Optical dephasing and excited state dynamics in photosynthetic pigment-protein complexes

Abstract

Accumulated photon echo experiments were performed on the Fenna-Matthews-Olson pigment-protein complex which contains 21 bacteriochlorophyll (BChl) a-molecules in a well-defined configuration. The photon echo decay is extremely fast at shor-wavelength excitation in the Q y band of the BChl a-molecules, but slows down by more than two orders of magnitude with excitation at longer wavelengths. These results, and the temperature dependence of the decay, are interpreted in terms of phonon-assisted relaxation within the manifold of exciton states in the lowest excited singlet state of the complex.