Quasi-classical trajectory analysis of three-body collision induced recombination in neutral nitrogen and oxygen.

This article presents a theoretical and computational framework using the Quasi-Classical Trajectory (QCT) method to model three-body collisions and gas-phase recombination in dilute oxygen (O/O₂) and nitrogen (N/N₂) atom/diatom mixtures. A new formulation of the three-body collision rate constant is developed based on the lifetimes of binary collisions, with triple collisions initiated by sampling the arrival time of a third particle within these lifetimes. The study quantifies recombination probabilities, rate coefficients, and internal energy distributions of recombined products across different collision pathways, finding that long-lived binary collisions, although observed for atom-diatom pairs, are rare and do not significantly influence recombination rates near equilibrium conditions. The recombination rate coefficients computed without invoking the principle of detailed balance agree within an order of magnitude with those inferred from detailed balance, supporting the validity of existing models and suggesting the framework's potential utility for nonequilibrium conditions and future Direct Molecular Simulation applications.