The autoionisation contribution to the electron impact ionisation cross sections of C⁺and N²⁺at low energies

The contribution to the electron impact ionisation cross section of C + and N 2+ ions from autoionisation at incident electron energies below twice the ionisation energy is calculated by a method involving extrapolation of inner-shell ionisation cross sections. The magnitude of the effect is found to be in satisfactory agreement with that obtained by other methods. Results are compared with experimental data of Aitken et al. (1971) and discussed.