Phonon and Roton-Induced Evaporation
We present results which show that the excitation-surface atom interaction is a single quantum process and that both energy and the component of momentum parallel to the liquid surface are conserved. The essence of our experiments is to create a beam of excitations in the bulk liquid 4He and let them propagate to the free surface. A bolometer in the space above the liquid detects atoms which leave the surface. The excitations in the liquid 4He are not scattered by ambient excitations at 0.1 [K] and the saturated vapour pressure is so low that the evaporated atoms can travel ballistically to the detector. Using time of flight measurements we can estimate the energy of the excitation and the evaporated atom and hence analyse the interaction at the surface.
KeywordsDispersion Curve Saturated Vapour Pressure Solid Helium Atom Signal Flight Measurement
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