Coherent backscattering by discrete random media composed of clusters of spherical particles

Abstract The approximate method of accounting for the weak localization effect in discrete random media makes it possible to calculate the intensity and the degree of linear polarization of radiation reflected by a semi-infinite layer containing randomly oriented clusters of identical nonabsorbing spherical particles. The paper is focused on the analysis of the influence of the medium properties – the concentration of the clusters, their structure, the sizes and the number of constituent monomers – on the phase dependence of the characteristics of the interference (coherent) component of radiation. Three types of clusters were chosen for the analysis: a fractal-like cluster and two random clusters with different packing densities of monomers. Three values of the size parameters of monomers were considered: 0.5, 1.0, and 1.5. The chosen values of the refractive index of monomers correspond to that of magnesium oxide in the visible spectral range. This allowed us to compare the theoretical phase curves of the degree of linear polarization of light reflected by the medium with the data of measurements by Lyot. For all of the considered cluster types, starting from some minimal number of constituent monomers, which is typical of the specified cluster's type and the monomer's size, the characteristics of the coherent component were found to be practically independent of the number of constituents. In particular, in the phase-angle range from 0° to 15°, the branch of negative polarization measured for a layer of magnesium oxide by Lyot can be well described with several models of the media containing either the fractal-like clusters or the random clusters with the packing density larger than 30%. In these models, the number and sizes of constituent monomers vary. To select from the whole set of “suitable” clusters those the optical characteristics of which actually correspond to characteristics of an elementary volume of the specified medium, additional information is required. For example, this can be the results of polarization measurements in a wider phase interval that includes a zone of the dominating influence of incoherent (diffuse) scattering.

[1]  E. V. Petrova,et al.  Modeling of opposition effects with ensembles of clusters: Interplay of various scattering mechanisms , 2007 .

[2]  G. Maret,et al.  Theoretical study of the coherent backscattering of light by disordered media , 1988 .

[3]  J. W. Chamberlain,et al.  Light Scattering in Planetary Atmospheres , 1976 .

[4]  K. Jockers,et al.  Optical properties of aggregate particles comparable in size to the wavelength , 2004 .

[5]  Henk A. van der Vorst,et al.  Bi-CGSTAB: A Fast and Smoothly Converging Variant of Bi-CG for the Solution of Nonsymmetric Linear Systems , 1992, SIAM J. Sci. Comput..

[6]  A. Takami,et al.  Morphological features of soot‐containing particles internally mixed with water‐soluble materials in continental outflow observed at Cape Hedo, Okinawa, Japan , 2011 .

[7]  D. Mackowski.  Electrostatics analysis of radiative absorption by sphere clusters in the Rayleigh limit: application to soot particles. , 1995, Applied optics.

[8]  D. Varshalovich,et al.  Quantum Theory of Angular Momentum , 1988 .

[9]  M. Mishchenko,et al.  Approximate calculation of coherent backscattering for semi-infinite discrete random media , 2009 .

[10]  Leung Tsang,et al.  Dense media radiative transfer theory based on quasicrystalline approximation with applications to passive microwave remote sensing of snow , 2000 .

[11]  Andrew A. Lacis,et al.  Scattering, Absorption, and Emission of Light by Small Particles , 2002 .

[12]  V. Tishkovets.  Multiple scattering of light by a layer of discrete random medium: backscattering , 2002 .

[13]  J. Piironen,et al.  The Opposition Effect and Negative Polarization of Structural Analogs for Planetary Regoliths , 2002 .

[14]  N. M. Shakhovskoy,et al.  Polarimetric remote sensing of Solar System objects , 2010, 1010.1171.

[15]  A. Lacis,et al.  Multiple Scattering of Light by Particles: Radiative Transfer and Coherent Backscattering , 2006 .

[16]  K. Jockers,et al.  Polarization of Light Scattered by Solar System Bodies and the Aggregate Model of Dust Particles , 2004 .

[17]  Magnesium Oxide (MgO) , 1997 .

[18]  M. Mishchenko,et al.  A multiple sphere T-matrix Fortran code for use on parallel computer clusters , 2011 .

[19]  Coherent backscattering of light by a layer of discrete random medium , 2004 .

[20]  M. Mishchenko,et al.  COHERENT BACKSCATTERING VERIFIED NUMERICALLY FOR A FINITE VOLUME OF SPHERICAL PARTICLES , 2012 .

[21]  Pavel Litvinov,et al.  Coherent backscattering effects for discrete random media : Numerical and theoretical results , 2007 .

[22]  Michael I. Mishchenko,et al.  Scattering of electromagnetic waves by ensembles of particles and discrete random media , 2011 .

[23]  K. Jockers,et al.  A Negative Branch of Polarization for Comets and Atmosphereless Celestial Bodies and the Light Scattering by Aggregate Particles , 2001 .