Light Absorbing Aerosols within Intense Laser Beams: Optical Effects, Morphology, and Composition

Earth's atmosphere often has 1000 – 10000 particles per cm³ and each particle has its unique composition, morphology, and exhibits special physical properties. One physical property of interest to our laboratory is light absorption. The experiments reported here involve the effects of laser illumination on different types of light absorbing aerosols. Samples considered include particles from candles, incense, a kerosene lamp, and biomass burning aerosols. Size distribution measurements are made with and without laser illumination to determine if the intense beam can induce changes. These measurements are combined with scanning electron microscopy measurements for further analysis of beam-induced morphology changes. It was found intense illumination can shift particle size distributions towards smaller diameters. Lastly, optical properties with and without laser illumination, including changes of extinction and scattering coefficients are measured by cavity ring down spectrometry (CRDS) combined with nephelometry at 532 nm. The results reported have implications for measurement of optical absorption by aerosols.