In situ Measurement of the Infrared Spectral Extinction for Various Chemical, Biological, and Background Aerosols

Report No. ARL-TR-3071
Authors: Kristan P. Gurton, David Ligon, and Rachid Dahmani
Date/Pages: September 2003; 22 pages
Abstract: We conducted a series spectral extinction measurements on a variety of aerosolized chemical and biological simulants over the spectral range 3?13 ?m using conventional Fourier transform infrared (FTIR) aerosol spectroscopy. Samples consist of both aerosolized particulates and atomized liquids. Materials considered include Bacillus subtilis endospores (BG), lyophilized ovalbumin, polyethylene glycol (PEG), dimethicone (SF-96 grade 50), and three common background materials (Kaolin clay [hydrated aluminum silicate], Arizona road dust [primarily SiO2], and diesel soot). Aerosol size distributions and mass density were measured simultaneously with the FTIR spectra. As a result all optical parameters presented here are mass-normalized, i.e., (m2/g). In an effort to establish the utility of using Mie theory to predict such parameters, a series of calculations were conducted. For materials in which the complex indices of refraction are known, e.g., silicone oil (SF-96 grade 50) and Kaolin, measured size distributions were convolved with Mie theory and the resultant spectral extinction calculated. Where there was good agreement between measured and calculated extinction spectra, absorption, total scattering, and backscatter were also calculated.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2003