Resonance Ionization Mass Spectrometry Using Ion-Beam Sampling

Abstract

Sputter atomization/resonance ionization mass spectrometry (SA/RIMS) is a highly sensitive technique for materials analysis which combines ion beam sputtering, resonance ionization, and mass spectrometry. A pulsed beam of high-energy primary ions bombards the sample producing a plume of neutral atoms. The cloud of sputtered neutrals is intersected and ionized by a synchronized, pulsed laser beam tuned to a resonant transition for specific sample atoms. Laser-generated ions are then extracted into a mass spectrometer for mass analysis. Ion beam sputtering allows the sampling process to be highly controlled by varying the energy, current density, and composition of the primary beam; the pulsed nature of the beam results in efficient sample utilization. Use of a micro-focused beam permits imaging of small areas and particles. The pulsed dye laser generates the high optical power necessary to efficiently ionize the sputtered atoms. Mass analysis of the laser-generated ions provides the capability for isotope ratio measurements.