Scattering from arbitrarily shaped particles: theory and experiment

We present a review of the discrete dipole approximation (DDA), which is a general method to simulate light scattering by arbitrarily shaped particles. We put the method in historical context and discuss recent developments, taking the viewpoint of a general framework based on the integral equations for the electric field. We review both the theory of the DDA and its numerical aspects, the latter being of critical importance for any practical application of the method. Finally, the position of the DDA among other methods of light scattering simulation is shown and possible future developments are discussed.

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“…(13), as compared to Eq. (14). It results in even better accuracy than CEMD, but at the expense of additional computation time.…”

Section: Modifications and Extensions Of The Ddamentioning

confidence: 98%

“…The remaining integral was evaluated by approximating the cube by a volume-equivalent sphere, resulting in ( ) ( ) was performed by Livensay and Chen [36] and implemented into the DGF formulation of the DDA by Hage and Greenberg [14,35] and later Lakhtakia [37]:…”

Section: General Frameworkmentioning

confidence: 99%

The discrete dipole approximation: An overview and recent developments

Yurkin

Hoekstra

2007

Journal of Quantitative Spectroscopy and Radiative Transfer

775

458

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“…Dependence of P(160°) on n cut for a cube with kD = 8 and m = 1.6 + 0.01i computed with the T-matrix method. Fitted curves and estimated confidence ranges are shown, derived from two subsets of data -n cut ∈ [15,40] (default) and [20,35]. The DDA result (extrapolated) is shown for reference; its estimated uncertainty is less than line width (see Fig.…”

Section: P(160°)mentioning

confidence: 99%

“…Limited comparisons of the DDA with independent methods at that time [20,21] achieved relative differences between 1% and 10% depending on the refractive index.…”

Section: Introductionmentioning

confidence: 99%

Light scattering by a cube: Accuracy limits of the discrete dipole approximation and the T-matrix method

Yurkin

Kahnert

2013

Journal of Quantitative Spectroscopy and Radiative Transfer

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Citation for the published paper: Yurkin, M. ; Kahnert, M. (2013) "Light scattering by a cube: Accuracy limits of the discrete dipole approximation and the T-matrix method". Journal of Quantitative Spectroscopy and Radiative Transfer, AbstractWe simulated light-scattering by small and wavelength-sized cubes with three largely different values of the refractive index using the discrete dipole approximation (DDA) and the T-matrix method. Our main goal was to push the accuracy of both methods to the limit. For the DDA we used an earlier developed extrapolation technique based on simulation results for different levels of discretization. For the T-matrix method we developed a procedure to estimate a confidence range for the simulated value, using results for different values of the truncation index (number of multipoles). In most cases this confidence range was reliable, enclosing the corresponding DDA result. We present benchmark results by both methods, including estimated uncertainties, for selected integral and angle-resolved scattering quantities. Estimated relative uncertainties of the DDA result are unprecedentedly small (from 10 −7 to 10 −3 ), while relative differences between the T-matrix and DDA results are larger (from 10 −4 to 0.2) in accordance with estimated T-matrix uncertainties.

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“…We use a numerical method ) which has been experimentally verified for porous particles (Hage, Greenberg and Wang 1990). The first step in these calculations is to build a model to represent the most important features of a porous aggregate.…”

Section: Quantitiesmentioning

confidence: 99%

The Dust in the Coma of Comet Halley

Hage

Greenberg

1991

International Astronomical Union Colloquium

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ABSTRACT. The interstellar dust model of comets is numerically worked out to satisfy several basic constraints provided by observations of comet Halley and to derive the porosity of coma dust. The observational constraints are: (1) the strengths of the 3.4 (J,m and 9.7 /jm emission bands; (2) the relative amount of silicates to organic materials; (3) the mass distribution of the dust. The results indicate that coma dust has a porosity in the range 0.93 < P < 0.975. Preliminary calculations concerning the observed linear polarization of comet Halley are presented. IntroductionThe purpose of this work is to provide evidence for the model of comets by Greenberg (1985) by showing that interpretation of ground based and spacecraft observations of the coma of comet Halley may be successfully performed on the basis of this model. We present here the main ideas of recent work (Greenberg and Hage 1990; see this paper for details) and some new, preliminary results concerning the interpretation of the observed linear polarization of light scattered by the coma of comet Halley.In terms of the present model, the dust in the coma consists of porous aggregates (figure la) consisting of interstellar core-mantle particles (figure lb). Comets are assumed to be aggregates of particles as shown in figure lc. The porosity, P, of the aggregates is defined as the relative amount of volume filled by vacuum inside the aggregate. The comet model predicts 0.6 < P < 0.83 for comet nuclei and 0.9 < P < 0.975 for coma dust. MethodBasically, we want to show that on the basis of the present comet model, it is possible to explain the observed strengths of the 3.4 fim (Danks et al. 1987) and 9.7 /xm (Hanner et al. 1987) emission bands of the coma of comet Halley, in terms of: (1) the mass ratio of silicates to organic materials as measured in situ (Kissel and Krueger 1987) and (2) the mass distributions of the dust, which were also measured in situ (McDonnell et al. 1989, Mazets et al. 1987. The shape of the 9.7 fim feature will not be considered here, although it may also be explained. The above is accomplished by going through the following scheme: (1) Assume the porosity of the coma dust is unknown and use it as a free parameter. (2) Calculate the thermal flux from the coma as a function of the dust porosity using: (a) the observed mass distributions; (b) the observed mass ratio in the dust of silicates:organics=2:l; (c) the interstellar dust model of comets to provide the morphology and specific chemical composition of the dust.The model calculations to determine the thermal emission of the coma dust particles with their complicated shapes, as a function of their porosity, size and distance to the sun are described fully in and in Greenberg and Hage (1990). (3) Equate, if possible, the calculated results with observed values, at the wavelengths of 9.7 and 3.4 /im. If the observed values are matched, then not only are spacecraft and ground based observations tied together, but a (representative mean) value for the dust porosity is also found...

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Scattering from arbitrarily shaped particles: theory and experiment

Cited by 56 publications

References 12 publications

The discrete dipole approximation: An overview and recent developments

The discrete dipole approximation: An overview and recent developments

Light scattering by a cube: Accuracy limits of the discrete dipole approximation and the T-matrix method

The Dust in the Coma of Comet Halley

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