Spectral enhancement mechanism and analysis of defocused collinear DP-LIBS technology

Abstract

Laser-induced breakdown spectroscopy (LIBS) is a modern analytical technique emerging in recent years, which widely used in qualitative and quantitative determination of various samples. However, because the plasma spectral enhancement mechanism of the two typical LIBS technologies(pre-ablation and reheating LIBS) varies greatly, how to choose the spectral enhancement solution and rationally configure the LIBS system in different applications still needs further research and discussion. In this paper, we constructed a defocusing collinear dual-pulse LIBS(DP-LIBS) experimental system, and carried out relevant experiments for pre-ablation and reheating plasma spectral enhancement, and studied separately the effects of ablation sampling, reheating and re-excitation of plasma in collinear DP-LIBS. The experimental results show that the pre-ablation defocus collinear DP-LIBS is an indirect spectral enhancement technology, which uses the pre-ablation laser to change the surface environment of the sample, so that the sample is more conducive to the excitation of plasma, thus achieving spectral enhancement. The spectral and ablative crater analysis of the reheating defocus collinear DP-LIBS show that it enhances the spectral signal by reheating and re-exciting the plasma by the second laser beam, which is a direct spectral enhancement technology and has better enhancement effect than indirect enhancement technologies such as pre-ablation DP-LIBS. In addition, the laser inter-pulse delay time is an important factor in maintaining the temperature of the plasma to sustain the atomic radiation. Under different spectral enhancement solution, proper configuration of laser inter-pulse delay time is the key factor to obtain high spectral intensity and good signal-to-noise ratio.