Multi-pulse laser-induced plasma spectroscopy using a single laser source and a compact spectrometer

A portable laser induced breakdown spectrometer (LIBS), built around a microscope using a Q-switched Nd: GGG laser releasing multiple pulses and a non-intensified fiber optic spectrometer, was used to investigate the signal improvement of emission data achievable by the multiple-pulse approach. LIBS experiments were carried out in air and using Al, Cu, Si and Zn metallic targets. It was found that the use of 7 laser pulses, separated by ca. 25 ms time intervals, enhance line emissions by a factor of 2.5 to 129 with respect to the single-pulse case, and also decrease the relative standard deviation of the signal based on five consecutive measurements to 2 - 5%. Time-resolved emission data and the observation of ablation craters suggest that the signal enhancement is mainly attributable to the reheating of the plasma by multiple laser pulses.