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Materials analysis using laser-based spectroscopic techniques

In this paper several laser-based spectroscopic methods capable of detecting low concentrations of a particular element are described, with particular emphasis on the contrasting techniques of Laser-Induced Breakdown Spectroscopy (LIBS), and Resonance Ionisation Mass Spectroscopy (RIMS). Simple mathematical treatments, based on thermodynamic considerations and rate equation models, are given for both systems, allowing semiquantitative analysis from the magnitudes of observed signals. Experimental results are presented for both methods. For LIBS these include the determination of the concentration of alloy constituents, the detection of surface contaminants and the use of measured line intensities to calculate electron temperatures in laser-produced plasmas. For RIMS, detection of the geologically important element rhenium (Re) was accomplished in the gas phase at a level of 4 x 10 8 atoms/cm3, and the relative proportions of the stable isotopes 185Re and 187Re were measured with the use of a quadrupole mass filter. In addition, an optogalvanic system is described, which was used to calibrate the wavelength of the RIMS resonance to an accuracy of 0.013 nm.