Heat capacity of quantum adsorbates: Hydrogen and helium on evaporated gold films
- Univ. of California, Berkeley, CA (United States). Dept. of Physics
The author has constructed an apparatus to make specific heat measurements of quantum gases adsorbed on metallic films at temperatures between 0.3 and 4 K. He has used this apparatus to study quench-condensed hydrogen films between 4 and 923 layers thick with J = 1 concentrations between 0.28 and 0.75 deposited on an evaporated gold surface. He has observed that the orientational ordering of the J = 1 molecules depends on the substrate temperature during deposition of the hydrogen film. He has inferred that the density of the films condensed at the lowest temperatures is 25% higher than in bulk H{sub 2} crystals and have observed that the structure of those films is affected by annealing at 3.4 K. The author has measured the J = 1 to J = 0 conversion rate to be comparable to that of the bulk for thick films; however, he found evidence that the gold surface catalyzes conversion in the first two to four layers. He has also used this apparatus to study films of {sup 4}He less than one layer thick adsorbed on an evaporated gold surface. He shows that the phase diagram of the system is similar to that for {sup 4}He/graphite although not as rich in structure, and the phase boundaries occur at different coverages and temperatures. At coverages below about half a layer and at sufficiently high temperatures, the {sup 4}He behaves like a two-dimensional noninteracting Bose gas. At lower temperatures and higher coverages, liquidlike and solidlike behavior is observed. The Appendix shows measurements of the far-infrared absorptivity of the high-{Tc} superconductor La{sub 1.87}Sr{sub 0.13}CuO{sub 4}.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 286267
- Report Number(s):
- LBNL-38980; ON: DE96013825; TRN: 96:023271
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: Jun 1996
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
QUANTUM FLUIDS
SPECIFIC HEAT
HYDROGEN
ADSORPTION
HELIUM 4
LANTHANUM OXIDES
ABSORPTIVITY
STRONTIUM OXIDES
COPPER OXIDES
GOLD
SORPTIVE PROPERTIES
TEMPERATURE RANGE 0000-0013 K
THICKNESS
TEMPERATURE DEPENDENCE
BOSE-EINSTEIN GAS
HIGH-TC SUPERCONDUCTORS
EXPERIMENTAL DATA
MICROBALANCES
CALORIMETERS
PHASE TRANSFORMATIONS
ORDER PARAMETERS
CRYOGENICS
CRYSTAL STRUCTURE