DYNAMICS OF FAST OPTICAL BAND-SHAPE TIME EVOLUTION OF 3-CENTER ELECTRON-TRANSFER SYSTEMS

We provide here a simple description of the coherent time evolution of a coordinate point or configuration distribution on an excited state potential energy surface, following excitation by a classical delta-li ke pulse. The configuration is probed by another delta-like pulse at a later time. The time evolution of the probe pulse absorption follows patterns which depend in characteristic ways on the probability of tra nsition to other surfaces crossing the surface primarily excited, the frequency of the exciting light, and the friction of motion on the pot ential surfaces. The formalism is analytical and appropriate for use o n the primary ultrafast charge separation involving special pair and a uxiliary bacteriochlorophyll and bacteriopheophytin in the bacterial p hotosynthetic reaction center. In this respect the formalism also offe rs clues to the high-energy superexchange or low-energy coherently pop ulated nature of the intermediate state chlorophyll.