Ionization and Single and Double Electron Capture in Proton-Ar Collisions.

Total cross sections for formation of H and H, and electron production, in H + Ar collisions have been calculated at energies between 100 eV and 200 keV by employing two methods: for E < 10 keV, a semiclassical treatment with an expansion in a basis of electronic wave functions of the ArH quasimolecule and, for E > 10 keV, the switching-classical-trajectory-Monte Carlo method (s-CTMC). The semiclassical calculation involves transitions to molecular autoionizing states, calculated by applying a block-diagonalization technique. The s-CTMC method is adept to treat two-electron processes and yields total cross sections for H formation in reasonably good agreement with the experimental data. Cross sections for electron- and H-production processes, which are dominated by one-electron transitions, are in good agreement with the experimental data.