A. F. Sinyuk and S. L. Oshchepkov
Stepanov Institute of Physics, Belarussian Academy of Sciences, pr. F. Skoriny, Minsk, 220072 Belarus
Received April 19, 1996
Abstract—The possibility of the estimation of the distribution of ultradisperse metal particles over the sizes
from spectral measurements of the coefficient of extinction in a visible range of spectrum was investigated. The
unambiguous solution of the relevant inverse problem is related to the presence of a clearly pronounced size
effect, which may be described in terms of classical electrodynamics by the dependence of the complex refrac-
tion index of an ultradisperse metal particle on their sizes. It was shown that from the viewpoint of information
validity of optical measurements, this effect results in a decreased sensitivity correlation of spectral values of
light extinction to particles of various sizes and makes it possible to adequately recover their size distribution.
The analysis was performed within the framework of numerical experiments. To solve the direct problem of
light scattering, the theory of diffraction of electromagnetic waves on uniform spherical particles was
employed; for the description of the size effect, the widely known model of the limited free path of conduction
electrons was used. Ultradisperse silver particles in gelatin were used as an example in this study. Highly dis-
perse dielectric particles of hematite and carbon black were considered as alternative objects that do not exhibit
an appreciable size effect.
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