Dynamics of excitation transfer in solution: short range reactive and caging effects

In this paper, we analyze the kinetics of excitation transfer when short-range effects due to an additional reactive interaction (exchange) and to solvent cage perturbations of the relative molecular motion are introduced. We show that the short-range solvent caging influence on the observable transfer length can be brought to direct observation only in reactive systems undergoing fast molecular motion (slow reaction limit). In contrast, considering resonant electronic excitation transfer, a strong exchange mechanism (slow diffusion regime) is required to optimize its efficiency in the competition with the long-range dipolar potential. In this case, we show how to measure the range and the frequency factor of the exchange interaction, which are usually unknown parameters.