INFRARED PROPERTIES OF ATMOSPHERIC AEROSOL CONSTITUENTS - POLYAROMATIC HYDROCARBONS AND TERPENES

The infrared spectra (2-20 mum) of six terpene samples and six polyaro matic hydrocarbon (PAH) samples are presented and compared with simila r spectra obtained from standard grade petroleum (fog oil) samples. Th e selected samples are representative of the various different molecul ar structures that may be present in atmospheric aerosol sources, part icularly fire smokes. Results are presented in terms of the wavelength -dependent complex refractive indices as obtained from bulk phase (thi n layer) transmittance measurements and the Kramers-Kronig relationshi ps. All samples exhibit a characteristic complex absorption spectra wi th numerous line absorption features in the 8-14-mum atmospheric windo w regions with peak imaginary indices nominally around 0.10-0.12 for t he terpene samples and on the order of 1.0-1.2 for the PAH samples, al though there are far fewer lines in the PAH samples than in the terpen e samples. The terpenes also exhibit absorption features in the 3-5-mu m window which are much like those found in the standard samples but a re not observed in the PAH samples.