Theory of Atomic Recombination on Surfaces

Abstract

A simple kinetic theory for atomic recombination on solid surfaces employing the Rideal mechanism is presented. The temperature dependence of the reaction rate is discussed in terms of ``transition temperature'' which characterizes change in the kinetic order of the recombination reaction with respect to the gas-phase atom concentration. The transition temperatures are shown to correspond to the maxima and the minima of the reaction rate. The experimental data of Wood and Wise and others for hydrogen recombination on glass surfaces are satisfactorily reproduced with the assumption of two types of adsorption sites on glass surfaces having the binding energies of 42 and 2.1 kcal/mole, respectively. Qualitative agreement is also found with the limited experimental data for hydrogen recombination on metals. A comparison of the present theory with the steady state theory of De Boer and Van Steenis is given in the Appendix with a refined definition of the partition function for the activated complex in the reaction on surface.