FREE-ENERGIES OF ELECTRON-TRANSFER

A simple class of Hamiltonian models of electron-transfer systems in analyzed. We focus on the activation free energy governing the charge transfer, and especially the role of fast solvent electronic polarization. The analysis of the free energy is carried out exactly and also by a self-consistent mean field approximation that has been used in this context. Comparison with the exact analysis in the limit that the solvent electronic polarization is much faster than the time scale of the transferring electron indicates that the predictions of the mean field approximation are generally erroneous. The correct activation free energy is in agreement with traditional estimates.