A Laser Induced Breakdown Spectroscopy application based on Calibration Free method and localThermodynamic Equilibrium assumption for the elemental analysis of Alexandrite gemstone and copper based alloys.

Laser Induced Breakdown Spectroscopy (LIBS) is an appealing technique tostudy laser-induced plasmas (LIPs) both from the basic diagnostics point of view and for analytical applications. LIPs are complex dynamic systems, expanding at supersonic velocites and undergoing a trasnsition between different plasma regimes. If the Local Thermodynamic Equilibrium (LTE) conditin is valid for such plasmas, several analitical methods can be employed and fast quantitative analyses can be performed on a variety of samples. In the present paper, a discussion about LTE is carried out and an innovative application to tht analysis of the alexandrite genstone is presented. In addition, a study about the influence of plasma parameters on the performance of LTE-based methods is reported for bronze and brass targets.