We have performed small-angle Rayleigh scattering measurements in toluene removed far from equilibrium by a large stabilizing temperature gradient. The experiments demonstrate the existence of long-range density correlations through a strong enhancement of the thermal fluctuations and they also reveal a negative contribution at shorter-time scales from the viscous fluctuations in agreement with the theoretical predictions. The experiments confirm that both effects vary with (delta T)2/q4. where delta T is the temperature gradient and q the wave number of the fluctuations.
Law, B.M., Gammon, R.W., Sengers, J.V., Dynamic Light Scattering from Long-Range Density Correlations in a Nonequilibrium Liquid, pp.147-152, Institute for Physical Science & Technology, University of Maryland, College Park, MD 20742.