Quantum-classical rate coefficients for O2 + N2 inelastic collisions with very high vibrational levels

Authors: Yang, Jiawei; Hong, Qizhen; Bartolomei, Massimiliano; Pirani, Fernando; Coletti, Cecilia; Sun, Quanhua; Li, Jun

Journal: PHYSICAL REVIEW A

Publication date: 2025/03/06

DOI: 10.1103/PhysRevA.111.032804

Abstract: Energy exchanges among internal energy modes in O2 + N2 collisions directly affect the microscopic dynamical evolution of nonequilibrium phenomena in these gases. Quantum calculations of energy exchanges, especially those involving high molecular levels, are challenging due to their daunting computational costs. In this study, by capturing quantum effects associated with vibrational motions, we employ the improved mixed quantum-classical (MQC) method to obtain rate coefficients of both vibration-to-vibration (V-V) and vibrationto-translation or rotation (V-T-R) energy exchanges for O2 + N2 collisions over a wide temperature range (100-9000 K). This approach permits the achievement of results up to vibrational levels close to the molecular dissociation limit. The adopted potential-energy surface (PES) is formulated using a proper representation of both intermolecular and intramolecular components to provide the dependence of the interaction energy on molecular separation distances and molecular deformations. Notably, the MQC calculations with the new PES yield vibrational relaxation rate coefficients consistent with experimental data. In addition to the comprehensive MQC data, we utilize Gaussian process regression to predict rates for processes not directly computed, thus completing the V-V and V-T-R datasets for selected processes across full vibrational levels of O2 and N2. At low temperatures, notable anti-Arrhenius behavior is observed, which would enhance relaxation processes in cold environments typical of upper and planetary atmospheres. The extensive datasets are valuable for describing the kinetic behaviors of O2 and N2 across various vibrational levels and temperatures, aiding in addressing non-local thermodynamic equilibrium conditions where the influence of vibrationally excited air molecules cannot be ignored.