Atomic excitations in sputtering studied with group two element targets

Solid targets of Be, Mg, Zn, and Cd have been bombarded with 50 keV Ar+ ions. The relative excitation of the lowest-lying excited levels in sputtered neutrals and singly-charged ions have been measured using optical spectrometry. It is found that singly-charged ions are excited much more efficiently than neutral atoms. This is discussed, and it is concluded that atomic excitation in sputtering results from electron pick-up to excited states in initially ionized atoms rather than from inelastic atom-atom or electron-atom collisions. (Auth.)