Energy gap law for electron transfer rates in polymer glasses

Energy gap dependence of the electron transfer rate in a system with two distinct classical relaxation modes is discussed. It is shown that when the relaxation slows down, only the fast mode determines the width of the gap-law curve while the position of the maximum is related to the full reorganization energy and does not change. Frozen relaxation leads to saturation of the rate constant with respect to an increase in the electronic coupling.