Aerosol measurement by laser-induced plasma technique: A review

Literature on laser-induced plasma spectroscopy (LIPS) published since the 1960s is reviewed and presented in this report, although LIPS of solid samples has been emphasized in the past. The LIPS is found to be the most convenient technique for in-situ and real-time measurement of metal species in the gaseous and aerosol phases. This technique is a strong candidate for the development of a next-generation field portable instrument for characterizing metal species from the emission sources as well as ambient environments. The instrument can provide a highly resolved spatial and temporal data of significance to environmental and health research on metal and particle toxicity. An instrument based on LIPS can be a viable tool for continuously monitoring toxic metal emissions at an industrial source, for example. The wide range of lasers used and other experimental and theoretical factors to be considered in the design of a LIPS instrument for aerosol measurements was discussed in this report. Experimental results from different studies on the high-energy laser interaction with aerosols and breakdown thresholds as a function of particle size, particle density, and wavelength are presented and the physical processes are discussed. Although it is not meant to be an exhaustive survey, this review serves as the basis for our ongoing development of a miniaturized LIPS-based instrument at the Oak Ridge National Laboratory.