STABILIZED DOUBLE-ELECTRON CAPTURE IN KRQ+ (Q = 17,18)-KR COLLISIONS

We have determined the distribution of n states initially populated in a double- or multielectron-capture collision of Kr(q+) (q = 17,18) with Kr at low energy (almost-equal-to 5 keV/u). Radiative decay curves of Rydberg transitions of the projectile ions were obtained by translating the target gas jet along the projectile beam. As a result for Kr18+ projectiles, we found that an initial population of Kr16+ equally distributed from n = 14 to 19 allows the observed Kr XVII 13-14 radiative decay curve to be reproduced relatively well. Furthermore, coincidence time-of-flight spectroscopy of photons emitted by recoil ions of given charge states was used to measure the radiative decay of recoil-ion transitions. From the Kr VII 7i-8k decay curve we deduced an initial population distribution of the Kr6+ recoil ion centered around n=20. These results lead to a better understanding of the mechanisms of double-electron capture responsible for populating Rydberg states, especially those in asymmetric configurations.