Approximation for the light scattering cross-section of optically hard aggregates

The light scattering cross-section of a certain class of aggregates is calculated by GMM theory. The aggregates are submicronic and are allowed to have various shapes. They consist of N spherical particles. The material is non-absorbing and optically hard. 1792 aggregates with N>13 have been studied. The varied parameters are the shape and the size parameters of the aggregate hull, the volume fraction of matter in the aggregate, the refractive index of the material and the light wavelength in the visible range. The scattering cross-section that strongly deviates from the Rayleigh approximation obeys a new approximate expression with an accuracy of 8.4%. The latter is based on the effective medium theory–Mie theory that is modified by considering two additional aggregate parameters: the volume fraction of matter and the first moment of the distance distribution function. ► Submicronic aggregates with high refractive index are considered. ► Light scattering cross-section is calculated. ► Empirical expressions linking scattering properties, geometrical and optical parameters are proposed.