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Virtual Journal for Biomedical Optics

Virtual Journal for Biomedical Optics


  • Editor: Gregory W. Faris
  • Vol. 2, Iss. 8 — Aug. 10, 2007

Effective medium theories for irregular fluffy structures: aggregation of small particles

Nikolai V. Voshchinnikov, Gorden Videen, and Thomas Henning  »View Author Affiliations

Applied Optics, Vol. 46, Issue 19, pp. 4065-4072 (2007)

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The extinction efficiencies as well as the scattering properties of particles of different porosity are studied. Calculations are performed for porous pseudospheres with small size (Rayleigh) inclusions using the discrete dipole approximation. Five refractive indices of materials covering the range from 1.20 + 0.00 i to 1.75 + 0.58 i were selected. They correspond to biological particles, dirty ice, silicate, and amorphous carbon and soot in the visual part of the spectrum. We attempt to describe the optical properties of such particles using Lorenz–Mie theory and a refractive index found from some effective medium theory (EMT) assuming the particle is homogeneous. We refer to this as the effective model. It is found that the deviations are minimal when utilizing the EMT based on the Bruggeman mixing rule. Usually the deviations in the extinction factor do not exceed 5 % for particle porosity P = 0 0.9 and size parameters x porous = 2 π r s, porous / λ 25 . The deviations are larger for scattering and absorption efficiencies and smaller for particle albedo and the asymmetry parameter. Our calculations made for spheroids confirm these conclusions. Preliminary consideration shows that the effective model represents the intensity and polarization of radiation scattered by fluffy aggregates quite well. Thus the effective models of spherical and nonspherical particles can be used to significantly simplify the computations of the optical properties of aggregates containing only Rayleigh inclusions.

© 2007 Optical Society of America

OCIS Codes
(290.0290) Scattering : Scattering
(290.5850) Scattering : Scattering, particles

ToC Category:
Mass Spectrometry, Ignition, and Computational Analysis

Original Manuscript: October 31, 2006
Revised Manuscript: February 9, 2007
Manuscript Accepted: February 16, 2007
Published: June 12, 2007

Virtual Issues
Vol. 2, Iss. 8 Virtual Journal for Biomedical Optics

Nikolai V. Voshchinnikov, Gorden Videen, and Thomas Henning, "Effective medium theories for irregular fluffy structures: aggregation of small particles," Appl. Opt. 46, 4065-4072 (2007)

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