ISSN:
1573-7357
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract We report on new measurements of the spontaneous decay threshold energyE c for high-frequency phonon propagation in He II at saturated vapor pressure atT=0.1 K. Superconducting tin tunnel generators and aluminum tunnel detectors were used in this study. The measurements show that the mean free path becomes much larger than the propagation length of 1.1 mm for a value ofE c =9.8±0.15 K. This agrees with the value originally reported (E c =9.5±0.4 K) by Dynes and Narayanamurti using aluminum tunnel generators, but is shown to correspond to the point where the phase velocity equals the sound velocity, when the phonons become stable, as first proposed by Pitayevski and Levinson. Evidence forn-phonon decay at energies lower thanE c is presented forn≳2 with a short mean free path (〈0.3 mm) at the two-phonon decay energy. The measured values of the dispersion parameters are shown to agree closely with the spline fit to neutron data due to Donnelly, Donnelly, and Hills.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00681516
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