Evidence for internal dielectronic excitation of slow highly charged uranium ions

We have measured x-ray emission from the neutralization of slow ${\mathrm{U}}^{\mathit{q}+}$ ions with charge states q=61–73 and energies of 7×q keV on a Be foil. We were able to resolve M-satellite groups and found an expected increase in M x-ray intensity with increasing number of M-shell vacancies in the incident ions. However, for charge states with no M-shell vacancies, we also observed a significant intensity of M x rays. We take this observation as evidence of an internal dielectronic excitation process occurring during the neutralization of the ions.