Time-integrated laser-induced plasma spectroscopy in the vacuum ultraviolet for the quantitative elemental characterization of steel alloys

This paper demonstrates that time-integrated space-resolved laser-induced plasma spectroscopy (TISR-LIPS) is a useful technique in the vacuum ultraviolet (VUV) for the quantitative determination of the carbon content in steels. The standard reference samples used were carbon-iron alloys containing a relatively wide concentration range of carbon (0.041-1.32%). In the experiments the output of a Q-switched Nd:YAG (1064?nm) laser, with approximately a 1?J maximum output pulse energy and approximately a 12?ns temporal pulse width, was focused onto the surface of each sample (under vacuum) in order to produce the emitting plasma. A fore-slit mounted in the target chamber allowed spatially-resolved spectral measurements in the axial direction of the plasma and provided emission lines that were almost free of the background continuum. A 1?m normal incidence vacuum spectrometer, equipped with a 1200 grooves mm-1 concave grating and a micro-channel plate/photodiode array detector combination, was used as the detection system. A particularly interesting feature of this work is the demonstration that VUV spectroscopy allows ionic lines to be used and linear calibration curves were obtained for the five carbon spectral lines (from C+ and C2+) under investigation. The limits of detection for all lines were determined; the lowest detection limit (87?10?ppm) was obtained from the C2+ 97.70?nm line, which compares favourably with the only available value in the literature of 100?ppm.