The dissociation of fast H 2 + ions by hydrogen

H 2 + ions of energy 100 to 800 keV have been passed through hydrogen gas and the cross-sections for the following four processes determined : (1) H 2 + → H + + H O , (2) H 2 + → H + + H + , (3) H 2 + → H O + H O , (4) H 2 + → H 2 O . A magnetic field was used to separate the fast dissociation products of different e / m , and CsI(Tl) scintillation crystals were used as detectors. Double-height pulses resulted when two particles of the same e / m , simultaneously entered one of the crystals and were clearly resolved from single pulses. Processes (3) and (4) were separated by moving a fine slit across the neutral-particle counter which thus counted only H 2 O particles as double pulses. The partial cross-sections for processes (1) and (2) show an E -1 dependence at high energies. The energy dependence is less marked below 300 keV, where the Born approximation might be expected to be invalid. The partial cross-sections for processes (3) and (4) show the strong energy dependence characteristic of an electron-exchange process. The angular distribution for process (3) is consistent with the reaction proceeding via the 1 3 Ʃ u repulsive triplet state. The large fraction of the capture reactions proceeding this way (70%), is reasonable considering the high probability of formation in the triplet state. The large values of the cross-sections for processes other than simple dissociation account, in part, for the considerable discrepancies between the results of other workers.