Sound transformation at the free surface of liquid helium II
- 20 March 1980
- journal article
- Published by IOP Publishing in Journal of Physics C: Solid State Physics
- Vol. 13 (8), 1571-1579
- https://doi.org/10.1088/0022-3719/13/8/027
Abstract
A new method has been devised for measuring sound pulse amplitudes in helium, using as a thermometer the variation of sound velocity with temperature. The method has been applied to measure the transformation coefficients of second sound to vapour sound, and vice versa, at the free surface of liquid helium II. The results, interpreted in the light of kinetic theories of evaporation, yield an apparent condensation coefficient of about 0.9. The meaning of this is discussed in relation to the possibility that during evaporation the temperature of the surface excitations of the liquid may differ from the temperature of the bulk excitations.Keywords
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