Electron-impact double ionization of Li+

Electron-impact direct double ionization (DDI) of the ground-state Li+ ion is investigated using an approach which takes into account contribution from ionization-ionization, ionization-excitation-ionization, and excitation-ionization-ionization processes. Reasonable agreement with the experimental data is obtained when bound electrons of the Li+ ion are considered as residing on the opposite sides of the nucleus. It is shown that distribution of the excess energy between the scattered and the ejected electrons, which participate in the next step of ionization, has a significant effect on the DDI cross sections. Better agreement with the experiment is obtained when electrons share the excess energy. The DDI study reveals the dominant role of the ionization-ionization process for the Li+ ion.