Charge exchange and excitation in H+He2+ and He++H+ collisions using single- and multichannel perturbed-stationary-state propagators.

Abstract

Our recently formulated (preceding paper, PP I) semiclassical perturbed-stationary-state single- and multichannel propagators are applied to study the collisions of ${\mathrm{He}}^{2+}$ on H(1s) and ${\mathrm{H}}^{+}$ on ${\mathrm{He}}^{+}$(1s), including as many as 45 molecular adiabatic states unmodified by an electron translation factor. In the energy range below the collisional ionization threshold, a multichannel eikonal propagator with 45 states reproduces the total charge-exchange cross sections---a feat that a single-channel theory cannot accomplish, as convergence with respect to the basis size indicates conclusively. In this region of negligible ionization, the 45-state multichannel cross sections are also in reasonably good agreement with other semiclassical calculations that employ either atomic or molecular basis functions modified by translation factors. Regarding level-selective cross sections, however, our results and previous translation-factor-based predictions are far apart. The multichannel propagator yields higher cross sections for transfer into excited states whose participation is artificially attenuated in the other models by the translation factor. In light of our findings, we discuss recent experimental measurements of uv emission induced in collisions of hydrogen and \ensuremath{\alpha} particles and suggest an interpretation that invokes optical interference to explain the observed Balmer-\ensuremath{\alpha} cross sections and, perhaps, also the slightly low radiative-quenching yield of the product metastable helium ion.