Measured Infrared Absorption and Extinction Cross Sections for a Variety of Chemically and Biologically Derived Aerosol Simulants

Report No. ARL-TR-3253
Authors: Kristan P. Gurton, Rachid Dahmani, David Ligon, Burt Bronk
Date/Pages: June 2004; 22 pages
Abstract: In an effort to establish a more reliable set of optical cross sections for a variety of chemical and biological aerosol simulants, we have developed a flow-through photo-acoustic system capable of measuring the absolute, mass-normalized, extinction and absorption cross sections. By employing a flow-through design, we avoid issues associated with closed aerosol photo-acoustic systems and improve sensitivity. Although the results shown here were conducted over the tunable carbon dioxide laser waveband region (i.e., 9.20 to 10.80 *micro;m), application to other wavelengths is easily achievable. Aerosols considered are categorized as biological, chemical, and inorganic in origin, i.e., bacillus subtilis endospores, dimethicone silicone oil (SF-96 grade 50), and Kaolin clay powder (alumina and silicate), respectively. Results compare well with previously measured spectral extinction using Fourier transform infrared spectroscopy. Comparison with Mie theory calculations based on previously published complex indices of refraction and measured size distributions is also presented.
Distribution: Approved for public release
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Last Update / Reviewed: June 1, 2004