Rayleigh Linewidth in Xenon Near the Critical Point

The Rayleigh linewidth Γ of xenon was measured on the critical isochore between 0.003 and 5.0^∘{}C above Tc. In the hydrodynamic region (qξ<~0.2) we find Γ=q²χ₀[(T-Tc)Tc]^γ-ψ with χ₀=(6.94±0.21)×10^-4 cm²/sec, and γ-ψ=0.751±0.004. Our data over the entire region 0.009<~qξ<~6.7 agree quite well with the recent Kawasaki extended mode-mode coupling theory. However, the Kadanoff-Swift-Kawasaki result γ-ψ=ν does not appear to be valid.