Modified method of perturbed stationary states. IV. Electron-capture cross sections for the reactionC6++H(1s)→C5+(n,l)+H+

Abstract

Previously reported ten-state perturbed stationary-state calculations for ${\mathrm{C}}^{6+}\ensuremath{-}\mathrm{H}(1s)$ collisions are extended by increasing the basis to include all molecular states correlating to the principal levels $n=3,4, \mathrm{and} 5$ of the final ${\mathrm{C}}^{5+}(\mathrm{nlm})$ atomic ion. This allows cross sections to be computed for the angular momentum sublevels, $l$, of each of the above $n$. The H-atom energy range extends from 13 eV to 27 keV. Adiabatic calculations are done for energies below 1.3 keV, and partially diabatic calculations are done at higher energies. The inclusion of states with magnetic quantum number $m\ensuremath{\ge}2$ in the new basis leads to significant increases in the $n=5$ capture cross section even at rather low energies. Two translational factors, which depend on the internuclear separation, are employed in the construction of the scattering basis. One is used for the state which correlates to $\mathrm{H}(1s)$; the other is used for all states correlating to states of ${\mathrm{C}}^{5+}$. For purposes of comparison, cross sections are also computed for the same scattering basis, with the use of the method of Bates and McCarroll and the method of Piacentini and Salin. The heavy-particle motion is treated semiclassically, with the use of Riley's average approximation at energies below 1.3 keV and the straight-line impact-parameter method at higher energies. As in the ten-state calculations, it is shown that adiabatic and diabatic formulations lead to rather different values for the cross sections at the higher energies. The results are compared with the experimental and theoretical cross sections obtained by other researchers.