Electron impact ionization cross sections of molecules: Part II. Theoretical determination of total (counting) ionization cross sections of molecules: a new approach

Abstract

Cross sections for single ionization of molecules by electrons (threshold ⩽ E ⩽ 200 eV) have been calculated using a newly developed semiclassical formula. The formula is a combination of the classical binary encounter approximation, the Born-Bethe approximation and the additivity rule. This formula has been applied to H 2, N 2, O 2, H 2O, CO 2, C 2H 2, NH 3, CH 4, CF 4, C 2H 4, CH 3OH, SF 6, UF 6, C 2H 6 and C 6H 6 and the cross sections obtained have been compared with results from the classical binary encounter approximation (Gryzinski formula), the semiclassical Jain-Khare approach, and reliable experimental data. The main advantage of the present treatment is that ionization cross sections can be described by a simple analytical formula (depending only on basic atomic properties), which yields results in better agreement with experimental data than the classical formulae.