Charge multiplication via Auger decay of L vacancies in the production of highly charged Ar ions by collisions with 1-MeV/amu Oq+ and Fq+

Abstract

Cross sections for the production of Ar recoil ions in collisions with 1-MeV/amu ${\mathrm{O}}^{\mathrm{q}+}$ and ${\mathrm{F}}^{\mathrm{q}+}$ (q=2 to bare nuclei) were measured by the time-of-flight technique. The cross sections for the production, by pure ionization, of recoil ions having charges greater than 6 display an unexpected behavior as a function of q. They rise at low q, reach a maximum in the vicinity of q=5--7, and then decrease at high q. Cross sections calculated using the independent-electron approximation rise continuously in this region and are lower than the experimental cross sections by as much as 4 orders of magnitude for high recoilion charge and low q. The observed turnover in the cross sections, as well as the large discrepancies in absolute magnitude between experiment and calculation, are accounted for by vacancy multiplication resulting from L-shell ionization followed by Auger decay.