Local field and electromagnetic properties of disordered systems.
Item
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Title
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Local field and electromagnetic properties of disordered systems.
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Identifier
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AAI9009721
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identifier
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9009721
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Creator
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Chen, Zhe.
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Contributor
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Adviser: Ping Sheng
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Date
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1989
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Optics | Physics, General
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Abstract
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This thesis regards the investigation of the static and dynamic electromagnetic properties of random systems. In the static limit, a generalized Onsager's approach is developed for the study of local field distribution and its implications for the dielectric properties in random systems. Correlation with the microstructure of random materials is highlighted. We find the distribution of local fields to display a double-peak character in general. This unexpected behavior is explained in terms of two types of local environments defined relative to the applied field. The quantitative characteristics of the distribution are found to be sensitive to the microstructure of a random system. In particular, the standard deviation of the distribution is directly proportional to the product of the polarizability and a parameter that measures the local anisotropy of the medium. The mean of the distribution, on the other hand, is found to be bounded below by the Lorentz local field value, with the fractional deviation from the lower bound proportional to the variance. The later quantity is also identified as the correction factor to the Clausius-Mossotti relation, and the extended spatial correlation is demonstrated to have a significant effect on this factor.;In the dynamic limit, we study the optical properties of colloidal gold aggregates where the focus is on the effects of multiple scattering on the structure factor {dollar}S(q){dollar} and the consequences of high-order multiple interaction on the absorption and depolarized scattering by the colloidal aggregates. Effects of multiple scattering on the structure factor are examined by relating them to the spatial correlations of the local fields. It is found that the multiple scattering affects only the magnitude of {dollar}S(q){dollar} but not its {dollar}q{dollar}-dependence for {dollar}q{dollar} {dollar}\leq{dollar} {dollar}a\sp{lcub}-1{rcub}{dollar}, where {dollar}a{dollar} is on the order of a single particle size. This makes light scattering a viable technique for structure determination. The high-multipole interaction and its implications on the absorption and depolarized scattering characteristics are examined through a rigorous scattering solution of a simple model that consists of a periodic chain of cylindrical particles. Results obtained are in good accord with experimental observations.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
