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Donatas Zigmantas. Portrait.

Donatas Zigmantas

Professor

Donatas Zigmantas. Portrait.

Unraveling the nature of coherent beatings in chlorosomes.

Author

  • Jakub Dostal
  • Tomáš Mančal
  • František Vácha
  • Jakub Pšenčík
  • Donatas Zigmantas

Summary, in English

Coherent two-dimensional (2D) spectroscopy at 80 K was used to study chlorosomes isolated from green sulfur bacterium Chlorobaculum tepidum. Two distinct processes in the evolution of the 2D spectrum are observed. The first being exciton diffusion, seen in the change of the spectral shape occurring on a 100-fs timescale, and the second being vibrational coherences, realized through coherent beatings with frequencies of 91 and 145 cm(-1) that are dephased during the first 1.2 ps. The distribution of the oscillation amplitude in the 2D spectra is independent of the evolution of the 2D spectral shape. This implies that the diffusion energy transfer process does not transfer coherences within the chlorosome. Remarkably, the oscillatory pattern observed in the negative regions of the 2D spectrum (dominated by the excited state absorption) is a mirror image of the oscillations found in the positive part (originating from the stimulated emission and ground state bleach). This observation is surprising since it is expected that coherences in the electronic ground and excited states are generated with the same probability and the latter dephase faster in the presence of fast diffusion. Moreover, the relative amplitude of coherent beatings is rather high compared to non-oscillatory signal despite the reported low values of the Huang-Rhys factors. The origin of these effects is discussed in terms of the vibronic and Herzberg-Teller couplings.

Department/s

  • Chemical Physics

Publishing year

2014

Language

English

Publication/Series

Journal of Chemical Physics

Volume

140

Issue

11

Document type

Journal article

Publisher

American Institute of Physics (AIP)

Topic

  • Atom and Molecular Physics and Optics

Status

Published

ISBN/ISSN/Other

  • ISSN: 0021-9606