OPTICAL-EMISSIONS FROM SPUTTERING SPECIES FORMED BY THE FAST ION-BOMBARDMENT OF CLEAN AND OXYGENATED MG SURFACES

Mg has been bombarded by 5 keV Kr+ ions and the sputtered neutrals and ions in excited states studied by their optical emissions. Spectra were obtained in ultrahigh vacuum or under oxygen partial pressure, as a function of the incidence angle of the incoming beam with respect to the target. For grazing incidence a doubling in the line shape of Mg II is interpreted in terms of a mirror effect and subsequently the kinetic energy of ejected particles is deduced from the Doppler doubling. We show that ionic species Mg II are ejected with kinetic energies one order of magnitude higher than neutral Mg I.