TRANSITION-TEMPERATURES, ENTROPIES, INTERNAL ENERGIES, AND HEATS OF DESORPTION OF HE-4 FILMS ADSORBED ON GRAPHITE FROM VAPOR-PRESSURE MEASUREMENTS

Vapor pressure measurements of 4He adsorbed on Grafoil for coverages x = 0.94 and 1.00 were made as a function of temperature in the temperature range of 5-10 K. The data are presented as plots of ln p vs. 1/T and from these dp/dT vs. T curves are presented. For both coverages there is an indication of a phase transition, which agrees with the conclusions from specific heat data on the same system obtained by other authors. Molar entropies and internal energies, as well as isosteric heats of adsorption, were obtained as a function of coverage, and from the data the contribution to the total specific heat of the adsorbed films due to desorption was found to be considerable. © 1979 Plenum Publishing Corporation.