NIST Time|NIST Home|About NIST|Contact NIST

HomeAll Years:AuthorKeywordTitle2005-2010:AuthorKeywordTitle

Light Scattering by Agglomerates: Coupled Electric and Magnetic Dipole Method.

pdf icon Light Scattering by Agglomerates: Coupled Electric and Magnetic Dipole Method. (1215 K)
Mulholland, G. W.; Bohren, C. F.; Fuller, K. A.

Langmuir, Vol. 10, No. 8, 2533-2546, 1994.


National Aeronautics and Space Administration, Washington, DC


light scattering; agglomerates; Rayleigh-Debye light scattering; sphere sizes


The coupled electric dipole method (CED) for treating light scattering by an agglomerate particle is extended to include both the electric and magnetic dipole terms (CEMD). The accuracy of these two methods along with the Rayleigh-Debye (RD) method is obtained by comparing with the exact solution for two spheres in contact. It is found that the additional term extends the range of the coupled dipole method from a primary sphere diameter of about 0.06 mm to about 0.12 mm for soot-like particles at visible wavelengths. The scattering and extinction cross sections, the differential scattering, and the polarization ratio are computed for agglomerates with 17, 52, and 165 primary spheres for soot-like and silica-like agglomerates. The agglomerates are generated by Brownian dynamics computer simulation of in-flame growth. A comparison is made among RD, CED, and CEMD. The effects of primary sphere diameter and agglomerate size on the validity of the RD approximation is discussed. It is shown that the polarization ratio computed by CEMD is sensitive to the primary sphere size independent of agglomerate size.