Calculations of electron-impact single-ionization cross sections of helium isoelectronic systems

The electron-impact single-ionization cross sections on the helium isoelectronic targets He, Li{sup +}, B{sup 3+}, C{sup 4+}, N{sup 5+}, O{sup 5+}, Ne{sup 8+}, Na{sup 9+}, Fe{sup 24+}, Ag{sup 45+}, and U{sup 90+}, are calculated using the recent simplified version of the binary-encounter dipole (siBED) model as applied by Huo [Phys. Rev. A 64, 042719 (2001)] to various molecular targets. The simple siBED model is good for the helium atom, but it is inadequate for ionic targets. Our proposed modifications: (i) ionic correction of the siBED model (QIBED) and (ii) relativistic corrections of the siBED model (RQIBED) are examined on a wider group of species and compared with other available experimental and theoretical results. The predictions of QIBED in the nonrelativistic energy domain and of RQIBED for all energies, with the same parameter values of siBED, produce excellent agreement with the experimental data and the results close to those of other theories for all the two-electron systems, neutral or ions on the same footing.