First principles calculations of air fluorescence efficiencies with comparisons to measurements

The fluorescence efficiencies used in calculating the optical emissions produced by energetic particles and penetrating radiation in air are derived for the most part from the measurements, of Davidson and O'neil, Mitchell and Hartman. These efficiencies were obtained from experiments conducted at various air pressures and in the absence of an applied electric field. In this paper we describe detailed 4.5 dimensional (two spatial dimensions and 2.5 phase space dimensions) kinetic calculations for the electron distribution function resulting from the injection of energetic electrons into air at various pressures. We choose beam parameters and dimensions that are directly relevant to the original Davidson and O'Neil experiments. From the electron distribution function and measured excitation cross-sections we then compute the optical efficiencies for a large number of nitrogen and oxygen lines across the electromagnetic spectrum from 320.0 nm to 800.0 nm. A comparison with various measurements is presented. We also present results from simulations with an applied electric field. The computed fluorescence efficiencies can be used to determine the optical emissions associated with high-altitude discharges driven by runaway air breakdown and results are discussed in a separate poster. We have also recalculated optical emission rates that are applicable to discharges dominated by. conventional breakdown for comparison with Taranenko et al. These rates are also used in our self-consistent sprite simulations.