Cold-target recoil-ion momentum spectroscopy studies of capture from atomic and molecular hydrogen byO8+andAr8+

Abstract

We have used cold-target recoil-ion momentum spectroscopy to study electron capture from atomic and molecular hydrogen targets by slow $(0.3<\mathrm{v}<0.95\phantom{\rule{0.3em}{0ex}}\text{a.u.})$ ${\mathrm{O}}^{8+}$ and ${\text{Ar}}^{8+}$ ions. For the atomic hydrogen target, we have performed coupled-channel calculations using an atomic orbital expansion to compare to the experimental results. The $Q$-value spectra show strong populations of both $n=5$ and $n=6$ states on the projectile, with a tendency for increasing the population of high-angular momentum states for higher projectile velocity. A strong population of $n=6$ is found, a result not previously reported but in good agreement with the present calculations.