]

Charge carrier dynamics in as grown and SiO2 coated Sn-doped InP nanowires (NWs) in nitrogen (N2) and oxygen (O2) environment was investigated using time resolved photoinduced luminescence (TRPL). We interpret the excitation dependency of the NW’s PL decay as charge trapping combined with saturation of traps at high excitations. We have confirmed the trap filling effect by PL pump-probe experiment.

We attribute charge trap formation to adsorption and light-induced reduction of oxygen molecules at the NW surface. The O2 adsorption is thermally activated and thus is more efficient under high (400 nm – 3.1 eV; 1.69 eV excess energy) than under low (780 nm – 1.6 ev; 0.19 eV) photon energy excitation at the same oxygen concentration. The adsorbed oxygen anions and thus the traps can be removed leading to NW passivation under laser irradiation of as grown and SiO2 coated Sn-doped InP NWs in N2 atmosphere. The observed strong PL sensitivity to the environment gases suggests a possible application of these NWs as optochemical transducers for gas sensing.

69

P23 Electron Dynamics in photo-excited Sodium Iodide in the

gas phase

Torsten Leitner1, Franziska Buchner2, Andrea Luebcke2, Arnaud Rouzée2, Linnea Rading3, Per Johnsson3, Michael Odelius4, Hans Karlsson5, Marc Vrakking2, and Philippe Wernet1

1Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany

2 Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born- Strasse 2a, 12489 Berlin, Germany

3 Department of Physics, Lund University, PO Box 118, 221 00 Lund, Sweden 4 FYSIKUM, Stockholm University, AlbaNova, 10691 Stockholm, Sweden

5 Theoretical Chemistry, Department of Chemistry – Ångström Laboratory, Uppsala University, PO Box 518, 751 20 Uppsala, Sweden.


Based on the ground-breaking femtosecond spectroscopy experiments by A. Zewail and coworkers, the coherent electronic and nuclear wavepacket dynamics in photo-excited NaI molecules are revisited by means of sub 100 fs resolution pump-probe photoelectron spectroscopy. Time, energy and angular resolved photoelectron distributions of NaI photoexcited with several pump wave lengths have been measured. These dynamic pathways in the energy-time landscape represent a full picture of the molecular wavepacket evolution upon pumping and directly reveal features such as the coexistence of the molecule in multiple intermolecular distances at the same time, hence coherent superposition, or a transfer of wavepacket population between different molecular states. Further more, the dispersion of the evolving wavepacket and a dependence of this dispersion on the initial pump energy can be seen in the spectra. Additionally, the angular resolved picture provides deeper insight into the symmetry of the molecular electron density and their dynamics. These measurements are compared to state of the art, molecular quantum dynamics simulations (non angular resolved) in order to better interpret the measurements as well as to explore the computational reproducibility of fundamental dynamic processes in nature and to test the current models and theories.

70

P24 From ultrafast events to equilibrium – uncovering the

unusual dynamics of ESIPT reaction: the case of dually fluorescent diethyl-2,5-(dibenzoxazolyl)-hydroquinone.

Paweł Wnuk1,4, Gotard Burdziński2, Michel Sliwa3, Michał Kijak1, Anna Grabowska1, Jerzy Sepioła1, Jacek Kubicki2

1Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland

2Faculty of Physics, Adam Mickiewicz University in Poznań, Umultowska 85, 61-614 Poznań, Poland 3Laboratory of Infrared and Raman Spectroscopy UMR 8516/CNRS Lille University, Lille, France

4Faculty of Physic, University of Warsaw, Hoża 69, 00-681 Warsaw, Poland Email: [email protected]

The excited state intramolecular proton transfer (ESIPT) reaction of the dually fluorescent 2,5-diethyl-(dibenzoxazolyl)-hydroquinone (DE-BBHQ) was studied with several time resolved techniques. The complementary character of up-conversion and time correlated single photon counting methods was demonstrated. According to the up-conversion experiments, the primary excited dienol form transforms into the monoketo tautomer in a very efficient ultrafast (~100 fs) proton transfer reaction [1]. The reverse process of proton transfer repopulating the excited dienol form was also observed, whose rate strongly depends on solvent polarity. Both contributions of dienol emission were univocally distinguished. The double-well potential of the S1 state of DE-BBHQ was calculated, and the nature of the phototautomer as the monoketo form was confirmed. This represents an example of how to combine different experimental methods with different temporal resolutions for unravelling ultrafast proton transfer reaction. A similar experimental strategy can be easily adopted for other systems where equilibrium between two states is observed (e.g. photoinduced electron or energy transfer).

