dynamic light scattering abbr., DLS; PCS; QELS; DLLS otherwise Dynamic Laser Light Scattering; Photon Correlation Spectroscopy; Quasi-Elastic Light Scattering (rus. спектроскопия, фотонная корреляционная otherwise динамического рассеяния света, метод; квазиупругое рассеяние света; неупругое светорассеяние; динамическое светорассеяние; лазерная корреляционная спектроскопия abbr., ДРС; ЛКС) — A method to study structure and dynamics of gas and liquid media basing on analysis of temporal autocorrelation function of radiation scattering intensity.

Description

The temporal autocorrelation function of scattering intensity determines characteristic time scales on which motion of scattering centres is correlated i.e. depends on their position in preceding moments of time. Thus, the autocorrelation function of light scattered by a colloidal solution of particles uniform in size decreases exponentially with time. Judging by the decay rate we can determine particles' self-diffusion coefficient and then, by Stokes' and Einstein's formulae, calculate their hydrodynamic radius. If the solution contains particles of different sizes we can calculate the histogram of particle size distribution using various mathematical algorithms.

To observe temporal correlations of scattered radiation the researcher should use laser radiation which is coherent and monochromatic. The size of the studied objects should be comparable to the light wavelength; for smaller particles incident light is scattered evenly in all directions. The use of an X-ray radiation source with a very small wavelength enables the study of molecular-scale structures.

The photon correlation spectroscopy method is used to study the behaviour of various colloidal systems as well as polymer solutions and gels. In recent years, this method has found application in analysis of body fluids in medical diagnostics.

Authors

  • Khokhlov Alexey R.
  • Govorun Elena N.

Sources

  1. Dynamic Light Scattering // Wikipedia, the free Encyclopedia. — http://en.wikipedia.org/wiki/Dynamic_light_scattering (reference date: 01.08.2010).
  2. Wyatt Technology corporation Understanding QELS (Dynamic Light Scattering). —www.wyatt.com/theory/qels/ (reference date: 01.08.2010).

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