Laser-induced Plasma Spectroscopy using Infrared CO ₂ Laser and its Applications for Elemental Analysis

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A review of a study on laser-induced plasma spectroscopy using a transversely excited atmospheric (TEA) CO₂ laser has been presented. This study was divided into two parts: the first part involves the shock wave plasma induced by a TEA CO₂ laser, which is induced under a low-pressure ambient gas at 1 Torr. The other part involves producing metal-assisted gas plasma under atmospheric pressure, induced by a transversely excited atmospheric CO₂ laser. Time-resolved spatial distribution and plasma dynamics have been studied in detail using unique experiments. Furthermore, the shock wave model was also presented. Some applications of the shock wave plasma include highly sensitive analysis in solid samples and films attached to the substrate. The TEA CO₂ laser-induced gas plasma highlights numerous advantageous features, such as a high temperature of approximately 7000 K, exceptional uniformity in the plasma density, a relatively low plasma density, and an exceptionally high heat capacity. One of its applications is the direct analysis of powder samples. Furthermore, it is confirmed that the TEA CO₂ laser bombardment produces a large number of He metastable atoms in the He gas plasma. The analytical emission exhibits distinct characteristics, including narrow spectral width, strong intensity, low background, and long lifetime. This, in turn, validates the excitation process facilitated by helium metastable atoms. The novel applications of "selective detection of H" in metal samples using TEA CO₂ laser-induced He gas plasma have been emphasized.