A light scattering study of non equilibrium fluctuations in liquid mixtures to measure the Soret and mass diffusion coefficient

Fabrizio Croccolo (1, 2) , Henri Bataller (1) , F. Scheffold (2)

1 LFCR - Laboratoire des Fluides Complexes et leurs Réservoirs
2 Physics Department

We use dynamic near field scattering to measure the dynamics of concentration non equilibrium fluctuations at the steady-state of Soret separation. The analysis reveals that above a threshold wave vector q c, the dynamics is governed by diffusion while at smaller wave vectors, gravity dominates. From the measurements, we extract both the mass diffusion and the Soret coefficients. Comparing our results with literature data, we find good agreement confirming that the proposed experimental technique can be considered a sound approach for the study of thermodiffusion processes.

Mots clés: Experimental techniques; Liquid mixture; Literature data; Mass diffusion; Mass diffusion coefficients; Near-field scattering; Nonequilibrium fluctuations; Soret coefficients; Thermodiffusion; Threshold waves; Wave vector Engineering controlled terms: Dynamics Engineering main heading: Diffusion in solids

Fabrizio Croccolo, Henri Bataller, F. Scheffold. A light scattering study of non equilibrium fluctuations in liquid mixtures to measure the Soret and mass diffusion coefficient. Journal of Chemical Physics, 2012, 137 (23), pp.Article number234202. ⟨10.1063/1.4771872⟩. ⟨hal-00833880⟩