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Equilibrium Properties of Submonolayer He^4 Films


Wallace, John Longstreet (1971) Equilibrium Properties of Submonolayer He^4 Films. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/A99W-KR64.


Isosteres have been measured for submonolayer films of helium-four adsorbed on a sintered copper sponge precoated with each of the other noble gases, These measurements were carried out at temperatures between 3°K and 4°K, and at coverages between 0.5 and 1.0 monolayer; the pressures encountered were in the range from 10-7 Torr to 10-1 Torr. On the neon-coated substrate, the lower binding energy and higher lateral mobility made it feasible to take useful data at coverages as low as 0.025 monolayer. From the isosteres, information is derived about the partial molar entropy, entropy and heat capacity of the film.

It appears that the submonolayer film is a well-defined entity whose qualitative properties remain unchanged as the substrate precoating is varied, These include a transition into a highly ordered state as the coverage is increased, a total heat capacity which is not monotonic with coverage, and significant lateral mobility. The transition into the ordered state is initiated at higher coverage as the temperature is lowered, and this anomaly is discussed in terms of a model in which two dimensional crystalline patches are broken up by thermal fluctuations.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Goodstein, David L.
Thesis Committee:
  • Unknown, Unknown
Defense Date:17 August 1970
Funding AgencyGrant Number
Record Number:CaltechTHESIS:06262017-102857880
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10342
Deposited By: Benjamin Perez
Deposited On:27 Jun 2017 16:01
Last Modified:21 Dec 2019 01:30

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