Vibrational nonequilibrium in a supersonic expansion with reaction: Application to O2–O

Abstract

The hypersonic expansion of O2 through a nozzle is considered. The steady nonequilibrium vibrational distribution function of O2, and the nonequilibrium forward reaction rate coefficient for the dissociation of O2 are calculated theoretically. In the first instance, the vibrational relaxation of O2 in the absence of reaction is examined in the temperature range 500–2500 K. The master equation for the vibrational populations, coupled to the steady one-dimensional conservation equations is solved numerically. The vibrational population obtained in this way, is compared to the distribution calculated using either a Treanor model or a Boltzmann distribution characterized by a vibrational temperature. The transition probabilities between O2 vibrational levels employed take into account the vibrational anharmonicity, and the anisotropic intermolecular potential. For the temperature range 2500–5000 K, the vibrational relaxation including dissociation and recombination is studied. The reactive probabilities that are required for this calculation were obtained from the model of Kiefer and Hajduk [Chem. Phys. 38, 329 (1979)].