REFERNCES [1] P. Wnuk, G. Burdziński, M. Sliwa, M. Kijak, A. Grabowska, J. Sepioł and J. Kubicki, Phys. Chem. Chem. Phys., 16, 2542-2552 (2013)

Fig. 1. The two partners of ultrafast ESIPT reaction of DE-BBHQ reach the equilibrium which strongly depends on solvent

polarity.

71

P25 Ultrafast TRIR and fluorescence measurements of excited

state proton transfer in anils

Piotr Skibiński1,2, Paweł Wnuk1,2, Jacek Waluk2 and Czesław Radzewicz1,2

1Physics Department, University of Warsaw, Hoża 69, Warsaw, Poland

2Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw, Poland Email: [email protected]

We present our recently developed time-resolved infrared transient absorption spectrometer. The optical setup is built with a high repetition rate (150 kHz) light source based on Ti:sapphire oscillator, regenerative amplifier and nonlinear stages for generating tunable infrared probe and ultraviolet pump pulses. The available probing wavelengths cover the range between 2.4 and 10.5 μm – from hydrogen vibrations to so called fingerprint region. The pump pulse is a second harmonic (λ = 393 nm) of the source.

In the setup a new home-built compact infrared camera with two-dimensional focal plane array based on a HgCdTe semiconductor alloy has been introduced [1]. The camera is sensitive in the range of 1.7 – 10.5 μm. It allows to employ a novel detection scheme – measuring 3 different spectra derived from the same infrared source simultaneously. The scheme allows to gather information about the transient and stationary absorption spectra of a sample in the same optical setup and relate one to the other during a single measurement. The camera presents a great improvement over solutions used in similar setups [2]. The commonly achievable instrument sensitivity is close to 20 μOD (RMSE).

The spectrometer capabilities are illustrated with selected transient absorption measurements of anils and their boranil counterparts (Fig. 1) [3]. Together with complementary time-resolved fluorescence measurements performed in our laboratory we show the evidence of ultrafast excited state intramolecular proton transfer phenomenon.

REFERENCES

[1] P. Skibiński and C. Radzewicz, J. Electron. Imaging, 22(4), 043020 (2013). [2] M. Towrie et al., Applied Spectroscopy, 57(4), 367-380 (2003). [3] D. Frath et al., Organic Letters, 13(13), 3414-3417 (2011).

Fig. 1 Investigated class of molecules.

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P26 Energy Transfer in Plant Light-Harvesting Complex II

Revealed by Room-Temperature 2D Electronic Spectroscopy

Petar H. Lambrev1,2*, Kym L. Wells1, Zhengyang Zhang1, Győző Garab2 and Howe-Siang Tan1

1 Nanyang Technological University, Singapore

2 Hungarian Academy of Sciences, Biological Research Centre, Szeged, Hungary Email: [email protected], Tel. +36 62 599 600 (492)

Two-dimensional electronic spectroscopy (2DES), like the pump-probe absorption spectroscopy, is a valuable tool to monitor the excited state dynamics in systems of coupled chromophores. While both methods can identify molecular excited states based on their spectral properties and population dynamics, only 2DES provides separate spectral information about the donor and acceptor molecules involved in energy transfer. This makes it especially powerful in disentangling the energy transfer network in multichromophore systems such as light-harvesting complexes. Pump-geometry 2DES utilizing phase cycling was performed at room temperature on isolated trimeric plant light-harvesting complex II (LHCII). The time-dependent 2D spectra reveal cross peaks representing energy transfer from Chl b to Chl a and within the Chl a exciton manifold, occuring on time scales from <300 fs to >10 ps. Global lifetimes analysis of the 2DES produced 2D decay-associated spectra (2D DAS) whereby separate Chl b pools coupled to the bulk Chl a exciton states can be distinguished. These energy transfer components occur with lifetimes in the range of 0.3-3 ps. Rapid (0.3 ps) energy transfer from high-energy Chl b exciton states to the lowest-energy Chl a exciton states is observed. An indirect energy transfer pathway via an intermediate Chl a/b exciton state is also clearly resolved in the 2D DAS. This intermediate state is rapidly populated from low-energy Chl b states and has a long (several ps) lifetime due to weak coupling to the low-energy Chl a excitons. The 2D DAS reveal Chl a equilibration on a time scale of few ps. A more detailed kinetic scheme was obtained with the help of spectro-temporal model. The experimentally resolved kinetics scheme generally agrees with and adds further details to published structure-based excitonic models and spectroscopic results.

