Adiabatic electron transfer in polar media

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Abstract
The rate of electron transfer in polar media is calculated in the framework of the transition state theory. It is shown that this theory is valid if k B T > (hω0/2π), where ω0 is the frequency of a particle motion at the barrier top. The pre-exponential factor of the rate constant is found to be dependent on the reaction heat, dielectric loss spectrum, ϵ(ω), and the nondiagonal matrix element, Г. The rate constant of charge transfer in water, with allowance for the resonance absorbtion region, is determined. The influence of the motion of the water complexes on the rate constant is considered and it is shown that the pre-exponential factor depends not only on the frequency of the complex vibrations, but also on its reorganization energy. The maximum value of the complex reorganization energy is calculated under the conditions where the theory is valid. In the particular case of the Debye dielectric loss spectrum the multidimensional activated complex theory is shown to be equivalent to the stochastic Alexandrov-Zusman's model and the Kramers' theory (the case of large viscosity). It is pointed out that the transition state theory allows the inertial degrees of freedom to be taken into account for a real dielectric loss spectrum, ϵ(ω).

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