Inelastic collisions in theHe++H2system at low-keV energies

Abstract

The direct and charge-exchange scattering is studied in the ${\mathrm{He}}^{+}$ + ${\mathrm{H}}_2$ collision system. Charge exchange, which is investigated at energies from 0.5 to 3.0 keV and at angles out to 12°, rapidly becomes the most important collision process as the scattering angle increases. At least two dominant channels contribute to the charge exchange. Direct scattering is studied at 1.0, 2.0, and 3.0 keV and at small angles. The direct scattering shows ${\mathrm{He}}^{+}$ energy-loss spectra having four peaks representing elastic scattering and inelastic processes resulting from vibro-rotational excitation of the ground and electronically excited states of ${\mathrm{H}}_2$ and ${\mathrm{H}}_2^{+}$. It is shown that the collision involves the entire molecule and that there is negligible coupling between the electronic and vibro-rotational excitation. Reduced cross-section plots for the observed direct scattering exhibit a behavior suggesting that the inelastic processes result from interactions occurring at particular interparticle separations.