DOUBLE-ELECTRON EXCITATION OF H- BY FAST PROTON AND ANTIPROTON IMPACT

A theoretical investigation is carried out for double-electron excitat ion processes of H- induced by proton and antiproton impact at the ene rgy of 1.5 MeV. Excitation cross sections to the 2s2 S-1(e), 2s2p P-1( o), and 2p2 1D(e) states are calculated by using the plane-wave Born a pproximation, the distorted-wave Born approximation, and the close-cou pling method. Wave functions of H- are generated employing the hypersp herical coordinate method. It is shown that the low-lying continuum 1 skp P-1(o) is identified as an important intermediate state in the dou ble-electron excitation process to the 2p2 1D(e) state. We have also e valuated the ejected-electron spectra from the 2s2p P-1(o) shape-reson ance state. It is found that its spectral shape is close to the observ ed line profile of the photodetachment of H- since the excitation mech anism to this state is mostly dominated by the optically allowed trans ition at the projectile energy concerned here.