Nonresonant multiphoton ionization of the neutrals ablated in laser microprobe mass spectrometry analysis of GaAs and Hg0.78Cd0.22Te

Abstract

A second, quadrupled Nd:YAG laser system has been incorporated into a laser microprobe mass spectrometer in order to ionize the neutral species contained in the vapor plume produced by the ablation laser of this microanalytical materials analysis technique. The irradiance of this focused postablation ionization (PAI) laser beam operating at 266 nm is sufficient to ionize all the neutral species having an ionization potential less than 9.3 eV that are contained within the irradiated volume via two photon nonresonant multiphoton ionization processes. This laser ablation/laser ionization configuration of the laser microprobe technique has been applied to the microanalysis of high-purity GaAs and Hg0.78Cd0.22Te target materials. The elemental ion yields produced in the PAI microanalysis of these materials are generally larger than those produced by the laser ablation only mode of laser microprobe analysis. The elemental ion yields of the constituents in these materials have also been evaluated as a function of the delay time between the firing of the ablation and PAI lasers at several ablation laser irradiances.