Cold-target recoil-ion momentum spectroscopy studies of capture from atomic and molecular hydrogen by O⁸⁺ and Ar⁸⁺

We have used cold-target recoil-ion momentum spectroscopy to study electron capture from atomic and molecular hydrogen targets by slow (0.3<v<0.95 a.u.) O⁸⁺ and Ar⁸⁺ 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.