PNNL

Abstract

The effects of light scattering and refraction make it challenging to identify aerosolized chemicals using traditional spectral methods and (transmission) reference libraries. Due to an infinite number of aerosol sizes, shapes and compositions, constructing a database of laboratory-measured reference spectra is not feasible. As an alternative approach, the measured n/k optical spectra can be used in combination with photon absorption / scattering theory and the Beer-Lambert law to generate a series of synthetic infrared transmission / scattered light spectra. These synthetic spectra show that aerosol particle spectral signatures, for either transmission or scattering measurements, have distinct overall shapes as well as shifted peak positions and amplitudes compared to the reference data from bulk transmission measurements. To validate our synthetic signatures based on the derived n/k values, well-characterized aerosols of dioctyl sebacate are generated, and the spectral transmittance data are recorded for comparison.