Total and differential cross-section calculations for proton-impact ionization of hydrogen at low energies

We have computed the single-differential and total ionization cross sections for the proton-hydrogen collision system at low-energy range (0.1-10 keV/amu), using the electron translation factor corrected close-coupling method. Full convergence of ionization cross sections as a function of H-2(+) molecular basis size was achieved by including up to ten bound states and 11 continuum partial waves. The present results are compared with the available experimental data and various theoretical models. Our calculated cross sections are in an excellent agreement with the recent experiments of Shah et al. [J. Phys. B. 31, L757 (1998)], but decrease more rapidly than the cross sections measured by Pieksma et al. [Phys. Rev. Lett. 73, 46 (1994)] with decreasing energy. We have found that the 1ssigma(g) electron ionization is a rather higher-level ladder climbing process than a direct mechanism; the 2psigma(u) electron, on the contrary, is ionized directly and the higher levels act as a temporary trap.