How much does thermal nonequilibrium influence the overall atomic recombination during de-excitation?

A parametric study is carried out via state-to-state constant-volume heat bath simulations for binary mixtures of O₂/O and N₂/N to identify nonequilibrium de-excitation conditions where the overall atomic recombination is influenced by thermal nonequilibrium and where it is not. The most important parameter is found to be the translational temperature at which the de-excitation occurs. A low translational temperature of around 500 K is found to prevent the overall atomic recombination process from being influenced by the thermal nonequilibrium, due to the small value of K_EQ making the dissociation reaction less important. At a higher translational temperature of 2000 K, the overall atomic recombination process is influenced by the thermal nonequilibrium to an extent that is comparable to that seen in the corresponding excitation conditions, due to the nonequilibrium-accelerated dissociation rate. The current results have important implications in reduced-order modelling and experimental methods.