Study of atomic excitations in sputtering with the use of composite targets

Abstract

Some Li- and Na-compounds were bombarded with 80keV Ar + ions, and the excitation of sputtered particles was studied with optical spectrometry. Very strong excitation of Li I and Na I was observed, but essentially no excitation of electronegative elements. For levels in Li I and also in Na I with n ⩽ 8, the relative excitation probabilities decrease as power laws versus the effective quantum number of the excited term. However, in some cases, for Na I and with n > 8, the relative level populations fall noticeably above the extrapolation of such power law behaviors. This is discussed and tentatively interpreted in terms of two-step processes, (i) The projectile excites a target electron from the valence band to the conduction band. (ii) Such an excitation is transferred resonantly to the sputtered atom on its way out.