Semiclassical Multi-State Dynamics of High-Energy O + O(2) Collisions: Influence of Electronic Excitation on Energy Relaxation.

Electronic excitation is particularly significant in high-energy or high-radiation environments. In this study, we use mixed quantum-classical dynamics calculations to simulate O + O electronically nonadiabatic collision dynamics involving multiple electronic states. We calculate rate constants for electronic-vibrational energy transfer in collisions with ' symmetry, and we use them to calculate the effect of electronically nonadiabatic transitions on energy relaxation. We find that although electronic excitation quantitatively reduces the rate constants for vibrational energy transfer, the dependence of the electronic-vibrational energy transfer on the collision energy can be accounted for by an extension of the activation-saturation (AS) model previously proposed (Zhao, X. 2024, 161, 231101) for electronically adiabatic atom-diatom collisional energy transfer. Multi-electronic-state master equation calculations with electronic-vibrational energy transfer rate constants described by the vibronic AS (VAS) model show that for the high-temperature nonequilibrium energy relaxation process of O + O, the electronically nonadiabatic effect increases the energy relaxation time by about 20%. By including electronically nonadiabatic transitions in the master equation, this research sheds light on the microscopic mechanisms of electron-vibration coupled energy transfer in high-temperature nonequilibrium flows, thereby providing guidance for energy relaxation prediction.