Emission spectroscopy of long cylindrical laser spark with additional coaxial excitation

Abstract

Low intensity lines of elements with high excitation potentials, especially non-metals, is one of the main problems of laser-induced breakdown spectroscopy (LIBS). To our knowledge, we report the first combination of long spark produced by a cylindrical lens with an additional orthogonal excitation along the long axis. We studied temporal evolution of the plasma parameters at delays in the range of 100 to 500 ns and inter-pulse delays of 600 to 1800 ns. This variant of double pulse LIBS leads to the formation of a rather large (approx. 14 mm length) and hot laser-induced plasma, (2.0–3.8) × 104 K, with a relatively low electron density, (2–8) × 1017 cm−3. Our analysis reveal that the proposed optical configuration provides the optimal conditions for observing ionic lines with high excitation potentials in comparison with the conventional LIBS arrangement.