OPTICAL-POTENTIAL STUDY OF ELECTRON-IMPACT EXCITATION OF HE+

Excitation of He+ by electron impact is studied in the energy range 4.4-14.71 Ry using a six-state close-coupling expansion together with an optical potential representing higher bound and continuum states. An 18-state basis set emphasizing long-range pseudostates is used for calculations below 100 eV, and a 17-state basis containing more compact pseudostates is used at higher energies. Total excitation cross sections for transitions from the 1s, 2s, and 2p states are also calculated using the optical theorem. A detailed comparison is made with a recent 15-state close-coupling calculation and with experiment, where possible. In general, inclusion of the optical potential significantly reduces the excitation cross sections.