Aerosol Measurement by Laser-Induced Plasma Technique: A Review

Abstract

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 ® eld portable instrument for characterizing metal species from the emission sources as well as ambient environments. The instrument can provide a highly resolved spatial an d temporal data of signi® cance 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 an d 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.

Laser Induced Breakdown Spectroscopy

“…The use of LIBS for aerosol measurement has been reviewed by Martin et al 3 Since their survey, many efforts have been made to improve the quality of the results and to extend the use of LIBS to analysis of aerosols.…”

“…The instrument had a weight of 13.8 kg and a design very similar to the first portable instrument, fitting completely into a small carrying case of 48.3×33×17.8 cm 3 , but including an additional battery in the analysis unit for detector and electronics supply. It employed a Nd:YAG microchip laser source (1064 nm, 3.6 ns pulse duration, 21 mJ pulse energy, 1/3 Hz pulse repetition rate), a miniature spectrometer containing a grating spectrograph and a 2046 pixel non-gateable CCD, covering a spectral range of 123 nm with a resolution of 0.4 nm.…”

“…Song et al 6 have recently published a review specifically about the instrumentation used in LIBS, though several other reviews [1][2][3][4][5][6][7][8][9][10][11] about LIBS applications also discuss the instrumentation related to this technique. In addition, reviews about general spectroscopic instrumentation, detectors for spectrometry, and lasers are Figure 3.…”

“…The first portable LIBS instrument was developed at Los Alamos National Laboratory and reported by Yamamoto et al 167 The instrument had a weight of 14.6 kg, and fitted completely into a small carrying case of 46×33×24 cm 3 . It was composed of a sampling probe containing a flashlamppumped passively Q-switched Nd:YAG laser source (1064 nm, 4 to 8 ns pulse duration, 15 to 20 mJ pulse energy and 1 Hz pulse repetition rate), a focusing lens and an optical fiber cable to collect the emitted radiation, and an analysis unit containing the laser power supply (optionally a 12 V battery), a grating spectrograph, a 1024×256 pixel nongateable CCD, and a laptop computer.…”

“…The technique is named Laser Induced Breakdown Spectroscopy (LIBS) and numerous reviews [1][2][3][4][5][6][7][8][9][10][11] and three recent text books [12][13][14] have already been published addressing both general and specific aspects, in the relatively short period after the technique had undergone a renewed interest in the beginnings of the eighties. On the other hand, the technique has recently experienced an exponential growth in interest, reflected by an increasing number of publications, and, apparently, its niche in the general field of Analytical Chemistry are ready to be defined.…”