Nanooptics and photonics
Optical parameters of concentrated suspensions of graded nano-sized particles
Balika S.D, Sushko M.Ya.
Department of Theoretical Physics and Astronomy, Odesa I.I.Mechnikov National University. 2 Dvoryans’ka St., Odesa 65026, Ukraine. 
E-mail: svitlana.balika@onu.edu.ua

An accurate study of light scattering processes in strongly inhomogeneous random systems (colloids, suspensions, emulsions, etc.) and of related optical parameters (extinction mean-free-path length l, transport mean-free-path length l*, scattering anisotropy parameter g, etc.) suggests the use of the statistical theory of multiple scattering. However, even for relatively small volume concentrations c of optical inhomogeneities and differences ∆ε between the dielectric constants of the inhomogeneities and the host medium, the mathematical treatment becomes notoriously difficult [1]: one is challenged to deal with both (a) multiple scattering and many-particle correlation effects and (b) divergences in high-order terms in the iterative series. 
Our approach to the problem is based on the fact that for c ≥ 0.05 and visible light, the number of nano-sized scatterers per cubic wavelength considerably exceeds unity. From a physicist’s point of view, the scattering by such (“compact”) groups of scatterers is actually single. Using technique [2], we developed theory [3] to incorporate many-particle effects inside compact groups into single (in the indicated sense) scattering from concentrated dispersions with arbitrary ∆ε. 
In this report, we present further developments of theory [3] for suspensions of inhomogeneous nano-sized particles and discuss their feasible applications to the study of the properties of interfacial regions (say, the electric double layer) in the system. The efficiency of the theory is demonstrated by the comparison of its results for l, l*, and g with experimental data. 

1.	Kuzmin V. L. Contribution of multiple scattering to the dielectric constant of a randomly inhomogeneous medium // JETP.-2005.-100, N 5.-P. 1035-1041.
2.	Sushko M. Ya. Molecular light scattering of multiplicity 1.5 // JETP.-2004.-99, N 6.-P. 1183-1188.
3.	Sushko M. Ya. Compact group approach to analysis of the dielectric and optical characteristics of finely dispersed systems and liquids // J Phys Studies.-2009.-13, N 4.-P. 4708-1-5.