''False tunneling'' and multirelaxation time nonexponential kinetics of electron transfer in polar glasses

Classical electron transfer in polar glasses is described by a theory based on a model microscopic Hamiltonian which includes the discreteness and randomness of the glassy polar modes with distinct orientation. When configurational dynamics is fast, the reaction is described by exponential kinetics with a rate constant of non-Arrhenius type. The temperature dependent rate constant resembles the tunneling rate, despite the classical transfer of the electron. This effect is called ''false tunneling.'' In this limit the possibility of a self-acceleration of the reaction is pointed out. When configurational dynamics is very slow the reaction kinetics are nonexponential with multirelaxation time behavior. The reaction is shown to be almost insensitive to temperature change pointing out on a possible explanation of a broad temperature-independent range in the ''rate constant'' in an electron transfer in cytochrome c oxidation in chromatium. At short times, the reaction accelerates compared to the exponential behavior, while at long times it becomes slower. For strongly exothermic reactions the kinetics are always slower than an exponential decay. (C) 1996 American Institute of Physics.