Slip and the effect ofHe4at thesilicon3interface

We present measurements of the slip of normal ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ contained between a pair of highly polished silicon plates mounted on a torsional oscillator. The resulting effective viscosity of pure normal ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is not consistent with simple slip theory and shows characteristics previously observed only with a surface layer of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ present. We have also observed the onset of specularity induced by the addition of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. This onset occurs after 2 monolayers of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ have been completed and can be associated with superfluidity of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$.