Dissociation and recombination of a diatomic molecule involving two states which only interact via the atomic species. I

The master equation which describes the relaxation of a diatomic molecule with two states, diluted in some background gas from a non-equilibrium to a final equilibrium population distribution at constant temperature is developed. The only path from one state to the other is assumed to be via the atomic species. An approximate solution is obtained using singular perturbation theory based on the assumption that the internal relaxation time in each state is much shorter than the time for dissociation from either state. This assumption leads to a master equation involving two small parameters, one for each state. The approximate solution is obtained by considering two cases involving these small parameters. The existence of rate constants and the validity of the Rate-Quotient Law is also discussed. (Auth.)