Comparison of variational Rice--Ramsperger--Kassel--Marcus theory with quantum scattering theory for the He+H+2 →HeH++H reaction

Three-dimensional quantum-scattering-theory calculations of the cumulative reaction probability (CRP) for the He+H+2→HeH++H reaction are reported for total angular momentum J=0. The results of these calculations are compared with variational calculations of the number of available states at the transition state for the dissociation of HeH+2 into HeH+ and H. For this reaction at zero total angular momentum two separate transition-state regions are found to exist throughout a broad energy range. The long-range transition state is found to be dominant for total energies up to at least 1.5 eV. As a result the energy spacings of the steps observed in the averaged CRP roughly correlate with the product rotational energy spacings