Production of hollow atoms by the excitation of highly charged ions in interaction with a metallic surface

The capture of many electrons by ${\mathrm{Ar}}^{17+}$ ions, at low velocity, near a metallic surface, has been studied. Multiexcited bound states with many electrons in the outermost shells (hollow atoms) have been observed. The surrounding of an ionic excited core by many outermost electrons greatly decreases the lifetimes of the states. This characteristic decrease explains the main striking features of the relaxation of the ions.