Non-equilibrium and equilibrium problems in laser-induced plasmas

Abstract

Several problems which can determine non-equilibrium effects in laser-induced breakdown plasmas are analysed in this study. In particular, we focus our attention on problems associated with the fluid dynamics of the expanding plume, with time-dependent collisional-radiative models for describing the population densities of excited states, with the time-dependent Boltzmann equation for characterizing the electron energy distribution function in laser-induced breakdown spectroscopy (LIBS) plasmas. The results show that these problems should be carefully taken into account for developing a calibration-free LIBS methodology. Finally, problems associated with equilibrium plasmas, and in particular the dependence of the partition function on the particular environment surrounding the different components of a plasma are discussed.