AB-INITIO ELECTRON-EMISSION CROSS-SECTION OF DOUBLY-EXCITED HE GENERATED BY FAST PROTON AND ANTIPROTON IMPACT

We report the first ab initio calculations of the electron emission spectra resulting from doubly excited (2s)2 1S(e), 2s2p 1P(o) and (2p)2 1D(e) states of He induced by 1.5 MeV proton and anti-proton impact. The He wavefunctions are generated by the hyperspherical close-coupling method, and the close-coupling equation for the whole collision system is solved in the semiclassical impact-parameter picture. Our result for both the background and the resonance profiles agrees excellently with the experimental data. The line profile by proton impact exhibits a significant difference from that by anti-proton impact.