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 $\ensuremath{\xi}$ and the shear viscosity, a parameter-free fit is obtained with theory in the region $55>k\ensuremath{\xi}>0.32$. The renormalization-group-modified mode theory is shown to be necessary; however, we find a value of the dynamical exponent $z=2.992\ifmmode\pm\else\textpm\fi{}0.014$ instead of 3.065.