ANALYTICAL TREATMENT OF NONEXPONENTIAL ELECTRON-TRANSFER COUPLED TO INTRAMOLECULAR AND MEDIUM MODES

A many-mode model for electron transfer is developed. The electron tra nsfer is coupled to the classical solvent dynamics and to a molecular subsystem, consisting of many internal modes which form a dense manifo ld of states for electron transfer in the inverted region. The fluctua tions of the solvent coordinate are treated as an uncorrelated stochas tic process. For the limit of slow fluctuations it is shown that a tra nsition from a solvent-controlled transfer to a solvent-independent on e occurs as a function of the free energy of reaction. The mode predic ts a nonexponential electron-transfer kinetics of the intermediate reg ion.