Electron impact excitation of hydrogenic ions in a modified Coulomb-Glauber approximation

The Coulomb-Glauber approximation is modified to overcome the inadequate semiclassical treatment of close encounter collisions. This modified approach is applied to 1s-2s and 1s-2p excitation of He+ by electron impact in the energy range 100-1000eV and is found to affect the cross section in the intermediate and large scattering-angle region. The integrated cross section however remains almost unchanged. The scaled cross sections Z4σ for the n = 2 excitation of hydrogenic ions are evaluated in the energy range 25Z2- 250Z2 eV and are compared with the results of earlier workers. (author)