Rayleigh-Linewidth Measurements near the Critical Point of a Binary Fluid

Abstract

We report careful measurements of the Rayleigh linewidth of light scattered from a critical binary fluid. Laser heating and multiple-scattering effects are accounted for. With use of independent data for $\xi$ and the shear viscosity, a parameter-free fit is obtained with theory in the region $55>k\xi >0.32\mathrm{}$. The renormalization-group-modified mode theory is shown to be necessary; however, we find a value of the dynamical exponent $z=2.992\mathrm{}\pm 0.014$ instead of 3.065.