Elemental analysis of obsolete brittle metal samples using a two-pulse laser spectrometer

Abstract

The possibilities of using laser induced breakdown spectroscopy for elemental analysis of multicomponent metal iron age artefacts are studied. Much attention is paid to the influence of dirt, patina, rust, scale on the process of laser ablation, and, as a result, on the relative intensity of spectral lines. A method is proposed to estimate the thickness of molecular compounds on the surface of metal artifacts to subsequently exclude the corresponding spectral data from the analysis results. It has been found that during laser ablation of pure metal samples at fixed radiation parameters, the relative intensity of spectral lines during ablation of a modern sample can significantly (up to 30 %) exceed the intensity for an old sample that has been underground for a long time. Thus, a quantitative analysis using calibration curves, built on the basis of modern standard samples, will lead to incorrect results. In this case, the transition from single-pulse to double-pulse laser ablation, which leads to a multiple increase in the relative intensity of spectral lines, is very important, since it allows one to significantly increase the sensitivity of the analysis and reduce the error.