Theoretical study of ion-pair formation and Penning and associative ionization in low- to intermediate-energyHe*(21,3S)+Li collisions

A semiclassical treatment based on a molecular orbital expansion is used to study ion-pair formation and Penning- and associative-ionization processes in ${\mathrm{He}}^{\mathrm{*}}$(2 ${}_{}{}^{1,3}{}_{}{}^{}$S)+Li collisions in the energy regime from 100 to 1000 eV. Although these processes are usually important in different energy ranges, here they are found to compete with each other to an appreciable degree and hence to provide a rare opportunity for investigating collision dynamics that require an equal-footing treatment between autoionization to the continuum and a discrete transition. The present cross sections for these processes compare favorably with the measurement of Wang, Tang, and Neynaber [J. Phys. B 20, 1527 (1987)].