EXPERIMENTAL AND THEORETICAL-STUDIES OF FEMTOSECOND TIME-RESOLVED 3-DIMENSIONAL SPECTRA OF PHOTOSYNTHETIC REACTION CENTERS

In this Letter, we report the three-dimensional experimental and calcu lated fs transient spectra of initial electron transfer in the bacteri al reaction center of Rhodobacter sphaeroides. The wavelength-dependen t time constants are discussed. The theoretical model invokes multiple states, which are made up of lower and upper excitonic states of the dimer P. The electron transfer rates are calculated using a multi-mode system utilizing the saddle-point approximation. We find that the wav elength-dependent time constants observed experimentally can be modell ed in terms of a multi-step electron transfer mechanism.