Differential excitation cross sections for electron impact onLi+: A study of continuum coupling effects

Differential excitation cross sections for the transitions from 1 ${}_{}{}^1{}_{}{}^{}\mathrm{S}$ to 2${\mathrm{}}^3$S, 2${\mathrm{}}^1$S, 2${\mathrm{}}^3$P, and 2${\mathrm{}}^1$P in He-like ${\mathrm{Li}}^{+}$ are calculated in the distorted-wave and close-coupling approximations in order to study their sensitivity to continuum coupling effects. Comparisons are made between nonunitarized distorted-wave, 5-state unitarized distorted-wave, 5-state close-coupling, and 11-state close-coupling calculations. The results indicate that the shape of the cross sections, as a function of scattering angle, can be significantly different for the various levels of approximation, even when the total cross sections are in reasonably close agreement.