RESUMO
The branching ratio method is usually used to evaluate the optical thinness conditions in laser-generated plasmas, which are important for the application of analytical methods such calibration free laser induced breakdown spectroscopy (CF-LIBS). In this communication, we warn on the possibility that in some circumstances, the branching-ratio method might give results close to the one characterizing optically thin plasma conditions, even in the presence of a substantial self-absorption for the transitions considered.
RESUMO
In this paper we present a new method for determining the self-absorption coefficients of emission lines in laser-induced breakdown spectroscopy (LIBS) experiments. With respect to other methods already present in the literature, the proposed approach has the advantage of not requiring, providing some conditions are fulfilled, any knowledge of the plasma parameters such as temperature and electron number density and of the emission line spectral coefficients such as transition probability. An example of the application of the approach is given for emission lines measured at different delay times after laser ablation of a silver target.
