On the quasi-universality of the forward light scattering lobe for micrometric objects

A quasi-universality property of Mie scattering was reported in a recent publication by C.M. Sorensen [J. Quant. Spectrosc. Radiat. Transf. (2013) 131, 3]: the authors represent the forward scattered intensity, normalized by the differential Rayleigh cross section, as a function of the coupling parameter. Here we provide clear experimental evidence of this result; the Sorensen plots are produced without any free parameter for pure water droplets suspended in air and oil-in-water emulsions measured by the Single Particle Extinction and Scattering method. In addition, as inferred by Sorensen, we find that non-spherical objects deviate from the quasi-universality behavior of spheres by applying the same approach to mineral dust. Notably, the larger discrepancies occur in the wavelength-scale size range. These plots can widen the field of diagnostics in the critical micrometric size range.