Phase change in adsorbed helium at low temperature

Several recent reports indicate a growing interest in the properties of adsorbed helium at low temperatures. This interest is based on the expected influence of restrictions of mobility and dimensions on thermodynamic properties such as heat capacity,(1,2) adsorption isotherms,(3) magnetic susceptibility,(4-6) and nuclear polarization.(7) This Letter presents specific heat data for adsorbed helium in the temperature range from 0.25 to 4°K, at several partial monolayer coverages. We interpret the results as indicating the existence of two surface phases. See Also: Erratum: D. L. Goodstein, J. G. Dash, and W. D. McCormick, Phase Change in Adsorbed Helium at Low Temperature., Phys. Rev. Lett. 15, 740 (1965).