Master Equation Study and Nonequilibrium Chemical Reactions for H + H2 and He + H2

Complete sets of state-to-state cross sections and rate coefficients for the transition of 348 (v,j) rotational and vibrational states ofthe electronic ground state of the hydrogen molecule for H and He collisions were evaluated using quasi-classical trajectory calculations based on the latest potential energy surfaces. The state-to-state cross sections for the rotational and vibrational energy transitions were validated by comparing the results with those of quantum mechanical calculations and other quasi-classical trajectory calculations. The state-to-state rate coefficients were fed into a master equation, and the rotational and vibrational number densities were numerically evaluated. In this master equation study, relaxation of the rotational and vibrational temperatures, number density relaxation, and average rotational and vibrational energy losses due to dissociation were examined in heating and cooling environments. From the results of the state-to-state rate coefficients and the master equation study, dissociation and recombination rate coefficients were calculated under a quasi-steady-state assumption for a temperature range between 1000 and 32,000 K. These rate coefficients were validated by comparing the results with existing experiments. The reaction rates expressed by a two-temperature model based on translational and vibrational temperatures were also proposed upon collision with H and He, respectively.

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