Abstract

J. Low Temp. Physics (1998) 113(1-2), 11-18.

Quantum Evaporation from Superfluid ⁴He

C.D.H. Williams

Department of Physics, University of Exeter, Exeter, EX4 4QL (UK).

The quantum evaporation experiments of Brown and Wyatt have been re-analysed in the light of a recent measurement of the high-energy phonon spectrum created by a pulse-heated thin film. Two sources of systematic error become significant at the level of the precision required by this new analysis: firstly, in the detector position which is recalibrated by using large-angle roton evaporation; and secondly, in the liquid height due to capillary action affecting the level-detectors. These effects have been included in an improved simulation of the experiment which has brought the angular dependence of the measured and theoretical phonon-atom evaporation results into agreement within the mechanical tolerances of the apparatus. The re-analysis suggests that the roton-atom evaporation probability increases with wave vector.

Keywords: quantum evaporation, liquid helium.
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