The effects of laser energy and atmosphere on the emission characteristics of laser-induced plasmas were studied with the use of a Q-switched Nd:YAG laser over a laser energy range of 20 to 95 mJ. Argon, helium, and air were used as surrounding atmospheres, and the pressures were changed from atmospheric pressure to 1 Torr. The experimental results showed that the maximum spectral intensity was obtained in argon at around 200 Torr at a high laser energy of 95 mJ, whereas the line-to-background ratio was maximized in helium at around 40 Torr at a low energy of 20 mJ. The results are discussed briefly on the basis of the temporal and spatial observations of the laser-induced plasmas.
Mikio Kuzuya, Hitoshi Matsumoto, Hideaki Takechi, and Osamu Mikami, "Effect of Laser Energy and Atmosphere on the Emission Characteristics of Laser-Induced Plasmas," Appl. Spectrosc. 47, 1659-1664 (1993)