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Small-angle Rayleigh scattering from nonequilibrium fluctuations in liquids and liquid mixtures

1994; Elsevier BV; Volume: 204; Issue: 1-4 Linguagem: Inglês

10.1016/0378-4371(94)90440-5

1873-2119

W. B. Li, P. N. Segrè, Robert W. Gammon, J. V. Sengers,

Advanced Thermodynamics and Statistical Mechanics

We have developed an improved experimental arrangement for measuring small-angle Rayleigh scattering in liquid systems subjected to a stationary temperature gradient. This improved arrangement has enabled us to measure nonequilibrium fluctuations with a simple helium-neon laser. We have used this technique to measure long-range nonequilibrium fluctuations in n-hexane and in several mixtures of n-hexane with toluene, thus complementing measurements for the equimolar mixture obtained previously. The experiments confirm that all diffusive nonequilibrium fluctuations vary with (▿T)2/k4, where ▿T is the imposed temperature gradient and where k is the wave number of the fluctuations. A quantitative comparison of the strength of these nonequilibrium fluctuations with the theoretical predictions is also presented.