RAYLEIGH-SCATTERING IN A LIQUID FAR FROM THERMAL-EQUILIBRIUM

We report the results of Rayleigh-scattering experiments in liquid toluene that is subjected to a stationary temperature gradient, but which otherwise is kept in a quiescent state. The measurements were made with temperature gradients up to 224 K/cm and scattering angles down to 0.45-degrees. They probe fluctuations with wavelengths up to 40-mu-m and demonstrate the presence of long-range fluctuations in a nonequilibrium liquid. The strength of the observed nonequilibrium heat-mode and viscous-mode fluctuations varies with the square of the temperature gradient and with the fourth power of the wavelength of the fluctuations, in agreement with the behavior predicted by fluctuating hydrodynamics.