Non-equilibrium kinetics of the ground and excited states in N₂–O₂ under nanosecond discharge conditions: extended scheme and comparison with available experimental observations

A numerical 0D kinetic model is developed here to simulate the detailed kinetics of the ground and excited electronic states of atmospheric gases occurring under streamer discharge conditions. The model is based on an extended kinetic scheme that involves state-to-state vibrational kinetics of the ground electronic states of N₂, O₂ and NO diatomics, including e–V, V–V and V–T energy transfers, and contains about 10⁴ processes for more than 500 tracked state-specific states (including the higher excited and autoionising states of N^I/O^I atomic species), and also for state-non-specific species. This scheme takes into account the most important radiative processes occurring in N₂ and N₂–O₂ mixtures that are of diagnostic interest, including the extreme ultraviolet and vacuum ultraviolet radiation produced by many excited and autoionising states of N^I/O^I. The dependence of the rates of electron-impact processes on the reduced electric field E/N is found by solving the Boltzmann equation for electrons in the two-term approximation using the Boltzmann equation solver Open Source library, BOLOS.

We examine several test cases: pure nitrogen at 50 and 200 Torr and synthetic air at 10, 50 and 760 Torr, at a gas temperature of 300 K. The numerical results for pure nitrogen were compared with experimental results recently obtained by laser induced fluorescence for metastables. Good qualitative agreement was observed between numerical simulations and experiments at vibronic levels v  =  2–5, giving important feedback on the appropriateness of the kinetic scheme. Numerical results were also used to find several general spectrometric signatures that might be helpful in the development of diagnostic procedures. (paper)