Thermal Diffusion Measurements near the Liquid-Vapor Critical Point

The authors report measurements of the density and temperature gradients in ³He-⁴He mixtures near their liquid-vapor critical point, as induced by a heat flux. From these they deduce the thermal diffusion ratio kT and the conductivity κ. They find that kT and κ diverge with respective effective exponents φ≈1.2 and ψ≈0.6. Both of these results are in contradiction with the asymptotic predictions for binary mixtures and are discussed in the light of the hydrodynamic transport equations.