THE HEAT-CAPACITY OF HE-4 MONOLAYERS ADSORBED ON EVAPORATED GOLD

The specific heat of He-4 condensed on an evaporated gold surface has been measured for coverages between 0.007 and 0.096 Angstrom(-2) and t emperatures between 0.4 and 3.0 K. There are at least two types of phy sisorption site on the gold surface with binding energies -83+/-7 and -94+/-7 K. For coverages below 0.06 Angstrom(-2) (similar to 0.5 monol ayers), the He-4 is a two-dimensional classical gas at sufficiently hi gh temperatures. At lower temperatures and higher coverages, the 4He f orms condensed phases, including liquids, solids commensurate with the gold lattice, and incommensurate solids. The phase diagram of He-4/ev aporated gold is similar to that for He-4/graphite, but the phase boun daries are shifted and not well defined, nor is the diagram as rich in structure.