Laser induced plasmas at different nebulization conditions: Spatio-temporal distribution of emission signals and excitation temperatures

Abstract

CaF emission measurements are currently employed for indirect determination of fluorine concentration in solid samples using LIBS. This approach provides more sensitivity and improved limits of detection in comparison to the use of F atomic emission lines in the IR region, for quantitative purposes. Moreover, in Ca-free samples, the simultaneous nebulization of a Ca-containing solution during LIBS analysis was successfully proposed as a method to obtain the CaF emission, and indirectly determine the F concentration. Nevertheless, further insights are still required to understand the interaction of the laser-induced plasma with the nebulized solution. Therefore, in this work, the general effects of different nebulization conditions on a laser induced plasma are investigated in terms of variations in the plasma plume shapes, emission intensities and excitation temperatures. In particular, four different conditions are evaluated using Cu matrix as a model sample (i.e. non-nebulized sample, Ar nebulization, water nebulization and Ca-containing solution nebulization). Significant changes were shown under the Ca-solution nebulization, including a modification of the intensity decays of the Cu lines, lower average Cu excitation temperatures independently of the temporal window investigated, increased ablation rates, a huge asymmetry of the excited species in the plasma plume, and a partial detachment of the plume.