Abstract
We report results of experiments in which pulses of helium vapor with translational energies of 3 K are directed at a thin film of superfluid helium at a temperature of about 0.2 K suspended over a cesium covered orifice in a platinum film. The response of the superfluid film was detected by a super-conducting titanium bolometer placed on the side of the film opposite to that of the source. For films of approximately 1 mm in thickness we find no response of the bolometer within the limits of our detector. However, for films of less than 100 μ thickness, we find a response which is of the same temporal shape, but smaller in amplitude, than that of the orifice when it is not covered with superfluid helium. We interpret these results to mean that we are seeing phonon mediated transmission in the thin films. Roton and condensate mediated transmission amplitudes for these conditions are apparently too small for us to detect in any of the films. This result is consistent with the theoretical results of Sobnack and Inkson [M. B. Sobnack, J. C. Inkson, and J. C. H. Fung, Phys. Rev. B 60, 3465 (1999)] concerning the amplitude of roton to atom and photon to atom conversion as a function of the atomic energy.
Original language | English (US) |
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Pages (from-to) | 429-449 |
Number of pages | 21 |
Journal | Journal of Low Temperature Physics |
Volume | 140 |
Issue number | 5-6 |
DOIs | |
State | Published - Sep 2005 |
Bibliographical note
Funding Information:This work was supported by two NASA GSRP awards, by NSF grant NSP/DMR 9980329, and by the Physics Department, the Graduate School, the Institute of Technology, and the Supercomputing Institute of the University of Minnesota, William Zimmermann is thanked for sharing facilities in the laboratory and for numerous discussions and we thank Matt Fritts for redrawing Fig. 2.
Keywords
- Phonons
- Superfluid
- Suspension
- Transmission