Effects of intramolecular vibrations on excitation energy transfer dynamics of the Fenna-Matthews-Olson complex

Abstract

The role of vibrational coherence in photosynthetic pigment-proteins has been controversial. The present article investigates theoretically how the intramolecular vibrations of bacteriochlorophyll (BChl) influence the excitation energy transfer (EET) dynamics in the Fenna-Matthews-Olson complex (FMO). To this end, we use an exciton model incorporating recent experimental data and treat the vibrations as both coherent and incoherent. We simulate the transfer phenomena numerically with non-Markovian quantum dynamics. Our results at 300 K indicate that incoherent vibrations can moderately improve the efficiency of EET between FMO and a reaction center. With a vibronic model, we show that the coherent vibrations in either strongly or resonantly coupled BChl pairs can generate characteristic oscillations in their electronic populations which persist for several picoseconds even at 300 K. Despite such robust coherences, no significant improvement in the efficiency of EET is observed.