The dissociative ionisation of hydrogen by 5-25 keV protons: energy spectra and angular distribution of fragment ions

The energy and angular distributions of fragment protons produced in H + -H 2 collisions have been investigated within the energy range 5-25 keV. The observed energetic protons arise from at least four repulsive states, the 2p sigma u , 2p pi u and 2s sigma g states of H 2 + and the unbound H + H + state. No significant contribution from autoionisation is observed. Analysis of the angular distributions has been performed to distinguish the separate degenerate channels available to the ejected electron. The results show a remarkable similarity to photoionisation data.