Orthogonal and Collinear Configurations in Double-Pulse Laser-Induced Breakdown Spectrometry to Improve Sensitivity in Chlorine Determination

We consider collinear and orthogonal beam-convergence configurations in double-pulse laser-induced breakdown spectrometry (LIBS, also known as laser-spark emission spectrometry) for chlorine determination in plants and concrete from the Cl I 837.59 nm line. We have observed that the signal-to-noise ratio is not much lower for the orthogonal configuration due to spatial instability in the second breakdown. At the same time, suppression of interfering molecular bands in this configuration lets us improve the sensitivity of LIBS for chlorine determination in plant material.