Electronic excitation of Ti atoms sputtered by energetic Ar + and He + from clean and monolayer oxygen covered surfaces

Abstract

Electronic excitation of Ti atoms ejected during energetic ion bombardment (Ar +, He +) of well characterized clean and oxygen covered polycrystalline Ti metal surfaces has been determined. For states with 0 to 2 eV and 3 to 5.5 eV of electronic energy, static mode laser fluorescence spectroscopy (LFS) and static mode spontaneous fluorescence spectroscopy (SFS) were used respectively. These experiments which were carried out in a UHV (<10 −10 Torr) system equipped with an Auger spectrometer provide measurements of the correlation between oxygen coverage (0 to 3 monolayers) and the excited state distribution of sputtered Ti atoms. The experimentally determined electronic partition function of Ti atoms does not show an exponential dependence on energy ( E) above the ground state but rather an E −2 or E −3 power law dependence.