A new kinetic thermal nonequilibrium model for air plasma, considering vibrations of , and molecules in both the ground and electronically excited states in a state-to-state approach, was developed. The model treats in a consistent way the coupling of vibrational–electronic excitation of molecules and plasma chemical reactions as well as thermal nonequilibrium between translational degrees of freedom of electrons and heavy particles. The model was validated against the values of the radiation intensity of the and bands measured in the shock-tube experiments in an – mixture at shock wave speeds up to . Numerical analysis of thermally nonequilibrium processes in shock wave air plasma using the developed state-to-state model was conducted. It was shown that behind the shock front, a non-Boltzmann distribution over vibrational levels of , and molecules in both the ground and electronically excited states forms, but at the same time low vibration levels of these molecules are still populated in line with the local Boltzmann distribution with its own vibrational temperature. However, at extremely high shock wave velocities ( ) disruption of the Boltzmann distribution of and molecules starts from vibrational levels with quantum numbers , so it is worth using the state-to-state consideration in such cases.

The rate constants of elementary processes in the atom–diatom system $\mathrm{O}{(}^{3}P)+{\mathrm{H}}_2\left(v\right)$, including the processes of vibrational relaxation and dissociation, were studied using the quasiclassical trajectory method. All calculations were carried out along the ground potential energy surface (PES) ³$A^{″}$ that was approximated by a neural network. Approximation data were obtained using ab initio quantum chemistry methods at the extended multi-configuration quasi-degenerate second-order perturbation theory XMCQDPT2 in a basis set limit. The calculated cross-sections of the reaction channels are in good agreement with the literature data. A complete set of state-to-state rate constants was obtained for the metathesis reaction, the dissociation and relaxation of the H₂ molecule upon collision with an O atom. According to these data, Arrhenius approximations over a wide temperature range were obtained for the thermal rate constants of considered processes. Data obtained on the dissociation constants and VT relaxation of vibrationally excited H₂ molecules can be used in constructing kinetic models describing the oxidation of hydrogen at high temperatures or highly nonequilibrium conditions.

A thermal nonequilibrium kinetic model for a syngas/air mixture taking into account the state-to-state (STS) vibrational kinetics of CO, N₂, O₂, H₂, and OH molecules is developed. The physical and chemical processes occurring in the mixture when CO molecules are highly vibrationally excited by the absorption of the resonant CO laser radiation are considered. It is shown that the nonequilibrium vibrational excitation of a CO molecule leads to the acceleration of chemical reactions and makes it possible to initiate effectively the combustion of a syngas/air mixture. Due to the radiation absorption and vibrational-chemistry coupling, strongly non-Boltzmann vibrational distributions of the molecules are formed, which significantly influence the syngas combustion kinetics. The results of the STS model are compared with the predictions of simplified models that do not take into account vibrational nonequilibrium or the disruption of local Boltzmann vibrational distributions.

The rate constants of elementary processes in the atom-diatom system O(³P)+H₂(v), including the processes of vibrational relaxation and dissociation, were studied using the quasi-classical trajectory method. All calculations were carried out along the ground potential energy surface (PES) ³A′′ that was approximated by a neural network. Approximation data were obtained using ab initio quantum chemistry methods at the extended multi-configuration quasi-degenerate second-order perturbation theory XMCQDPT2 in a basis set limit. The calculated cross sections of the reaction channels are in good agreement with the literature data. A complete set of state-to-state rate constants was obtained for the metathesis reaction, the dissociation and VT relaxation of the H₂ molecule upon collision with an O atom. According to this data Arrhenius approximations over a wide temperature range were obtained for the thermal rate constants of considered processes. Data obtained on the dissociation constants and VT relaxation of vibrationally excited H₂ molecules can be used in constructing kinetic models describing the oxidation of hydrogen at high temperatures or highly nonequilibrium conditions.