The dissociation of fast H2+ ions by hydrogen

Abstract

Abstract H2+ ions of energy 100 to 800 keV have been passed through hydrogen gas and the cross-sections for the following four processes determined : (1) H2+ → H+ + HO, (2) H2+ → H+ + H+, (3) H2+ → HO + HO, (4) H2+ → H2O. 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 H2O 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 13Ʃu 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.