2026-09-22T17:11:15Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/22107 2023-07-10 col_2142_5131 col_2142_8859 com_2142_5130 com_2142_8858 com_2142_234

Mochel, J.M. Shirron, Peter John 2011-05-07T13:29:10Z 2011-05-07T13:29:10Z 10000-01-01 1989 High-precision measurements of third sound velocities in atomically thin $\sp4$He films on Ar, Ne, CO$\sb2$, and H$\sb2$ substrates in the T = OK limit reveal a periodic structure not corresponding to whole layers. We analyze the data in two extreme limits. First, treating the helium film as an incompressible, continuous fluid, the data indicate that the chemical potential has a contribution proportional to $\ell\sp{-6}$, where $\ell$ is a layer coverage, which is modulated at intervals of.62 $\pm$.04 layers, and which weakens the van der Waals potential. Second, if we assume the potential is exactly the van der Waals potential, the data indicate the existence in the film of a damped smectic density wave with a periodicity of.54 $\pm$.04 layers, independent of substrate. The correct description of He films must lie between these extremes. We find the inert layer coverages to be 1 full layer on Ar, Ne, and CO$\sb2$, and.36 layers on H$\sb2$. Coverages scales were determined using helium adsorption isotherms. A self-consistent analysis method was developed based on the modified Brunauer-Emmet-Teller method for low coverages and the Fenkel-Halsey-Hill vapor pressure relation at high coverages. The analysis establishes the layer capacities for helium films and helium-substrate chemical potential constants, $\Gamma$. Made available in DSpace on 2011-05-07T13:29:10Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9011023.pdf: 5493040 bytes, checksum: 4a7094e755d313d74d3e4e857e23a68a (MD5) Previous issue date: 1989 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:55:22Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:25:48-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9011023 (UMI)AAI9011023 http://hdl.handle.net/2142/22107 eng Copyright 1989 Shirron, Peter John Physics, Condensed Matter Measurement of the chemical potential of thin helium films text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.