Plasma volume considerations for analysis of gaseous and aerosol samples using laser-induced breakdown spectroscopy

Three distinct characteristic plasma volumes were experimentally measured and are discussed in the context of the analysis of gaseous and aerosol systems using laser-induced breakdown spectroscopy. The resulting statistical sample volume, emission-based plasma volume, and the physical plasma volume, range between 1.2 × 10^-3 and 2.4 × 10^-3 cm³, and the variations are interpreted in terms of the intrinsic behavior of laser-induced plasma-particle interactions. Due to plasma non-homogeneity, the particle vaporization necessary for subsequent detection is limited to a plasma region somewhat smaller than the region defined by the physical plasma volume based on optical absorption. In contrast, the emission-based plasma volume, the largest of the three recorded volumes, reflects analyte emission following particle vaporization and diffusion, and is considered in terms of an equivalent emitting plasma volume.