VIBRATIONAL-RELAXATION AND DISSOCIATION BEHIND SHOCK-WAVES .1. KINETIC RATE MODELS

This paper addresses the validation of the analytical nonperturbative semiclassical vibration-translation and vibration-vibration-translatio n rate models for the atom-diatom and diatom-diatom vibrational energy transfer molecular collisions. These forced harmonic oscillator rate models are corrected and validated by comparison with three-dimensiona l semiclassical trajectory calculations for nitrogen, which are widely considered to be the most reliable theoretical data available. A rema rkably good agreement is shown between the two models, for both the te mperature and quantum number dependence of single quantum and double q uantum vibration-vibration-translation Jumps in the temperature range 200 less than or equal to T less than or equal to 8000 K and for vibra tional quantum numbers 0 less than or equal to v less than or equal to 40. The simplicity of the theory, as well as the agreement shown, mak e the forced harmonic oscillator rate model attractive for master equa tion and direct simulation Monte Carlo modeling of nonequilibrium gas flows at very high temperatures, when the first order, vibration-vibra tion-translation rate models are not applicable, and where use of the three-dimensional trajectory calculations is very cumbersome and time consuming. The forced harmonic oscillator model is also applied to obt ain the probability of collision-induced dissociation of diatomics.