Charge transfer in slow collisions of O⁸⁺ and Ar⁸⁺ ions with H(1s) below 2 keV∕amu

We calculated the charge-transfer cross sections for O⁸⁺+H collisions for energies from 1 eV∕amu to 2 keV∕amu, using the recently developed hyperspherical close-coupling method. In particular, the discrepancy for electron capture to the n=6 states of O⁷⁺ from the previous theoretical calculations is further analyzed. Our results indicate that at low energies (below 100 eV∕amu) electron capture to the n=6 manifold of O⁷⁺ becomes dominant. The present results are used to resolve the long-standing discrepancies from the different elaborate semiclassical calculations near 100 eV∕amu. We have also performed the semiclassical atomic orbital close-coupling calculations with straight-line trajectories. We found the semiclassical calculations agree with the quantal approach at energy above 100 eV∕amu, where the collision occurs at large impact parameters. Calculations for Ar⁸⁺+H collisions in the same energy range have also been carried out to analyze the effect of the ionic core on the subshell cross sections. By using diabatic molecular basis functions, we show that converged results can be obtained with small numbers of channels.