| Abstract
| - Two competing theories are used for bridging the gap between the nonadiabatic and the deeply adiabaticelectron transfer between symmetric parabolic wells. For the high friction limit, a simple analytic interpolationis proposed as a reasonable alternative to them, well-fitted to the results of numerical simulations. It providesa continuous description of the electron transfer rate in the whole range of variation of the nonadiabaticcoupling between the diabatic states. For lower friction, the original theories are used for the same goal. Withan increase in coupling, the cusped barrier transforms into the parabolic one. Correspondingly, the pre-exponentof the Arrhenius transfer rate first increases with coupling, then levels off approaching the “dynamic solventeffect” plateau but finally reduces reaching the limit of the adiabatic Kramers theory for the parabolic barrier.These changes proceeding with a reduction in the particle separation affect significantly the spatial dependenceof the total transfer rate. When approaching the contact distance, the exact rate becomes smaller than in thetheory of dynamical solvent effects and much smaller than predicted by perturbation theory (golden rule),conventionally used in photochemistry and electrochemistry.
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