AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
The Light Scattering Study of Highly Absorptive Hematite Aggregates
PRAKASH GAUTAM, Justin Maughan, Christopher Sorensen, Kansas State University
Abstract Number: 135 Working Group: Aerosol Physics
Abstract We present a measurement of the light scattering of highly absorptive hematite particles, which have agglomerated irregular shapes. The measurements were made at a wavelength of 532 nm in the scattering angle range from 0.3° to 158°. Hematite is important from a light scattering point of view because it has high values of the real and imaginary parts of the refractive index m = n + ik = 3 + i0.5 at the studied wavelength. Scanning electron micrographs are used to determine size distribution. The mean aggregate size is 4-5 micron, roughly a diameter, and the aggregate is composed of smaller grains with approximate size of 200 nm. Mie calculations for a sphere equivalent to the aggregate size of hematite particles were compared to the experimentally observed results. The observed results showed an enhanced backscattering, whereas the Mie calculations did not due to the large imaginary part of the refractive index. We simulated the agglomerate hematite particles by assuming it was composed of spherical monomers inside a spherical volume. Then the light scattering was calculated using the T-matrix method. The calculated results showed an enhanced backscattering. This suggests that an enhancement in the backscattering is due to the effect of multiple scattering between the grains within the aggregates.