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Long-lived coherent oscillations of the femtosecond transients in cyanobacterial photosystem I
Authors:Sarkisov Oleg M  Gostev Fedor E  Shelaev Ivan V  Novoderezhkin Vladimir I  Gopta Oxana A  Mamedov Mahir D  Semenov Alexey Yu  Nadtochenko Victor A
Institution:N N Semenov Institute of Chemical Physics, Russian Academy of Sciences, Kosigin str 4, Moscow, Russia.
Abstract:The pulsed excitation of electronic levels coupled to specific nuclear modes by a 26 fs laser pulse at 706 nm creates a wavepacket in the nuclear space of photopystem I (PS I) of Synechocystis sp. strain PCC 6803 both in the ground state and in the one-exciton manifold. Fourier transform of transient decay curves shows several low frequency peaks. The most prominent Power Spectral Density (PSD) peaks are at omega = 49 cm(-1) and omega = 88 cm(-1). The peculiarity of the coherent wavepacket in the PS I of S. sp. strain PCC 6803 is the unique, long-lived 49 cm(-1) and 88 cm(-1) oscillations with decay times up to 10 ps. It was suggested that such a long-lived coherence is determined by a contribution of the ground state wavepacket. The dependence of these two PSD peaks on the probe wavelength resembles the profile of the transient absorption spectra of PS I. The pump-probe signal in the Soret region reflects the dynamics of the ground state wavepacket created by pulsed excitation of the Q(y)-band. It was shown that the multimode Brownian oscillator model allows a quantitative fit of the oscillatory patterns of the pump-probe signal to be obtained.
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