Heat capacity of quantum adsorbates: Hydrogen and helium on evaporated gold films

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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 ... continued below

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159 p.

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Birmingham, J.T. June 1, 1996.

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  • Birmingham, J.T. Lawrence Berkeley National Lab., CA (United States). Materials Sciences Div.

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Description

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}.

Physical Description

159 p.

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INIS; OSTI as DE96013825

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  • Other Information: TH: Thesis (Ph.D.)

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  • Other: DE96013825
  • Report No.: LBNL--38980
  • Grant Number: AC03-76SF00098
  • DOI: 10.2172/286267 | External Link
  • Office of Scientific & Technical Information Report Number: 286267
  • Archival Resource Key: ark:/67531/metadc670458

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Creation Date

  • June 1, 1996

Added to The UNT Digital Library

  • June 29, 2015, 9:42 p.m.

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  • April 5, 2016, 11:40 a.m.

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Birmingham, J.T. Heat capacity of quantum adsorbates: Hydrogen and helium on evaporated gold films, report, June 1, 1996; California. (digital.library.unt.edu/ark:/67531/metadc670458/: accessed October 18, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.