Measurements of ion-molecule reactions of He+, H+, and HeH+ with H2 and D2

Abstract

A drift tube‐mass spectrometer apparatus has been used to determine the rate coefficient, energy dependence, and product ions of the reaction He+ + H2. The total rate coefficient at 300 K is (1.1±0.1)×10−13 cm3/sec. The reaction proceeds principally (80%) by dissociativecharge transfer to produce H+, with the small remainder going by charge transfer to produce H 2 + and by atom rearrangement to produce HeH+. The rate coefficient increases slowly with increasing ion mean energy, reaching a value of 2.8×10−13 cm3/sec at 0.18 eV. The corresponding reaction with deuterium, He+ + D2, exhibits a value (5±1)×10−14 cm3/sec at 300 K. The reaction rates for conversion of H+ and HeH+ to H 3 + on collisions with H2 molecules are found to agree well with results of previous investigations.