Abstract

In this Letter, we numerically calculate the mass absorption cross sections (MACs) of black carbon fractal aggregates in the thermal infrared solar spectrum. Compared to equivalent-size spheres, the MAC values of aggregates show a percent enhancement of $\approx 150$ and 400 at small and large length scales, respectively. The absorption properties of aggregates with size parameters $>1$ surprisingly continued to remain in the Rayleigh optics regime. We explain this phenomenon using the Maxwell–Garnett effective medium theory and the concept of phase shift parameter.

© 2016 Optical Society of America

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