Variation of the Resonant Transfer Rate When Passing from Nonadiabatic to Adiabatic Electron Transfer

Abstract

Two competing theories are used for bridging the gap between the nonadiabatic and the deeply adiabatic electron transfer between symmetric parabolic wells. For the high friction limit, a simple analytic interpolation is proposed as a reasonable alternative to them, well-fitted to the results of numerical simulations. It provides a continuous description of the electron transfer rate in the whole range of variation of the nonadiabatic coupling between the diabatic states. For lower friction, the original theories are used for the same goal. With an increase in coupling, the cusped barrier transforms into the parabolic one. Correspondingly, the pre-exponent of the Arrhenius transfer rate first increases with coupling, then levels off approaching the "dynamic solvent effect" 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 dependence of the total transfer rate. When approaching the contact distance, the exact rate becomes smaller than in the theory of dynamical solvent effects and much smaller than predicted by perturbation theory (golden rule), conventionally used in photochemistry and electrochemistry.

On the Coherent Description of Diffusion‐Influenced Fluorescence Quenching Experiments II: Early Events

“…The validity is therefore limited by the requirement that the effective coupling matrix element, V eff ðrÞ ¼ VðrÞ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi expðSÞS n =n! p , must not exceed k B T. [28] Beyond this limit, the barrier region is more parabolic than cusp, and Kramers expression for solvent-controlled electron transfer [29] is more applicable. Furthermore, the reduction of the barrier height by the strong coupling is then no longer negligible.…”

The Rehm–Weller Experiment in View of Distant Electron Transfer

“…[54][55][56] This so-called "dynamic solvent effect" is accounted for by including t L , the longitudinal relaxation time of the solvent polarisation. [57] The reaction probability for the electron transfer, w(r), is then given by [30] wðrÞ ¼…”

Ascorbic acid may not be involved in cryptochrome-based magnetoreception

“…This scenario is characterized by weak electronic coupling and the absence of appreciable solvent friction, i.e. it belongs to the domain of diabatic electron transfer [49]. In the Marcus normal region, which is applicable here, the intrinsic rate of electron transfer, w(r), is given by [50,51]   The relevance of the electron transfer reaction for the operation of cryptochrome as a magnetic compass sensor depends on whether the reaction is fast compared to the spin dynamics in the radical pair.…”