Drift and reactions of positive tetratomic ions in dry, atmospheric air: Their effects on the dynamics of primary and secondary streamers

The ion swarm data, namely, the reduced mobility, diffusion, and reaction rates of the positive tetratomic ions O 4 + and N 2 O 2 + in N 2 and O 2 have been determined from a Monte Carlo simulation using calculated and fitted elastic and inelastic cross sections. The elastic momentum transfer cross sections have been determined from a semiclassical Jeffreys-Wentzell-Kramers-Brilouin (JWKB) approximation based on a rigid core potential model well adapted for polyatomic ions. The inelastic cross sections have been approximated from considerations based on the N 4 + / O 2 and N 4 + / N 2 systems. The validated cross section sets in pure N 2 and O 2 have been used to determine the O 4 + and N 2 O 2 + swarm data in dry air over a large E/N range up to 1000 Td. However, due to the lack of experimental ion transport coefficients necessary for a more rigorous cross section validation, the present data, validated only at low E/N, should be regarded as a first approximation, susceptible to improvements as soon as measurements of ion transport coefficients become available in the literature. Then, the present data are used in a two-dimensional discharge dynamics fluid model for the simulation of the primary and secondary streamers for the case of a positive point-to-plane corona discharge in dry air. Relevant characteristics such as discharge current, charged particle densities, space charge electric field and the variation in active species like N and O radicals (very useful in many nonthermal plasma applications) are analyzed and discussed with and without the consideration of three positive tetratomic ions ( N 4 + , O 4 + , and N 2 O 2 + ). More particularly, the non-negligible effect of O 4 + , in the dynamics of the primary and secondary streamers during the discharge propagation and relaxation stages is highlighted with an emphasis on the role of the related kinetic reactions occurring between the different charged particles.