The effect of anharmonic intramolecular quantum modes on free energy relationships for electron transfer reactions

Numerical results of calculations of the probability of exothermic electron transfer between ions in a polar medium are presented. Account is taken of reorganization in both medium and intramolecular modes, where the latter are described by Morse potentials. In particular it is shown that negative intramolecular coordinate shifts give less curved free energy plots than harmonic potentials, and that the anharmonicity effects largely cancel each other when coordinate shifts of opposite signs in two intramolecular modes occur.