Surface effects of He-4 coating on the viscosity and the slip length of normal and superfluid He-3

We have measured the viscosity, eta, and the slip length, zeta, of normal a nd superfluid He-3 using a torsional oscillator with a thick sample space. We coated the oscillating surface with 2.5 layers of He-4 film to study how the He-4 thin film changes the scattering mechanism of He-3 quasiparticles at the cell wall at 5 bar and 21 bar. In the normal phase, the temperature dependence of the viscosity was changed a little by the He-4 film at 21 ba r but no change was observed at 5 bar. The slip length was enhanced by He-4 coating at 5 bar. This enhancement indicates the increase of specularity o f He-3 quasiparticles scattering at the oscillating surface. On the other h and, a reduction of the slip length was observed at 21 bar. In the superflu id phase, the temperature dependence of zeta supports the existence of Andr eev reflection even with He-4 film on the surface at 5 bar and 21 bar.