This work was supported by a grants from the Hungarian National Innovation Office, A*STAR Singapore (A*STAR SERC 102-149-0153; NIH-A*STAR TET_10-1-2011-027) and the Hungarian Scientific Research Fund (OTKA-PD 104530).

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P27 Bimolecular Photoinduced Electron Transfer Beyond the

Diffusion Limit: The Rehm-Weller Experiment Revisited with Femtosecond Time-Resolution

Arnulf Rosspeintner1, Gonzalo Angulo2, Eric Vauthey*1

1 Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1211, Genčve 4, Switzerland

2 Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland


To access to the intrinsic, diffusion free, rate constant of bimolecular photoinduced electron transfer reactions, fluorescence quenching experiments have been performed with 14 donor/acceptor pairs, covering a driving-force range going from 0.6 to 2.4 eV, using steady-state and femtosecond time-resolved emission, and applying a diffusion-reaction model that accounts for the static and transient stages of the quenching for the analysis. The intrinsic electron transfer rate constants are up to two orders of magnitude larger than the diffusion rate constant in acetonitrile. Above ca. 1.5 eV, a slight decrease of the rate constant is observed, pointing to a much weaker Marcus inverted region than those reported for other types of electron transfer reactions, such as charge recombination. Despite this, the driving force dependence can be rationalized in terms of Marcus theory.1

REFERENCES

[1] Bimolecular Photoinduced Electron Transfer Beyond the Diffusion Limit: The Rehm−Weller Experiment Revisited with Femtosecond Time Resolution. Arnulf Rosspeintner, Gonzalo Angulo, Eric Vauthey Journal of the American Chemical Society, 2014, 136 ,2026.

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List of Participants

Vytautas Abramavicius

Faculty of Physics, Department of Theoretical Physics, Vilnius University, Saulėtekio 9, LT-10222 Vilnius, Lithuania [email protected] Jan Alster Department of Chemical Physics and Optics, Charles University, Ke Karlovu 3, Praha 2, CZ-121 16, Czech Republic. [email protected] Ramūnas Augulis Institute of Physics, Center for Physical Sciences and Technology, Savanorių. 231, LT-02300 Vilnius A. Goštauto 11, LT-01108 Vilnius Lithuania [email protected] Jukka Aumanen

Nanoscience Center, Department of Chemistry, University of Jyväskylä, Finland [email protected] Eglė Bašinskaitė Department of Theoretical Physics, Faculty of Physics, Vilnius University, Vilnius, Lithuania [email protected] Vytautas Balevičius Jr. Faculty of Physics, Vilnius University, Sauletekio av. 9 bld.3., LT-10222 Vilnius, Lithuania [email protected] Oleksandr Boiko Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania [email protected] Tobias Brixner Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland,97074 Würzburg, Germany [email protected] Jevgenij Chmeliov Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio Ave. 9, Vilnius, Lithuania [email protected] Vladimir Chorošajev

Faculty of Physics, Department of Theoretical Physics, Vilnius University, Saulėtekio 9, LT-10222 Vilnius, Lithuania [email protected]

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Andrius Devižis

Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania [email protected] Jakub Dostál Department of Chemical Physics, Lund University, P.O.Box 124, 221 00 Lund, Sweden [email protected] Angela Eckstein

Center for Physical Sciences and Technology, A.Gostauto 11,LT-01108 Vilnius. [email protected]

Arvi Freiberg

Institute of Physics, University of Tartu, 142 Riia St., Tartu 51014, Estonia [email protected] Andrius Gelzinis

Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio 9-III, 10222 Vilnius, Lithuania [email protected] Thorsten Hansen Department of Chemistry, University of Copenhagen Universitetsparken 5, DK 2100 Copenhagen Ø, Denmark [email protected] Tobias Harlang

Lund University, Dep. Of Chemical Physics 22100 Lund, Sweden [email protected] Andrius Jurgilaitis

Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden [email protected] Aivaras Kazakevičius

Center for Physical Sciences and Technology, Goštauto 11, Vilnius [email protected] Søren Rud Keiding Department of Chemistry, Aarhus University, Langelandsgade 140, DK 8000 Aarhus C, Denmark [email protected] Kasper S. Kjær

Centre for Molecular Movies, Danish Technical University, Physics Department, 2800, Lyngby, Denmark [email protected]

