Application of Laser Ablation–Laser Induced Fluorescence Spectroscopy to Analysis of Steel

—Detection of Low Carbon in Steel—

Abstract

Fluorescence of atomic carbon in steel was detected at 193.09 nm by the excitation with laser pulse tuned at 247.85 nm. Solid steel samples were irradiated by pulsed Nd:YAG laser (ablation laser) to generate atomic vapor, which was then illuminated by the probe laser. One of ionic iron lines is very close to the excitation line for carbon. However, its interaction was not found to be very significant because population of ionic iron decreased faster than that of atomic carbon in a transient plasma induced by the ablation laser. When the probe laser was coaxial with the ablation laser, fluorescence spectra with high selectivity was observed with delay of 50 μs between two lasers. Fluorescence intensities were in a good linear correlation with contents of carbon in steel samples in a range of 83–5000 μg/g, which suggested that quantitative detection of carbon would be possible with the developed method.