The ionization of Li⁺and Mg⁺by electron impact

Cross sections for the single ionization of Li + and Mg + by electron impact are calculated in the Coulomb-Born approximation (neglecting exchange), and compared with recent experimental results. In the case of Li + it is shown that the Bethe-Born approximation is not valid until the incident electron energy is much greater than previously supposed. For Mg + , it is shown that ionization from inner shells provides an important contribution to the cross section. Contributions from autoionization are also shown to be significant but do not introduce large irregularities in the total cross section.