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Unraveling the nature of coherent beatings in chlorosomes.

Dostal, Jakub LU ; Mančal, Tomáš; Vácha, František; Pšenčík, Jakub and Zigmantas, Donatas LU (2014) In Journal of Chemical Physics 140(11).
Abstract
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... (More)
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. (Less)
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organization
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Contribution to journal
publication status
published
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in
Journal of Chemical Physics
volume
140
issue
11
publisher
American Institute of Physics
external identifiers
  • pmid:24655205
  • wos:000334168400044
  • scopus:84897891510
ISSN
0021-9606
DOI
10.1063/1.4868557
language
English
LU publication?
yes
id
d9f43d4e-cc74-47fc-a13e-02618e399e1e (old id 4382908)
date added to LUP
2014-05-07 16:57:42
date last changed
2017-09-03 03:19:00
@article{d9f43d4e-cc74-47fc-a13e-02618e399e1e,
  abstract     = {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.},
  articleno    = {115103},
  author       = {Dostal, Jakub and Mančal, Tomáš and Vácha, František and Pšenčík, Jakub and Zigmantas, Donatas},
  issn         = {0021-9606},
  language     = {eng},
  number       = {11},
  publisher    = {American Institute of Physics},
  series       = {Journal of Chemical Physics},
  title        = {Unraveling the nature of coherent beatings in chlorosomes.},
  url          = {http://dx.doi.org/10.1063/1.4868557},
  volume       = {140},
  year         = {2014},
}