On Cross Sections for Electron Impact Ionization of Multicharged Ions

Electron impact ionization cross sections calculated by means of two semi-empirical expressions (Lotz, Seaton), a semiclassical model (Burgess: "ECIP"), and a simple quantum approximation (Seaton) are compared with results of more elaborate quantum (Coulomb-Born) calculations and measurements for several multicharged ions (N2+, Mg2+, C3+, O3+, C5+, O5+, Fe14+). While in some cases the comparisons are not definitive, the simple formula of Lotz appears to represent the C-B and experimental results more consistently than the other methods.