Impact of particle shape on refractive-index dependence of scattering in resonance domain

The impact of particle shape on how scattering, in particular the asymmetry parameter g, depends on the refractive index m is studied. Light scattering simulations for spheres and 16 different spheroids with varying refractive indices and sizes are carried out using an exact T-matrix method to establish how m affects scattering for different shapes. In addition to single shapes, shape distributions of spheroids are used to mimic scattering properties of ensembles of irregularly shaped particles. The results show that Δg resulting from Δm are both size and shape dependent, and spheroids are not universally less or more sensitive to m than the corresponding spheres are. While shape distributions of spheroids show much weaker and much more consistent m-dependence of g than the spheres of the same size, an integration over a size distribution (SD) largely eliminates these differences. Thus, the use of spheres for estimating Δg resulting from Δm for a collection of nonspherical particles appears to be safe except for very narrow SDs. The actual g-values tend to be, however, considerably and consistently in error.