CONTACT-ANGLE OF LIQUID-HE-4 ON A CS SURFACE

We have measured the contact angle Theta of He-4 on cesium-coated tung sten plates as a function of temperature. We find that Theta decreases to zero at T approximate to 2.0 K in agreement with the wetting tempe rature found on bulk Cs. At T = 0 K the contact angle is 48 degrees +/ - 1 degrees, significantly larger than the predicted value of approxim ately 30 degrees. The energy of the interface between Cs and liquid He -4 has a large temperature dependence. This suggests that there are lo w-lying excitations on the liquid helium surface at this interface. In deed it appears that liquid He-4 at this interface is similar to that at a free surface.