Electron-impact Ionization of Atomic Nitrogen

Abstract

New electron-impact ionization (EII) data are presented for neutral atomic nitrogen. The atom is treated as a 67-state system, incorporating Rydberg values up to n 20. State-specific cross sections for the first three states are from published B-spline R-matrix-with-pseudostates results. Binary-encounter Bethe calculations have been performed for the remaining 64 states. These data are designed for modeling the hypersonic chemistry that occurs when a space vehicle enters Earth's atmosphere from beyond orbit. The cross sections have been convolved into state-specific thermal rate coefficients and fit with the commonly used Arrhenius-Kooij formula for ease of use in shock-heated air plasma models. Additionally, rate coefficients are provided for a reduced 10-state system for use in coarse-grain models. For a given collisional-radiative model, these fine-and coarse-grain data can be used to generate state-specific rate coefficients for three-body electron-ion recombination, the time-reverse process of EII.

UQ eSpace

“…Initially, accompanying equations were also considered for electron impact ionisation from Drawin's method for excitation. This was discarded in the current model in favour of recent data presented by Ciccarino and Savin in [25]. This was as a result of the Drawin cross section approximations from [18] significantly overestimating the ionisation rate of high energy nitrogen states at high temperatures, and not accurately capturing the effects of lower energy states.…”

“…Ciccarino and Savin [25] present a comprehensive list of reaction rates for the ionisation of atomic nitrogen. This is done by collecting a selection of methods, including accurate R-matrix formulated cross sections for the first 20 energy states of atomic nitrogen.…”

“…All remaining transitions [25] Unlike atomic nitrogen, there were two models used for the ionisation of atomic oxygen. Similarly to the different models used for excitation, these are presented in an ordered tabled below.…”

“…Equation (32), or the modified Arrhenius Equation was chosen to fit forward rate coefficients (with fit constants A, n, and E), as it is used extensively in the field by all authors. Not only do many authors present their fitting parameters [10] [17] [25] for a function of this form, but Schmidt in [35] describes it as 'remarkably accurate'.…”