Pressure effects on underwater laser-induced breakdown spectroscopy: an interpretation with self-absorption

Abstract

Laser-induced breakdown spectroscopy (LIBS) has been successfully applied for in situ detection in the sea, and the water pressure is found to be the main influence on the LIBS signal compared to temperature or salinity. In this study, we explored self-absorption to evaluate the pressure effects on LIBS detection. By using fast imaging and spectroscopic technique, it is proved that self-absorption (SA) was significantly enhanced with increased pressure, and the severe inhomogeneity of plasma distribution might be the reason. With this SA model, the LIBS intensity could be well-estimated according to the simulation results. Moreover, the self-absorption of LIBS underwater was more likely determined by the plasma temperature when the detection was carried out in a low-pressure regime. The obtained results would be helpful for the signal correction of LIBS in the deep sea.