Light Scattering by Agglomerates: Coupled Electric and Magnetic Dipole Method

Mulholland, George W.; Bohren, Craig F.; Fuller, Kirk A.

doi:10.1021/la00020a009

Cited by 203 publications

(155 citation statements)

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“…Even so, previous studies showed that RDG in general produces reasonably accurate results for the scattering properties of soot (Dobbins and Megaridis 1991;Farias et al 1996). Multiple scattering within a fractal aggregate was found small in several studies (Berry and Percival 1986;Singham and Bohren 1993;Mulholland et al 1994;Farias et al 1996).…”

Section: Rayleigh-debye-gans Fractal Aggregate Theorymentioning

confidence: 95%

Investigation of Absorption and Scattering Properties of Soot Aggregates of Different Fractal Dimension at 532 nm Using RDG and GMM

Liu¹,

Wong

Snelling³

et al. 2013

Aerosol Science and Technology

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Radiative properties of numerically generated fractal soot aggregates of different fractal dimensions were studied using the numerically accurate generalized Mie-solution method (GMM) and the Rayleigh-Debye-Gans (RDG) approximate theory. Fractal aggregates of identical prefactor but different fractal dimensions, namely, 1.4, 1.78, and 2.1, were generated numerically using a tunable algorithm of cluster-cluster aggregation for aggregates containing up to 800 primary particles. Radiative properties of these aggregates were calculated at a wavelength of 532 nm assuming a soot refractive index of 1.6 + 0.6i. Four commonly used structure factors in the RDG approximation were used to investigate the effect of structure factor on the differential and total scattering cross-sections and the asymmetry factor. The differential and total scattering properties calculated using the RDG approximation become increasingly sensitive to the structure factor with increasing the fractal dimension. Primary particle interactions are the fundamental mechanism for the aggregate absorption enhancement for small aggregates and the shielding effect for larger aggregates. The extent of these two competing factors is dependent on the fractal dimension and aggregate size. RDG reasonably predicts the effect of fractal dimension on the scattering properties, but fails to account for the effect of aggregation or fractal morphology on the absorption property of fractal soot aggregates, though the error is in general less than 15%.

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Section: Rayleigh-debye-gans Fractal Aggregate Theorymentioning

confidence: 95%

Investigation of Absorption and Scattering Properties of Soot Aggregates of Different Fractal Dimension at 532 nm Using RDG and GMM

Liu¹,

Wong

Snelling³

et al. 2013

Aerosol Science and Technology

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“…Soot carbon is composed of primary spherules with radii R p 0.025 µm that are aggregated with other spherules into large particles, and the resulting agglomerates look like chains of spheres with multiple branches (hence the term "chain aggregates;" Li et al, 2003a, b;Wentzel et al, 2003;Chakrabarty et al, 2006;Adachi et al, 2010;Wu et al, 2012;Chakrabarty et al, 2013). The absorption cross section for the aggregated particles can be reasonably modeled as a collection of the primary sC spheres, even though the agglomerates have complex shapes (Mulholland et al, 1994;Fuller, 1995;Farias et al, 1996;Fuller et al, 1999;Sorensen, 2001;Schnaiter et al, 2003;Chakrabarty et al, 2007;Liu et al, 2008;Chung et al, 2012a). Thus, the primary spherule size is the appropriate length scale for determining AAE (Bergstrom et al, 2002), and externally mixed sC aggregates occupy the parameter space highlighted by the maroon rectangle in the upper left of Fig.…”

Section: Aae For Spectrally Invariant Kmentioning

confidence: 99%

Remote sensing of soot carbon – Part 2: Understanding the absorption Ångström exponent

et al. 2016

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Abstract. Recently, some authors have suggested that the absorption Ångström exponent (AAE) can be used to deduce the component aerosol absorption optical depths (AAODs) of carbonaceous aerosols in the AERONET database. This AAE approach presumes that AAE 1 for soot carbon, which contrasts the traditional small particle limit of AAE = 1 for soot carbon. Thus, we provide an overview of the AERONET retrieval, and we investigate how the microphysics of carbonaceous aerosols can be interpreted in the AERONET AAE product. We find that AAE 1 in the AERONET database requires large coarse mode fractions and/or imaginary refractive indices that increase with wavelength. Neither of these characteristics are consistent with the current definition of soot carbon, so we explore other possibilities for the cause of AAE 1. AAE is related to particle size, and coarse mode particles have a smaller AAE than fine mode particles for a given aerosol mixture of species. We also note that the mineral goethite has an imaginary refractive index that increases with wavelength, is very common in dust regions, and can easily contribute to AAE 1. We find that AAE 1 can not be caused by soot carbon, unless soot carbon has an imaginary refractive index that increases with wavelength throughout the visible and near-infrared spectrums. Finally, AAE is not a robust parameter for separating carbonaceous absorption from dust aerosol absorption in the AERONET database.

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“…When the feature size of the high refractive index dielectric nanoparticles is significantly smaller than the incident wavelength, the resulting optical resonance can be described by the effective electric dipole and magnetic dipole as [32]:…”

Section: Theoretical Modal Of Coupled Nanoparticlesmentioning

confidence: 99%

“…When considering the interaction between multiple nanoparticles, the electric and magnetic fields at the ith particle, as caused by the jth particle, can be represented by [32] …”

Section: Theoretical Modal Of Coupled Nanoparticlesmentioning

confidence: 99%

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Broadband Electromagnetic Dipole Resonance by the Coupling Effect of Multiple Dielectric Nanocylinders

Fang

Jing

et al. 2018

Applied Sciences

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Broadband resonant scattering in a visible region that can be obtained by coupled multiple silicon nanocylinders. For a single high refractive index silicon nanocylinder, the electric dipole and magnetic dipole resonances can be observed. By constructing a silicon nanocylinder dimer, the interaction between the particles plays an important role in broadband scattering. Interestingly, due to magnetic-magnetic dipole interaction, a splitting phenomenon of magnetic resonance mode is revealed. A new magnetic resonant mode emerges at a longer wavelength in dimer and trimer by changing the diameter of one nanocylinder in dimer or trimer, and the gap size between nanocylinders. The scattering bandwidth can further increase with the effect of substrate, which is attributed to the extension of resonant mode into substrate. The broadband optical response can be revealed by the calculated scattering resonant spectra and the spatial electromagnetic field distributions. Furthermore, the transmission of periodic nanocylinder structure, including single nanocylinder and dimer, is demonstrated. By decreasing the gap between nanocylinders in dimer for periodic array structure, a new electric resonant mode occurs. These results can provide a guideline to realize broadband resonant optical elements.

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Light Scattering by Agglomerates: Coupled Electric and Magnetic Dipole Method

Cited by 203 publications

References 0 publications

Investigation of Absorption and Scattering Properties of Soot Aggregates of Different Fractal Dimension at 532 nm Using RDG and GMM

Investigation of Absorption and Scattering Properties of Soot Aggregates of Different Fractal Dimension at 532 nm Using RDG and GMM

Remote sensing of soot carbon – Part 2: Understanding the absorption Ångström exponent

Broadband Electromagnetic Dipole Resonance by the Coupling Effect of Multiple Dielectric Nanocylinders

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