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The thermochemical nonequilibrium of the three lowest lying electronic states of molecular oxygen, O2(X 3 Σ − g , a 1 ∆g, b 1 Σ + g), through interactions with argon is studied in the present work. The multi-body potential energy surfaces of O2+Ar are evaluated from the semiclassical RKR potential of O2 in each electronic state. The rovibrational states and energies of each electronic state are calculated by the quantum mechanical method based on the present inter-nuclear potential of O2. Then, the complete sets of the rovibrational stateto-state transition rates of O2+Ar are calculated by the quasi-classical trajectory method including the quasi-bound states. The system of master equations constructed by the present state-to-state transition rates are solved to analyze the thermochemical nonequilibrium of O2+Ar in various heat bath conditions. From these studies, it is concluded that the vibrational relaxation and coupled chemical reactions of each electronic state needs to be treated as a separate nonequilibrium process, and rotational nonequilibrium needs to be considered at translational temperatures above 10,000 K.

State-resolved analyses of N + N2 are performed using the direct simulation Monte Carlo (DSMC) method. In describing the elastic collisions by a state-resolved method, a state-specific total cross section is proposed. The state-resolved method is constructed from the state-specific total cross section and the rovibrational state-to-state transition cross sections for bound-bound and bound-free transitions taken from a NASA database. This approach makes it possible to analyze the rotational-to-translational, vibrational-to-translational, and rotational-to-vibrational energy transfers and the chemical reactions without relying on macroscopic properties and phenomenological models. In nonequilibrium heat bath calculations, the results of present state-resolved DSMC calculations are validated with those of the master equation calculations and the existing shock-tube experimental data for bound-bound and bound-free transitions. In various equilibrium and nonequilibrium heat bath conditions and 2D cylindrical flows, the DSMC calculations by the state-resolved method are compared with those obtained with previous phenomenological DSMC models. In these previous DSMC models, the variable soft sphere, phenomenological Larsen-Borgnakke, quantum kinetic, and total collision energy models are considered. From these studies, it is concluded that the state-resolved method can accurately describe the rotational-to-translational, vibrational-to-translational, and rotational-to-vibrational transfers and quasi-steady state of rotational and vibrational energies in nonequilibrium chemical reactions by state-to-state kinetics.

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