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Title: Unraveling the nature of coherent beatings in chlorosomes

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{sup −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 themore » 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
Authors:
 [1] ;  [2] ; ;  [3] ;  [4] ;  [1]
  1. Department of Chemical Physics, Lund University, P.O. Box 124, SE-22100 Lund (Sweden)
  2. (Czech Republic)
  3. Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague (Czech Republic)
  4. Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice (Czech Republic)
Publication Date:
OSTI Identifier:
22253425
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; AMPLITUDES; BACTERIA; COUPLINGS; DIFFUSION; ENERGY TRANSFER; EXCITED STATES; GROUND STATES; OSCILLATIONS; SHAPE; SPECTRA; SPECTROSCOPY; STIMULATED EMISSION; SULFUR