Anomalous diffraction approximation for light scattering cross section: Case of random clusters of non-absorbent spheres

Abstract

International audienceWe previously [Jacquier 5, Gruy F Approximation of the light scattering cross-section for aggregated spherical non-absorbent particles. JQSRT 2008;109:789-810] reformulated the anomalous diffraction (AD) approximation to calculate the light scattering cross section of aggregates by introducing their chord length distribution (CLD). It was applied to several ordered aggregates. This new method is entitled ADr, with. the r for rapid because this one is at least 100 times faster than the standard AD method. In this article, we are searching for an approximated expression for CLD suitable all at once for ordered and disordered aggregates. The corresponding scattering cross-section values are compared to the ones coming from the standard AD approximation

Geometrical Characterization of Various Shaped 3D-Aggregates of Primary Spherical Particules by Radial Distribution Functions

“…Characterization of aggregates with the same convex hull type and several shape ratios A similar inflection point can be remarked in the figure 12, which represents the results for aggregates with a cylindrical of convex hull, and different values for the k-parameter (1,2,8,20). Firstly, a proportionality between the largest inter-center distance values of each cylindrical convex hull aggregate and the k-parameter can be confirmed by the figure 12.…”

“…Concerning the discretization of the r value, the step between two r values is fixed to 20 nm, because it is the smallest distance between two particle centers, the radius of one particle being equal to 10 nm. Mathematically, the formula for the CRDF is defined by: CRDF (r) = N umber of particle centers at a distance ≤ r T otal number of particles in the aggregate (1) Since the aggregates have similar volume and are built along the same mesh, the focus has been placed on the particle mean number, normalized or not by the total number of particle within the aggregate. In Fig.5(a), it can be noticed that random filled aggregates are uniformely filled, because for each value of r, the ratios 50% and 75% are conserved between the concerned curves, until the r-value equal to the convex hull radius.…”

“…Indeed, the scattering parameter particularly depends on the internal and external geometry of the aggregates e.g. the chord length distribution (see, for instance Jacquier and Gruy [1]). The final aim of this study is to find a link between the underlying optical and morphological parameters.…”

Relationship between the morphology and the light scattering cross section of optically soft aggregates

“…Thus simple and accurate expressions for the optical properties of aggregates are needed. Simplified methods were developed for predicting the scattering and absorption cross sections of aggregates for several practical situations [12][13][14][15].…”