2026/04/27 by Abdelmalek Boumali · 1 voice
Physics and Astronomy · #physics.gen-ph
The single-ionization rate coefficient of a plasma neutral depends both on the microscopic electron-impact cross section and on the macroscopic shape of the electron energy distribution function (EEDF). We present a reproducible benchmark and sensitivity study -- not a new theory -- of these two effects for the three lightest neutrals He, Li, and Be, combining the recommended Bell~et~al. (1983) cross sections with a properly normalized two-temperature Tsallis q-generalized EEDF and varying q on both sides of the Maxwellian limit and the hot-electron fraction fhot at Thot=10 Tbulk. The calculation cleanly separates two independent uncertainty axes -- cross-section model (Bell vs. Lotz) and EEDF shape (Maxwellian vs. Tsallis). The Bell--Lotz spread on τM is small for He (within about 7%), moderate for Be (\lesssim 17%), and largest for Li (up to +95% at T=1~keV); sub-extensive distributions (q<1) suppress ionization through a hard tail cut-off, while super-extensive distributions (q>1) enhance low-temperature ionization through a κ-like power-law tail with κ=1/(q-1). The quantitatively safest non-Maxwellian cases are q=1 and q=1.2 (κ=5), which lie inside the finite-mean-energy regime; the cases q=1.4 and q=1.6 are retained as heavy-tail stress tests and should be read as qualitative trends rather than as quantitatively reliable predictions. Both EEDF effects scale with Ip/kBT, so He responds most strongly and Li least. The full numerical pipeline is released as a persistent reproducibility package, intended as a drop-in non-Maxwellian ionization module for collisional-radiative and ionization-balance modelling of light-neutral plasmas.