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Liv B. Klein

Department of Chemistry, University of Copenhagen,

Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark [email protected] Nils Krebs Dept. of Physics and Astronomy, Uppsala University Box 516, SE-75120 UPPSALA, Sweden [email protected] Arne Kristoffersen

Department of physics and technology, University of Bergen [email protected] Martin. A. B. Larsen Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark [email protected] Heli Lehtivuori Nanoscience Center, Department of Biological and Environmental Sciences, University of Jyväskylä, P. O. Box 35, 40014 Jyväskylä, Finland [email protected] Torsten Leitner

Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany [email protected] Mindaugas Macernis Theoretical Physics Department, Faculty of Physics, Vilnius University, Saulėtekio al. 9, LT-10222 Vilnius, Lithuania [email protected] Svetlana Malickaja Department of Theoretical Physics, Faculty of Physics, Vilnius University, Vilnius, Lithuania [email protected] Miroslav Menšík Institute of Macromolecular Chemistry, Academy of Sceinces of the Czech Republic, Heyrovský Sq. 2, 162 06 Prague 6, Czech Republic [email protected] Kristin Munkerup Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark [email protected] Satu Mustalahti Nanoscience Center, Departments of Chemistry and Physics, P.O. Box 35, FI-40014 University of Jyväskylä, Finland [email protected]

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Jakob Brun Nielsen

Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Århus C [email protected] Michael Odelius Department of Physics, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden [email protected] David Paleček

Department of chemical physics, Lund University, P.O. Box 124, SE-22100 Lund, Sweden [email protected] Domantas Peckus Institute of Materials Science of Kaunas University of Technology, Savanorių Ave. 271, Kaunas LT-50131, Lithuania [email protected] Carlito S. Ponseca Division of Chemical Physics, Lund University, Box 124, 221 00 Lund, Sweden [email protected] Vytenis Pranculis Center for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania [email protected] Jana Preclíková

Department of Physics and Technology, University of Bergen, N-5007 Bergen, Norway [email protected] David Rais Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Heyrovského nám. 2, 162 06, Prague 6, Czech Republic. [email protected] Olga Rancova Department of Theoretical Physics, Vilnius University, Sauletekio av. 9, Vilnius, Lithuania [email protected] Kipras Redeckas Quantum Electronics Department, Vilnius University, Saulėtekio 10, LT-10223 Vilnius, Lithuania [email protected] Joachim Seibt Department of Chemical Physics, Lund University, Box 124, SE-21000,Lund, Sweden [email protected]

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Almis Serbenta Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747 AG, Netherlands. [email protected] Egidijus Songaila Institute of Physics of Center for Physical Sciences and Technology, A. Goštauto 11, LT-01108 Vilnius Lithuania [email protected] Simona Streckaitė Institute of Physics, Center for Physical Sciences and Technology, A.Goštauto ave. 11, LT-01108, Vilnius, Lithuania [email protected] Stepas Toliautas

Department of Theoretical Physics, Vilnius University, Saulėtekio 9-III, LT-10222 Vilnius, Lithuania [email protected] Erling Thyrhaug Department of Chemical Physics, Lund University, Getingevägen 60, 22241 Lund, Sweden [email protected] Mikas Vengris Quantum Electronics Dept., Faculty of Physics, Vilnius University, Saulėtekio 10, LT1022 Vilnius, Lithuania [email protected] Vladislava Voiciuk Department of Quantum Electronics, Vilnius University, Saulėtekio al. 9, LT-10222 Vilnius, Lithuania [email protected] Jacek Waluk

Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44, 01-224 Warsaw, Poland [email protected] Wei Zhang Department of Chemical Physics, Lund University, Box 124, 221 00 Lund, Sweden [email protected] Kaibo Zheng Department of Chemical Physics, Lund University, Box 124, 22100, Lund, Sweden [email protected]

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Karel Žídek Department of Chemical Physics, Lund University, Getingevägen 60, 22241 Lund, Sweden. [email protected] Donatas Zigmantas Department of Chemical Physics, Lund University, P. O. Box 124, 221 00 Lund, Sweden [email protected] Guntars Zvejnieks Institute of Solid State Physics, University of Latvia, Kengaraga 8, Riga LV 1063, Latvia. [email protected] Paweł Wnuk Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland [email protected] Piotr Skibiński Physics Department, University of Warsaw, Hoża 69, Warsaw, Poland [email protected] Gonzalo Angulo Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland [email protected] Petar H. Lambrev Hungarian Academy of Sciences, Biological Research Centre, Szeged, Hungary [email protected]

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11th Nordic Femtochemistry Conference Vilnius – Lithuania