Intramolecular vibrational excitations accompanying solvent-controlled electron transfer reactions

The theory of dynamic solvent effects on outer-sphere electron transfer (ET) was extended to incorporate the modification of the high-frequency quantum modes, which is manifested by the reduction of the electronic coupling by nuclear Franck-Condon factors and by the change of the energy gap. Explicit expressions for the ET rates were obtained in terms of a sum over parallel vibronic channels, each involving a distinct intramolecular vibrational excitation of the final state. In the solvent-controlled adiabatic limit, the effects of intramolecular vibrational excitation are exhibited by the modification of the (partial) activation energies, while the frequency factor is dominated by the longitudinal dielectric relaxation rate of the solvent.