Theory of simple electron transfer reactions in a damped dielectric continuum solvent

Abstract

Electron transfer reactions in polar media have been investigated theoretically with the aid of a dielectric continuum representation of the solvent. In the quantum mechanical and statistical mechanical treatments, in particular, this dielectric continuum representation assumes a non-damped harmonic oscillator form. In general, within the entire system every subsystem which contributes to the activation process necessary to the electron transfer requires a certain energy. Typically, though, detailed knowledge of which systems participate is limited only to a few of these. The remaining subsystems still participate; the neglect of their contribution leads to inaccurate expressions for the rate constant expressions. Nevertheless, in many interesting systems one, or at worst a few, identifiable subsystems may play the predominate role in the activation process. When this is the case, it is possible to account for the remaining less well defined contributions to activation in a phenomenological manner. This is done through the introduction of a dissipation quantity, a damping constant. This paper reports the results of an investigation of the effect of both general state damping (attenuation of the transition state) and damping of individual dielectric continuum (Boson) modes on the rate of electron transfer reactions in polar media.