Rovibrational-Specific Kinetics Database and Master Equation Study for the O2 + N and NO+O Systems Using Ground Electronic State NO2 Potential Energy Surfaces

Abstract

Motivated by the study of high-enthalpy air flows, this work investigates the nonequilibrium kinetics of the O₂ + N and NO + O systems. Rovibrationally resolved kinetic data for the O₂ + N and NO + O systems are generated using quasi-classical trajectory (QCT) simulations performed on high-fidelity ab initio potential energy surfaces (PESs). State-specific cross sections and rate coefficients are computed over a wide range of collision energies and initial rovibrational states and subsequently incorporated into a master-equation framework to evaluate thermal and quasi-steady-state (QSS) rate coefficients, internal energy transfer, and dissociation energy removal. The results reveal strong mode-specific effects in dissociation kinetics. For both systems, dissociation rates increase sharply with internal energy; however, at fixed total energy, molecules with high vibrational energy dissociate several orders of magnitude faster than those with low vibrational energy but matched internal energy, demonstrating clear preferential vibrational promotion. Bound–bound transitions show that higher-multiplicity potential energy surfaces significantly enhance inelastic transition rates, particularly for large energy gaps. Master-equation analysis indicates that vibrational and rotational modes relax on distinct time scales at low temperatures, with convergence at higher temperatures driven by increased collisional efficiency. Comparison with data from literature reveals the importance of the inclusion of the sextet PES in accurately predicting the energy relaxation rates. These results provide detailed insight into energy transfer and dissociation dynamics in the NO₂ system and establish a physically consistent basis for reduced-order kinetic modeling under nonequilibrium conditions.