A XeCl excimer laser (20 ns, 25 mJ) was focused on glass samples containing high concentrations of Li and K (10%, 15%, and 20%) in a surrounding gas of air and He. Plasma characteristics are compared in two cases: at 1 atm and at reduced pressure (1-10 Torr). It is shown that the plasma produced at 1 atm cannot be applied to the elemental analysis of solid samples because of strong background emission and self-absorption in the plasma. The spectrum width of the emission line is very wide due to strong interaction in the plasma. In contrast to this, the shock-wave-induced plasma produced at reduced pressure gives a high S/B (ratio of the intensity of the emission line to that of the background) in the measurement of analytical emission lines, and the slope of the calibration curve is near unity in a log-log plot, thus making it possible for emission spectrochemical analysis.
H. Kurniawan, K. Kagawa, M. Okamoto, M. Ueda, T. Kobayashi, and S. Nakajima, "Emission Spectrochemical Analysis of Glass Containing Li and K in High Concentrations Using a XeCl Excimer Laser-Induced Shock Wave Plasma," Appl. Spectrosc. 50, 299-305 (1996)