Analysis of aerosols by LIBS

Laser-induced breakdown spectroscopy (LIBS) is well suited for the analysis of aerosol particles because of the unique point sampling nature of the laser-induced plasma. The discrete plasma volume uniquely couples with the discrete nature of aerosol particles to enable a wide range of data analysis options, including spectral averaging, conditional spectral processing, and single-shot analysis. In this chapter, a detailed introduction to aerosol science and aerosol analysis is presented to frame the overall problem of LIBS-based aerosol analysis. A detailed analysis of the laser-induced breakdown process is focused on the gas-phase processes associated with plasma initiation and propagation. Quantitative aerosol analysis is presented in terms of the aerosol-sampling problem, followed by direct and indirect quantitative aerosol measurements. We conclude with a detailed discussion of LIBS applications to aerosol analysis and future directions in this challenging and important area.

Aerosols (Latin, Aer (air) and sole (solutions)) are particle ensembles of solid and/or liquid matter with characteristic dimensions in the nanometer to micrometer range suspended in a gaseous carrier gas. Common usage, however, refers to aerosols often only as the particulate component. For many processes involving semivolatile components, the gas phase is, however, inextricably linked to the particle composition. In relation to their number density, aerosols are ubiquitous; however, the mass of a single aerosol particle is often negligibly small. For example, a solid spherical particle of 100 nm diameter with a density of 2 g cm−3 has a total mass of 1 fg.