Calibration-free laser-induced plasma analysis of a metallic alloy with self-absorption correction

Identification and concentration measurement of constituent elements of a metallic alloy is demonstrated by calibration-free laser-induced breakdown spectroscopy (CF-LIBS) according to a special peak intensity-based model and considering the self-absorption effect. In this procedure, which is based on the line pair ratio method, the effect of line widths, though needs to be theoretically considered, may be approximately ignored. This is mainly true for the multiplet lines, but this property, in the case of some generic spectral lines in a measured spectrum, can be sometimes regarded. Initially, the optical penetration depth and therefrom self-absorption coefficient of each selected spectral line is calculated using the experimental (self-absorbed) intensity of the line. Then, the true (non-self-absorbed) intensity, which is basis of the conventional CF-LIBS calculation, is obtained through a recursive algorithm implemented by the MATLAB programming. In the experimental examination, the recorded spectrum reflects that the metallic alloy is consisted of gold, copper and silver. The concentration of elements is calculated with and without regarding self-absorption correction using 27 trios of spectral lines related to the elements. The average concentrations signify that the measurement error relative to the certified value for the concentration of the gold is modified from 3.56 % in the normal way to 0.34 % after applying self-absorption correction.