Rate constant of the ion recombination in large ionic ensembles: a computer simulation study

摘要

Abstract: The rate constant of the diffusion-controlled recombination of ions in large ensembles of nonseparable ion pairs was calculated by means of computer simulation. The computer codes have been constructed to simulate diffusion-type transport and recombination of ions in model supersaturated solutions with different concentrations of ionic solutes and different dielectric constants of the solution. The simulations yielded the rate constant of the ion recombination as a function of the ion concentration. The calculated rates are compared with the theoretical Debye-Smoluchowski-type rate constant k$-DS$/ derived for isolated ion pairs and the Smoluchowski rate constant k$-s$/ for neutral reactants. It appears that the rate constant does not decrease with the increase of concentration, even in the range of 1 M solutions. The rate constants, for wide range of the dielectric permittivity, are slightly higher than the k$-DS$/ rate constant. A similar result has been obtained when the Jaffe model of the ion recombination in columns of ionization produced by a high energy particle was analyzed. The Jaffe kinetics agrees very well with the kinetics of recombination produced by the simulation codes only if the Jaffe rate k$-J$/ of ion recombination in multi-ion pair column, which is the free parameter of the Jaffe model, approaches the Debye- Smoluchowski rate constant k$-DS$/. !9