Study of Laser-Induced Breakdown Emission From Liquid Under Double-Pulse Excitation

The application of laser-induced breakdown spectroscopy to liquid samples, by use of a Nd:YAG laser in doublepulse excitation mode, is described. It is found that the line emission from a magnesium ion or atom is more than six times greater for double-pulse excitation than for single-pulse excitation. The effect of interpulse separation on the emission intensity of a magnesium ion and a neutral atom showed an optimum enhancement at a delay of 2.5 – 3 (mu)s. The intensity of neutral atomic line emission dominates the ion emission from the plasma for higher interpulse ( >10 (mu)s) separation. A study of the temporal evolution of the line emission from the plasma shows that the background as well as line emission decays faster in double-pulse excitation than in single-pulse excitation. The enhancement in the emission seems to be dominated by an increase in the volume of the emitting gas. The limit of detection for a magnesium solution improved from 230 parts per billion (ppb) in single-pulse mode to 69 ppb in double-pulse mode