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Details of Grant 

EPSRC Reference: GR/L29149/01
Title: ROTON QUANTUM EVAPORATION
Principal Investigator: Wyatt, Professor A
Other Investigators:
Williams, Dr CDH
Researcher Co-Investigators:
Project Partners:
Department: Physics
Organisation: University of Exeter
Scheme: Standard Research (Pre-FEC)
Starts: 01 January 1997 Ends: 31 December 1999 Value (£): 238,151
EPSRC Research Topic Classifications:
Quantum Fluids & Solids
EPSRC Industrial Sector Classifications:
Related Grants:
Panel History:  
Summary on Grant Application Form
With the development of credible models of Quantum Evaporation which are producing quantitative predictions of the probability of the various excitation-atom processes, there is a need for new experiments that can provide data to compare with theory. Beams of ballistic rotons can be created but their flux cannot be measured, so the probability of evaporation cannot be deduced. We propose an experiment in which atoms are directed at a 'free standing' slab of liquid helium and the atoms which are evaporated from the far side, are detected. The condensing atoms produce rotons which propagate ballistically across the slab and evaporate atoms on the far side. As the probability of the atom-roton process is the same as that for roton to atom we do not need to measure the intermediate roton flux. We also propose to develop a black-body source of rotons, characterise it, and then use it to establish the existence of R-rotons and their quantum evaporation. The lack of evidence for ballistic R-rotons is a major enigma. Ripplon production is a competing process to evaporation and we propose an experiment to measure it.
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Organisation Website: http://www.ex.ac.uk