Light scattering by arbitrary shaped particles with rough surfaces: Sh-matrices approach

We continue to develop a modification of the T-matrix method that allows efficient studies of scattering properties of ensembles of independent irregular particles of different size. The advantage of the modification is quick calculations using the so-called shape-matrices (Sh-matrices), which allow more rapid calculations of particles of different size and can be used for averaging scattering properties over particle size. We extend this approach to light scattering by arbitrarily shaped particles with rough surfaces, including rough cubes and Gaussian spheres. Calculations of circular polarization ratio μC for small particles of different shape and roughness show conspicuous surges at low phase angles <10° that cannot be treated as a manifestation of the coherent backscattering effect. This contradicts the Hapke et al. (Icarus 1998;133:89) interpretation of the μc effect found for the lunar regolith that includes both large particles which are mainly aggregates of small grains and a significant portion of dust.

► We extend Sh-matrix methods to particles having irregularly rough surfaces. ► We perform calculations for rough spheres, cubes, and Gaussian spheres. ► Calculations of circular-polarization ratio show surges at low phase angles.