Deuterium-Isotope Effect in the Chlorine Exchange between Hydrogen Chloride and Chlorine Atoms. A Study of Models for the Tunnel Effect

Abstract

The rates of the exchange reactions of chlorine atoms with hydrogen chloride and with deuterium chloride were measured as a function of temperature. Chlorine atoms were produced by photodecomposition of chlorine gas and their relative concentration was monitored by their reaction with deuterium: $$\mathrm{Cl}+{\mathrm{D}}_2\to \mathrm{DCl}+\mathrm{D}.$$ The temperature dependence of the logarithm of the ratio of rates was found to be nonlinear in the temperature range of 30° to 150°C. Various attempts to calculate the isotope effect assuming different types of tunneling are discussed.