Heat capacity study of {sup 4}He desorbing from H{sub 2}-plated graphite

Journal Article · Sat Jul 01 04:00:00 EDT 1995 · Journal of Low Temperature Physics

DOI:https://doi.org/10.1007/BF00753840· OSTI ID:207135

Ebey, P S; Liu, Y M; Vilches, O E ^[1]

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1. Univ. of Washington, Seattle, WA (United States)

The authors report measurements of the surface binding energy of {sup 4}He adsorbed on 1.45, 2.15, or 3.15 layers of hydrogen plating graphite. The heat capacity of partial monolayer coverages of helium was measured using adiabatic heat pulse calorimetry from 0.2 to 9 K. Desorption of low surface density {sup 4}He films was indicated above {approximately}2 K by a broad peak in the heat capacity. A model was developed to calculate the specific heat of an ideal gas in two dimensions as it desorbs into an ideal gas in three dimensions. This model was used to obtain the binding energies from experimental data. The binding energies per atom are {minus}39, {minus}25.8, and {minus}22{+-}0.5K, respectively, for the three hydrogen platings. The 2-d compressibility of the partial solid second layer of H{sub 2} in the 1.45 layer H{sub 2} coverage was calculated from an increase in its melting temperature with increase of {sup 4}He 2-d pressure.

• Sponsoring Organization: USDOE
• OSTI ID: 207135
• Journal Information: Journal of Low Temperature Physics, Journal Name: Journal of Low Temperature Physics Journal Issue: 1-2 Vol. 100; ISSN JLTPAC; ISSN 0022-2291
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ADSORPTION
BINDING ENERGY
GRAPHITE
HELIUM 4
HYDROGEN
SPECIFIC HEAT
TEMPERATURE RANGE 0000-0013 K