Electron impact ionization of

The electron impact ionization cross section of is calculated using a distorted-wave approximation. The calculated cross section is compared to the experimental results of Peart and Dolder. The simplicity of the system allows an assessment of the accuracy of the distorted-wave approximation without complications from inaccuracies in the target state, initial continuum state, or final continuum states. The agreement with experiment is poor at low energies but improves substantially at higher energies. A differential cross section at an incident electron energy of 103 eV is presented. The proton energy distribution after the ionization is presented for large incident electron energy.