Study of H2++He → HeH++H at low energies

Laboratory-energy distributions of HeH+ were measured for the reaction H2++He → HeH++H (endothermic by 0.81 eV for ground-state reactants and products) with a merging-beams apparatus over a range of interaction energy W from 0.05 to 12 eV. The He was in the ground state; the H2+ was vibrationally excited. Absolute and relative cross sections were determined from these distributions. For W ≥ 5 eV, the distributions show that in the center-of-mass system the HeH+ peaks along both the incident direction of the H2+ and the incident direction of the He. The peak along the direction of the He is largest, and is the only one for W <5 eV. The role played by W and by the vibrational excitation of H2+ in the formation of the peaks is discussed. It is not clear what mechanism controls the reaction. The data cannot be satisfactorily explained with either the spectator-stripping or the Langevin model.