The influence of diffusion on the rate of a reversible quasi-unimolecular reaction in one, two or three dimensions

The role of diffusion in the kinetics of a reversible quasi-unimolecular reaction is considered. Equations that couple diffusion and reversible reaction are defined. From these equations are derived expressions for the concentrations of the reacting species, as a function of time, after a perturbation from their equilibrium concentrations. These expressions demonstrate how the time-dependent approach by a concentration to its equilibrium value is determined by the binding rate of adjacent molecules, the dissociation rate, the diffusion coefficients, the distance of closest approach of the reactants, the concentrations of the reactants, and the dimensionality. The expressions are applicable to perturbation-relaxation experiments in one, two, and three dimensions. The formalism is compared with previously existing theories.