Lyman line ratios in charge-exchange collisions of C6+ and O8+ ions with hydrogen and krypton atoms

Charge-exchange collisions of C6+ and O8+ ions with hydrogen and krypton atoms followed by radiative emissions are examined using the two-center basis generatormethod in the low-and intermediate-energy regimes. Capture cross sections are obtained within the independent-electron model and are used in a radiative cascade model to yield Lyman line-emission counts. The main focus of this analysis is on single-electron capture with the inclusion of autoionizing double capture in krypton collisions. Because hydrogen and krypton have the same first ionization potential, it is expected from the classical overbarrier model that the capture selectivity of these two atoms is the same, making krypton a good surrogate for hydrogen to study collision-induced radiative emissions in the laboratory. However, the present analysis shows that the subshell distributions with respect to the impact energy in krypton collisions can differ from hydrogen collisions and, hence, from predictions of the classical overbarrier model. Based on the comparison of present results with previous measurements, this difference in capture behavior of the two target atoms does not appear problematic for the Lyman line-emission results for C6+ collisions, but does appear to affect these results for O8+ collisions.