Vibrational coherence in bacterial reaction centers: spectroscopic characterisation of motions active during primary electron transfer Original Research Article

Coherent dynamics during the primary electron transport reaction in bacterial reaction centers was studied. We analyzed the spectral dependence of oscillatory features in multicolour optical pump–probe measurements 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 spectroscopic probing of wave packet dynamics on the P* potential energy surface, the origin of the coherences is discussed. In addition to transitions probing P* directly, electrochromic shifts of the B bands induced by oscillating charges may contribute to the signal.