Predissociation of optically forbidden states in electron-hydrogen collisions as studied by coincident electron energy-loss spectroscopy

Abstract

The electron energy-loss spectra of in coincidence with H(2p) formation have been measured in the range just above the dissociation limit of H(1s) + H(2p) at the incident electron energies of 30 and 150 eV and the scattering angle of . The ordinary energy-loss spectra at the same incident energies and scattering angle have also been measured. It is clearly seen that optically-allowed states dominate in the ordinary energy-loss spectra while optically-forbidden states contribute noticeably to the coincident energy-loss spectrum at the 30 eV incident energy. The forbidden states predissociating into H(1s) + H(2p) are assigned and the branching ratio of the predissociation, the intensity ratio of the coincident energy-loss spectrum to the corresponding ordinary one, is obtained. The predissociation pathways into H(1s) + H(2p) from those forbidden states are discussed in detail.