Eur. Phys. J. E (2009) 29: 149-155
https://doi.org/10.1140/epje/i2009-10462-2

Regular Article

Multispeckle diffusing wave spectroscopy of colloidal particles suspended in a random packing of glass spheres

¹ Centre de Recherche Paul Pascal, CNRS UPR 8641, Université Bordeaux 1, 115 Avenue Schweitzer, F-33600, Pessac, France
² Institut de Physique de Rennes, UMR UR1-CNRS 6251, Université de Rennes 1, Campus de Beaulieu, F-35042, Rennes Cedex, France

^* e-mail: snabre@crpp-bordeaux.cnrs.fr
^** e-mail: jerome.crassous@univ-rennes1.fr

Received: 14 November 2008
Revised: 6 February 2009
Accepted: 10 April 2009
Published online: 12 June 2009

Abstract

We use a multispeckle diffusing wave spectroscopy (MSDWS) method to study the ensemble-averaged dynamics of the fluctuating speckle pattern when illuminating colloidal particles suspended in a static and opaque porous medium with a coherent light source. Experiments were performed with Brownian latex particles in a random packing of glass spheres. The mixing of the light scattered by the moving colloidal particles and the porous matrix gives rise to a plateau value of the intensity autocorrelation function in the long-waiting-time limit. From the plateau in the correlation function, we can determine the fraction of light scattered from moving particles and estimate the photon mean free path in the colloidal solution. The method opens up promising possibilities to probe the static fraction in semisolid materials.