Observation of internal dielectronic excitation with slow highly charged lead ions hitting surfaces

We investigated X-ray emission from highly charged slow Pbq+ ions (q = 50-5 8, E = 8.5 qkeV) hitting metal surfaces. We confirmed occurrence of interna l dielectronic excitation (IDE) i.e. excitation of the closed M-shell core by relaxation of "hollow-atom" electrons with a probability of unity. Calcu lation of singly and doubly excited states showed that population of singly excited states of n > 9 are most likely causing the core excitation. Furth er, we demonstrate a method for measuring the mean depth where X-ray emissi on occurs. The emission of the X-rays from ions with initial M vacancies oc curs inside the bulk.