Coherent nuclear dynamics at room temperature in bacterial reaction centers. |
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| Authors: | M H Vos M R Jones C N Hunter J Breton J L Martin |
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| Affiliation: | Laboratoire d''Optique Appliquée, Ecole Polytechnique-Ecole Nationale Supérieure de Techniques Avancées, Palaiseau, France. |
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| Abstract: | A room-temperature study is reported of the femtosecond spectral evolution of the stimulated emission band of the primary electron-transfer precursor P* in bacterial photosynthesis. The study was performed with membranes of the antenna-deficient RCO1 mutant of Rhodobacter sphaeroides. A time-dependent red shift, reflecting nuclear motion out of the Franck-Condon region of the excited state, is resolved. Analysis of oscillatory features persisting for > 1 ps in the kinetics revealed main frequencies of the activated motions at 30, 84, 145, and 192 cm-1. The oscillations occur on the time scale of primary electron transfer. Our results set a lower limit for the vibrational dephasing time in P* that is not compatible with the usual assumption in theoretical treatments of complete vibrational relaxation prior to electron transfer, even at room temperature. |
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