Electron-impact excitation and ionization cross sections for ground state and excited helium atoms

Abstract

Comprehensive and critically assessed cross sections for the electron-impact excitation and ionization of ground state and excited helium atoms are presented. All states (atomic terms) with n ⩽ 4 are treated individually, while the states with n ⩾ 5 are considered degenerate. For the processes involving transitions to and from n ⩾ 5 levels, suitable cross section scaling relations are presented. For a large number of transitions, from both ground and excited states, convergent close coupling calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions, which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in graphical form.