Investigation on self-absorption reduction in laser-induced breakdown spectroscopy assisted with spatially selective laser-stimulated absorption

The method of spatially selective laser-stimulated absorption (SS-LSA) was proposed to reduce self-absorption in laser-induced breakdown spectroscopy (LIBS). Through scanning intensity maps of analytes, it was discovered that elemental distribution was inhomogeneous in the formed plasma. Taking copper (Cu) and chromium (Cr) elements in steel as examples, the distribution of Cu and Cr has its own characteristics. By focusing the laser beam on the optimal locations of the plasma with an optical parametric oscillator (OPO) wavelength-tunable laser, the linear determination coefficient (R-2 factor) for Cu and Cr elements can reach 0.993 and 0.999, respectively. For Cu determination, compared with LIBS and LSA-LIBS, the root-mean-square error of cross-validation (RMSECV) of SS-LSA-LIBS decreased by 81 and 52%, respectively. The analytical accuracy of the quantitative analysis was much higher than those of conventional LIBS and LSA-LIBS, which indicates that the proposed method can effectively reduce self-absorption and improve LIBS analytical performance.