Electron transfer, target excitation, and ionization in H++Na(3s) and H++Na(3p) collisions in the coupled-Sturmian-pseudostate approach.

Abstract

Total cross sections for electron transfer, target excitation, and ionization processes are reported for the ${\mathrm{H}}^{+}$+Na(3s) and ${\mathrm{H}}^{+}$+Na(3p) systems at 1--100 keV impact energies. We have employed a two-center coupled-Sturmian-pseudostate approach that has recently been developed and applied to several quasi-one-electron systems by Winter [Phys. Rev. A 48, 3706 (1993)]. The Sturmian basis set, together with an analytic Hartree-Fock potential, are chosen carefully so that all three channels (transfer, excitation, and ionization) are represented properly. We also discuss briefly the effects of the binding-energy correction on the calculated cross sections. We find that our various cross sections (${\mathrm{\ensuremath{\sigma}}}_{\mathrm{cap}}^{\mathrm{tot}}$, ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{cap}}^{\mathrm{H}(\mathrm{n}=2)}$, ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{cap}}^{\mathrm{H}(2\mathit{s})}$, ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{cap}}^{\mathrm{H}(2\mathit{p})}$, ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{exc}}^{\mathrm{N}\mathrm{a}(3\mathit{s}\ensuremath{\rightarrow}3\mathit{p})}$, ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{exc}}^{\mathrm{N}\mathrm{a}(3\mathit{s}\ensuremath{\rightarrow}3\mathit{d})}$, ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{ion}}^{\mathrm{tot}}$) and the ${\mathit{A}}_{20}$ alignment parameter for Na(3s\ensuremath{\rightarrow}3p) compare very well with most of the available experimental data, as well as with previous theoretical results.For all the above quantities, when a comparison is made between theory and measurement, our results are equally good or better than the earlier calculations employing different theoretical approaches. We still find a persistent discrepancy between theory (present as well as previous calculations) and measurements for the electron transfer cross sections into the metastable state of the H atom (${\mathrm{\ensuremath{\sigma}}}_{\mathrm{cap}}^{\mathrm{H}(2\mathit{s})}$). Our results for the orientation and alignment effects in the electron transfer process of ${\mathrm{H}}^{+}$+Na(3p) collisions are in good qualitative accord with recent observations and previous theoretical studies. In particular, we see a strong enhancement for the H(n\ensuremath{\ge}3) capture cross sections in the ${\mathrm{H}}^{+}$+Na(3p) collisions. The H(n=2) production cross sections in the ${\mathrm{H}}^{+}$+Na(3p) collisons follow a roughly similar trend, as observed experimentally when plotted against the impact energy.