Two-lines method for estimation of plasma temperature and characterization of plasma parameters in optically thick...

In this paper, the characteristics of laser-induced plasmas are studied by investigation of the spectral line features in laser-induced breakdown spectroscopy (LIBS) experiments. The plasma is produced by focusing of a Nd:YAG laser on standard Al-alloy samples at 30 mJ energy. Here, with the assumption of having a homogenous plasma and by using a semiemperical technical method, the plasma temperature is calculated by the proposal of a new two-lines method. Moreover, by utilizing some theoretical equations, the plasma parameters and the self-absorption magnitude are evaluated according to the radiative transfer equations in local thermodynamic equilibrium (LTE) conditions. The main advantages of this method are that without discrimination between thin plasmas and thick ones, and as well as without straight quantification of the degree of self-absorption, the plasma temperature can be calculated. The results showed that determination of the intensities of the spectral lines, transition parameters, and Stark broadening parameter is adequate for plasma characterization in a typical LIBS experiment.