A numerical analysis of rate constants for dissociation of diatomic molecules under quasi-steady-state conditions of vibrational nonequilibrium

Description of a, nonequilibrium high-temperature flow of chemically reacti ng gas calls for model concepts of the rate constants for reactions taking place in the gas. No equilibrium in the chemical composition and between th e internal degrees of freedom (in particular, between vibrational excitatio n and translational (gas) temperature) served as a basis for development of numerous two-temperature models for dissociation rate constants. However, it has been known that the characteristic times of vibrational relaxation a nd dissociation of molecules behind the front of a strong shock wave are co mmensurate. Furthermore, a gain in the average vibrational energy per molec ule due to excitation of its vibrations behind the wave front becomes count erbalanced by a loss in this energy (average energy per molecule) through d issociation. Under these conditions, the average vibrational energy per mol ecule varies only slightly, and the gas behind the shock-wave front is said to be quasi-stationary in terms of vibrational energy. It is under these q uasi-steady-state conditions that a number of models of the rate constants for dissociation of diatomic molecules are analysed.