Geminate recombination in proton-transfer reactions. II. Comparison of diffusional and kinetic schemes

The diffusional and kinetic approaches are compared for geminate dissociation-recombination reactions. When steady-state rate coefficients to and from a distance defined as a "complex cage" are evaluated from the diffusion equation, one obtains encouraging agreement between the transient analytic solution of the rate equations and the exact numerical solution for diffusion with backreaction over a finite time regime. However, the rate equations cannot accurately describe the decay of the dissociating molecule for very long times, since as we prove below, the asymptotic decay according to the diffusional scheme is t ^-3/2, while for the rate equations it is exponential. New experiments, over an extended time regime confirm these conclusions.