Transport Properties of GaseousHe3andHe4

A complete quantum phase-shift calculation of several transport coefficients of gaseous ${\mathrm{He}}^3$, ${\mathrm{He}}^4$, and ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures has been carried out from 0.2 to 300°K for a Lennard-Jones (12-6) potential model. Emphasis was placed on those properties for which new experimental data had become available, which included the viscosity of ${\mathrm{He}}^4$, the thermal conductivity of ${\mathrm{He}}^3$ and ${\mathrm{He}}^4$, the spin diffusion of ${\mathrm{He}}^3$, and ordinary diffusion and thermal diffusion of ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures. Agreement was in general suprisingly good for a potential as simple as this. A rather more elaborate potential may be required to obtain agreement over the full range of experimental measurements of transport properties and equation-of-state properties of the helium isotopes, which extends from less than 1°K to over 1000°K.