Double-K-shell vacancy production in Li-like C3+ ions colliding with helium

The formation of doubly-vacant, i.e., "hollow", states in 0.5-2.0 MeV/u Li- like C3+ ions colliding with helium has been investigated using high-resolu tion Auger electron spectroscopy From the measured spectra, hollow two-elec tron states corresponding to 2l2l' configurations can be identified, as wel l as hollow three-electron states corresponding to 2l2l'2l'' configurations . The results suggest that the electron-electron interaction is important i n producing the observed double-K-shell-vacancy states.