The Relationship of Spectral Line Intensity to the Weight of Sample Vaporized with the Laser Microprobe

Abstract

Emission spectra excited by the laser microprobe are less subject to the influence of the matrix than when excitation is by conventional modes such as a dc arc. Statistical correlations show that the measured spectral line intensity is a function of the weight of material vaporized when the laser is used. Several important factors must be considered to obtain such results with the laser. The size and dimensions of the laser craters (pits) must be carefully measured to determine concentrations since the crater sizes vary from material to material. Crater dimensions may be determined relatively easily by optical microscopy and serve as a method of standardization among materials. The laser energy must be carefully focused to produce a crater which is essentially conical. This not only facilitates microscopic measurements but insures complete sample vaporization. Also, the amount of material deposited around the crater (and probably not reaching the spark discharge) is shown to be minimal in most cases.