State-to-State Analysis of Recombination processes in non-equilibrium N₂₊N and O₂₊O chemical systems in a 0-D isothermal reactor

This work aims to study the energy transfer and recombination processes of N₂(Σ⁺_g)+N(⁴S_u) and O₂³ Σ⁺_g)+O(³P₂) chemical systems in a 0-D isothermal reactor. The gas mixture which consiStS primarily of atoms and a small percentage of molecules, initialized at a high internal temperature of 10000 K, is suddenly plunged into a heat bath at a lower temperature of upto 2500 K for nitrogen and 1500 K for oxygen thus inducing recombination. The internal energy state population distribution for each molecular system is determined for a wide range of simulation conditions by numerically solving a system of master equations. The internal, rotational and vibrational temperatures are extracted from the population distribution by computing average energy. The conventional assumption of faster equilibration of rotational mode as compared to the vibrational mode holds for N₂+N chemical system while it is not a very strong assumption for O₂₊O as the two relaxation times are comparable. A macroscopic recombination rate constant is calculated by solving the master equations to determine an effective rate constant for the quasi-steady state (QSS) period. The QSS assumption holds well for high-lying energy levels while the low-lying energy levels experience a change in relative population distribution as recombination progresses.