Transport properties of helium near the liquid-vapor critical point. III. Thermal diffusion ratio, conductivity, and relaxation times of3He-4He mixtures

Thermodiffusion in the Critical Region

“…In this case, the asymptotic power laws do not describe the experimental data. Instead, the experimental values for the thermal diffusion ratio k T seem to diverge with an exponent of 1.23 [51], almost twice as high as the asymptotic prediction of 0.67. Until recently, the situation was similar for the thermal conductivity λ T near plait points.…”

“…Until recently, the situation was similar for the thermal conductivity λ T near plait points. Experiments [51,52] suggested a pure-fluid like divergence of λ T near a plait point, in contrast to the asymptotic prediction for mixtures that λ T approach a finite value at the critical point, cf. Eq.…”

“…Also shown are the asymptotic power laws of Eqs. [50,51], the lines represent the asymptotic power laws crossover thermal diffusion ratio increases much more rapidly than predicted from the asymptotic analysis for temperatures not too close to the critical point. For very small reduced temperatures, the crossover prediction [25] approaches the asymptotic power law (38), suggesting that the asymptotic critical region is extremely small and does not cover the temperature range, where experiments were performed on …”

“…Note that, as predicted by dynamic RG, the experimental values for k T D remain constant throughout the critical region. Thermodiffusion near plait points was investigated for mixtures of 4 He-3 He by Horst Meyer and co-workers [50,51]. In Fig.…”

“…In Fig. 3 we present thermal diffusion data [50,51] in the critical region of a 4 He-3 He mixture with mole-fraction x( 3 He) = 0.8. Also included in the figure are the asymptotic predictions of Eqs.…”