Electron impact ionization of multicharged ions

Computations have been made of the electron-impact ionization cross sections of multicharged ions of C, O, N, Ne, and Ar in the binary-encounter approximation. For ions of the four lighter species, the dominant ionization mechanism is that of direct electron ejection to the continuum. For Ar, excitation of inner-shell electrons to unoccupied bound levels with subsequent autoionization can also make a significant contribution to the total ionization process for some ions. The calculated binary-encounter values are in reasonable agreement with recent experimental data and with the quantum-mechanical calculations of Trefftz for O⁺⁴ and O⁺⁵.