Thermal Diffusion in a Loaded Sphere—Smooth Sphere Mixture: A Model for 4He–HT and 3He–HD

The kinetic theory of a mixture of loaded spheres and smooth spheres of equal mass is developed as a model for thermal diffusion in the systems 3He–HD, 4He–HT, and 4He—D2. The inelastic effects in the loaded-sphere collisions are sufficient to explain the experimental ``anomalies'' observed in thermal diffusion involving the asymmetric hydrogen isotopes. The effects of spin polarization, though not dominant, are not negligible.