Identification and characterization of the dielectronic process in the formation of twoK-shell vacancies in atomic Li by fast electron impact

Abstract

Electron correlation effects in the production of two K-shell vacancies in lithium are investigated by bombarding atomic Li with 5-keV electrons. High-resolution Auger electron spectra show that discrete doubly vacant K-shell states are predominantly formed from ionization plus excitation, giving rise to the $2sns{}^{1,3}S$ and $2snp{}^{1,3}P$ states of ${\mathrm{Li}}^{+}.$ For these fast electron projectiles, the shake-up and dielectronic manifestations of the electron-electron interaction are shown to be the only mechanisms for creating the observed hollow states. The formation of the $2snp{}^{1,3}P$ states is found to be mediated only by the dielectronic process, permitting this aspect of the electron-electron interaction to be separately identified and its contribution characterized.