Rigorous Rate Constants for Diatomic Recombination and Dissociation in a Dilute Gas

We obtain rigorous formulas for the forward and backward rate constants for the reaction $A_2\leftrightarrows A+A$. Explicit evaluations are given near equilibrium. General asymptotic results for deep, as well as for shallow, binding potentials are derived. Experimental data for ${\mathrm{Br}}_2$ in Ar compare favorably with our theoretical results. We conclude that the attractive part of the catalytic potential is essential to obtain the negative value of the temperature coefficient that is demanded by experimental evidence.