VIBRATIONAL COHERENCE IN BACTERIAL REACTION CENTERS - SPECTROSCOPIC CHARACTERIZATION OF MOTIONS ACTIVE DURING PRIMARY ELECTRON-TRANSFER

Coherent dynamics during the primary electron transport reaction in ba cterial reaction centers was studied. We analyzed the spectral depende nce of oscillatory features in multicolour optical pump-probe measurem ents in the spectral region of both the stimulated emission of the P reactant state and the absorption of the bacteriochlorophyll monomers . In the latter region, the manifold of activated modes gives rise to a very complex oscillatory pattern. Using simple schemes of spectrosco pic probing of wave packet dynamics on the P potential energy surfac e, the origin of the coherences is discussed. In addition to transitio ns probing P directly, electrochromic shifts of the B bands induced by oscillating charges may contribute to the signal. (C) 1998 Elsevier Science B.V. All rights reserved.