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Title: Light Scattering Study of Highly Absorptive, Non-fractal, Hematite Aggregates
We present measurements of the scattered light intensity by aerosolized hematite aggregate particles. The measurements were made at a wavelength of 532 nm in the scattering angle range from 0.32 °to 157 °. Hematite has high values of the real and imaginary parts of the refractive index m = n + i κ= 3 + i0.5 at the studied wavelength. Scanning electron micrographs (SEM) indicated that the particles were aggregates whereas the optical microscope pictures showed that the aerosol had a bimodal distribution with effective mean diameters of roughly 1 and 10 μm. This is consistent with the light scattering results which displayed two Guinier regimes. The aggregates were composed of smaller grains with an approximate size of 200 nm. Ultra Small-Angle X-ray Scattering (USAXS) indicate that the aggregates were uniform and non-fractal. Mie calculations for a sphere equivalent to the aggregate size 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. Hematite aggregates were simulated by assuming they were composed of spherical monomers inside a spherical volume. Then the light scattering was calculated using the T-matrix method for these simulated aggregates. The calculated results show an enhanced backscattering. We present a dimensional analysis to estimate the extent of multiple scattering within the aggregate and find a correlation between the average number of scattering events within the aggregate and the enhancement in the backscattering.  more » « less
Award ID(s):
1649783
NSF-PAR ID:
10159750
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Journal of quantitative spectroscopy and radiative transfer
Volume:
246
ISSN:
0022-4073
Page Range / eLocation ID:
106919
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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