Search

Abstract: Light scattering is an useful tool for the detection and characterization of different types of particles and simulation of the scattering process can help to understand the scattering characteristics. To simplify the computational simulation often axis-symmetric particles are used, while in reality particles usually do not show such simple structures. To cope with this, advanced methods and algorithms are needed. In this paper we investigate the scattering characteristics by spherical particles with a rough surface, which therefore are non-symmetrical. The light scattering diagrams by these complex structured particles are computed using the nullfield method with discrete sources. The particle shape data is generated by computational methods; here we use the concept of Gardner Series to create spherical particles with a rough surface. [Copyright &y& Elsevier]

Abstract: The T-matrix method is particularly useful for modeling light scattering by mesoscale particles under non-plane wave illumination. Its main advantage lies where repeated calculations with different incident conditions are required, e.g. as particles move through a focused beam, or are optically trapped by a beam. The extended boundary condition method (EBCM) is the most commonly used method for calculating a T-matrix. However, the conventional EBCM is limited to modeling particles that are isotropic and homogeneous. Because scattering by anisotropic and inhomogeneous particles is of practical interest, we have implemented an FDFD T-matrix hybrid method. [Copyright &y& Elsevier]

Abstract: A computer code is described for the calculation of light-scattering properties of randomly oriented, axially symmetric coated particles, in the framework of the T-matrix theory. The underlying mathematical background is outlined briefly and convergence procedures are discussed. After outlining the input–output interaction between user and code, benchmark results are presented for two distinct shapes: coated, centered spheroids and offset coated spheres. [Copyright &y& Elsevier]

Abstract: This paper investigates the single-scattering properties of elongated hexagonal ice columns in random orientation. The calculation of these properties becomes more challenging with electromagnetic methods as the aspect ratio and/or the size parameter of the particles increases. The results presented in this paper have been obtained with a new version of a T-matrix implementation which uses only variables of data type real. This re-formulation makes it possible to run the code on a DEC Alpha workstation in quadruple precision. With the increased numerical precision aspect ratios of 10 are obtained at moderate size parameters. The single-scattering properties of elongated hexagonal columns are compared against those of various other particles. Circular cylinders of the same aspect ratio and surface area have quite similar single-scattering properties. They agree well in all phase matrix elements and the extinction efficiency and asymmetry parameter are within 25% and 5%, respectively. The single-scattering properties of elongated hexagonal columns are very different to those with equal surface-area and aspect ratios around unity. The extinction efficiencies of the more compact particles are several times larger than those of the elongated columns and the phase matrix elements are very different. The spheres of equal volume and equal surface area do not mimic the single-scattering properties of elongated hexagonal columns either. The agreement with the smaller sphere of equal volume-to-surface-area ratio is reasonable. It is found that for hexagonal columns with increasing aspect ratios, all phase matrix elements except the phase function converge to the Rayleigh solution. The results of this paper imply that such scattering behaviour, previously demonstrated for elongated spheroids, is more general and does also apply to faceted objects like hexagonal columns. [Copyright &y& Elsevier]

A procedure for analytical averaging of the attenuation and scattering cross sections for systems of chaotically oriented axially symmetric particles was developed for the first time within the framework of the modified T-matrix method and the method of separation of variables for spheroids. These approaches essentially complement each other: one is applicable to axially symmetric scatterers of different shape but is inefficient if the ratio of the maximum to the minimum size of the particles exceeds 3–5; the other is applicable only to spheroids, but the ratio of the major semiaxis to the minor one can be considerable, for example, 100 and larger. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]