Molecular treatment of electron capture in atomic collisions in the meV- to keV-energy regime: Collisions of C5+ ions with H atoms and the effect of core electrons.

Abstract

Electron-capture processes in collisions of ${\mathrm{C}}^{5+}$ ions with H atoms are investigated theoretically by using quantum-mechanical and semiclassical molecular-orbital methods in the collision-energy range from meV/amu to keV/amu. Atomic-type electron-translation factors are appropriately incorporated to ensure correct scattering boundary conditions. Total capture cross sections have a broad minimum at 0.4 keV/amu that is caused by the change of major contributors. The dominant capture channels in the triplet manifold are ${\mathrm{C}}^{4+}$(1s4s) below 0.1 keV/amu and ${\mathrm{C}}^{4+}$(1s4p), ${\mathrm{C}}^{4+}$(1s4d), and ${\mathrm{C}}^{4+}$(1s3p) above that energy. In the singlet manifold, below 0.5 keV/amu, the dominant channel is ${\mathrm{C}}^{4+}$(1s4s), as in the triplet manifold. However, above that energy the ${\mathrm{C}}^{4+}$(1s4f), ${\mathrm{C}}^{4+}$(1s4d), ${\mathrm{C}}^{4+}$(1s3p), and ${\mathrm{C}}^{4+}$(1s3d) channels become important. The present results for the total capture cross section is in excellent accord with the measurements by Phaneuf et al. [Phys. Rev. A 26, 1892 (1982)] and Crandall, Phaneuf, and Meyer [Phys. Rev. A 19, 504 (1979)] over the entire energy region studied. The effect of core electrons on the capture process is examined by using data from the present (${\mathrm{C}}^{5+}$+H) system and the previously studied (${\mathrm{N}}^{5+}$+H) and (${\mathrm{B}}^{5+}$+H) systems, and some remarks on the role of core electrons are made on the basis of an argument concerning the overlap of electronic charge distribution.