Depth-dependent calibration for quantitative elemental depth profiling of copper alloys using laser-induced plasma spectroscopy

This work presents new calibration procedures for deep elemental depth profile analysis of bronze artifacts. A simple ablation model is developed for the estimation of the ablation rate and hence for deriving the depth spatial calibration scale. Elemental quantification is obtained through the construction of calibration surfaces, using reference samples of known composition, relating laser-induced plasma spectroscopy (LIPS) intensity ratios, content of atomic species and number of laser pulses. Such a method represents a refinement of the standard LIPS quantification approach based on calibration curves, which is extended here to the generation of significantly deep craters into the material under investigation up to several hundred microns. The depth dependence of the calibration surfaces measured is discussed in the framework of a simplified model of depth-dependent plasma temperature.