FREE-ENERGY GAP LAW UNDER DIFFUSION CONTROL

The free energy gap law in forward and back electron transfer (bimolec ular and geminate) is examined. Both processes are specified by positi on-dependent rates of remote electron transfer. These rates are used w ithin encounter theory to calculate the bimolecular rate constants of ionization and recombination as well as the quantum yield for photoche mical ion separation. The free energy gap law is shown to be a propert y of kinetic-controlled reactions. In the diffusion-controlled Limit t his law for either forward or backward reaction constants is violated at the top of Marcus' parabola. This conclusion pertains equally to an analogous quantity extracted from the separation quantum yield for ge minate recombination.