Investigation of lamp chemical composition by laser-induced breakdown spectroscopy

Summary form only given, as follows. The utilization of laser-induced breakdown spectroscopy (LIBS) as a non-destructive experimental diagnostic for studying lighting devices is discussed. LIBS involves the creation of a small plasma localized at the focus of a pulsed laser beam, and corresponding analysis of the spectrally dispersed radiation from the plasma. LIBS has been used as a method for determining the minority elemental composition of various types of samples. This work is aimed at applying LIBS to the species of interest found in metal halide discharge lamps. A 532 nm, 3 ns FWHM pulse from a Nd:YAG laser was used to produce a localized plasma in the interior of a vitreous silica tube containing mercury and sodium-scandium iodides, while the tube was maintained at operating temperatures in an oven. Spectral features corresponding to Hg, Na and Sc atomic emission were observed, originating from the evaporated fill chemicals. Time-resolved spectroscopy was used to record emission spectra at delay times on the order of a few microseconds following the laser pulse.