Nanoscale physics

  Short-scale scattering effects in critical fluids and heterogeneous media 
Sushko M.Ya, Krychun T.V., Vorobel A.V.
Department of Theoretical Physics and Astronomy, Odesa I.I.Mechnikov National University. 2 Dvoryans’ka St., Odesa 65026, Ukraine. 
E-mail: mrs@onu.edu.ua 

     Multiple scattering theory is a traditional technique for study of optical properties of systems incorporating various local inhomogeneities, such as order-parameter fluctuations in critical fluids, dispersed particles in solutions, or filler inclusions in composite materials. Since, in most cases, the higher-order correlation functions of a system are unknown, the pertinent iterative series for the scattered field is truncated to include several corrections to the first Born approximation, and the higher correlation functions involved are replaced by model expressions. 
     We argue that such an approach leads to overlooking significant effects caused by multiple reemissions and correlations among inhomogeneities spaced by distances much shorter than the wavelengths of probing radiation in the system. Using a special representation fot the inner propagators, these “short-scale” scattering contributions can be singled out from the entire iterative series and then summed up without employing uncontrolled assumptions.  
     To exemplify one of these effects, we present our latest results of processing critical opalescence data for xenon [1]. They reveal the significance of so-called molecular light scattering of multiplicity 1.5 [2] near the liquid-vapor critical point. In particular, this scattering may noticeably affect the width of the overall spectra, causing its multiplicative renormalization and altering its temperature dependence. 
     The other example demonstrates the effect of short-scale scatterings on the parameters of photon transport in concentrated suspensions of nanoparticles [3].

1.	Trappeniers N.J. et al. Investigation of multiple scattering contributions to the depolarization of light scattered by carbon dioxide and xenon in the critical region. I. Basic theoretical formulae and experimental data // Physica.-1980.-101A,-P. 431-458.
2.	Sushko M. Ya. Experimental observation of triple correlations in fluids // Condens. Matter Phys.-2013.-16.-P. 13003-1-12.
3.	Sushko M. Ya. Compact group approach to the analysis of dielectric and optical characteristics of finely dispersed system and liquids // J. Phys. Studies.-2009.-13.-P. 4708-1-5.