A theoretical method for analytical calculation of nonequilibrium dissociation rates at high temperatures is developed. The model is based on the assumption of classical impulsive collisions. Dissociation is considered to occur mostly through an optimum configuration, that is, a set of collision parameters minimizing the energy barrier. This optimum configuration defines the threshold kinetic energy for the dissociation, and through it - the exponential factor of the rate coefficient. The probability of finding the colliding system near the optimum configuration determines the preexponential factor of the rate. The dissociation probabilities obtained obey a power law with respect to kinetic energy in excess of the threshold, the exponent in the power law with respect to kinetic energy in excess of the threshold, the exponent in the power law being determined by the number of degres of freedom of the colliding system. Singularities, or collision resonances, are shown to reduce the effective number of degrees of freedom near certain energies. The importance of rotational energy in nonequilibrium dissociation is demonstrated, including both "internal" vibration-rotation interaction in the dissociating molecule and rotational energy of its collision partner. simple analytical formulae for two- and three-temperature rate coefficients obtained can be used in hypersonic shock flow computations. Also presented are some results of master equation modeling of relaxation behind strong shocks. The modeling was performed using a new set of relaxation rates based upon a non-perturbative approach with account for multiquantum vibrational transitions which is very important at high temperatures.
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