Adsorption of 4He on spheron and grafoil between 2 and 30 K

Abstract

Measurements of heat capacities at low temperatures of ⁴He adsorbed on Spheron (2–15 K) and on Grafoil (8–30 K) show a contribution below 10 K from defects in the substrate and the presence of a broad phase transition in the adsorbed film at higher temperatures. The high energy of this transition (> 312 J mol^–1) suggests that this transition is from two-dimensional solid to two-dimensional gas. Heats of adsorption and heat capacities of adsorbed ⁴He reveal differences in the structures of the Spheron and Grafoil substrates.