Detection of Sputtered Neutrals by Multiphoton Resonance Ionization

Recently, we have demonstrated the selective ionization of atoms sputtered from solids by Multiphoton Resonance Ionization (MPRI) [1,2]. Three salient features of MPRI coupled to ion beam methods make it attractive as an analytical tool. First, the technique can be applied to all elements but He and Ne. Next, MPRI can be made selective to a single element by appropriate choice of the excitation wavelength, eliminating the need for a high resolution mass spectrometer. Both ground and excited state atoms can be examined. Finally, MPRI is extremely sensitive, i.e., with adequate photon fluxes every atom in the laser beam can be ionized [3]. As a consequence of this high sensitivity, the flux of ejected neutral species can be monitored under low dose bombardment conditions. Thus, MPRI of sputtered neutrals should be applicable to problems of structural and chemical analysis, as well as trace level determinations.