The evaporation of atoms from the surface of superfluid {sup 4}He by rotons

Journal Article · Wed Nov 01 04:00:00 EST 1995 · Journal of Low Temperature Physics

DOI:https://doi.org/10.1007/BF00753350· OSTI ID:183415

Forbes, A; Wyatt, A ^[1]

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1. Univ. of Exeter (United Kingdom)

A beam of rotons is directed toward the liquid surface at normal incidence. At the surface some rotons will evaporate atoms, with a wave-vector dependant probability p(q). The kinetic energy of the evaporated atom is equal to the difference in energy between the energy of the roton and the binding energy of a {sup 4}He atom to the surface (7.16 K). The atoms which are evaporated are detected by a bolometer above the surface. The path length of the roton in the liquid, and the atom in the vacuum, are varied by changing the liquid level in the cell. By thus changing the liquid level, we change the flight time between heater and bolometer for a given wavevector of roton. We analyse the time-of-flight spectra received by the bolometer to reveal the product n(q)p(q) where n(q) is the distribution of rotons. If we assume that n(q) reflects the temperature of the phonons in the heater used to inject the rotons, we can deduce p(q). The resulting p(q) shows an unexpected decrease towards roton minimum at q < 2.1 {angstrom}{sup -1}.

• Sponsoring Organization: USDOE
• OSTI ID: 183415
• Report Number(s): CONF-950676--
• Journal Information: Journal of Low Temperature Physics, Journal Name: Journal of Low Temperature Physics Journal Issue: 3-4 Vol. 101; ISSN JLTPAC; ISSN 0022-2291
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
BINDING ENERGY
BOLOMETERS
EVAPORATION
HELIUM 4
PHONONS
ROTONS
SUPERFLUIDITY
SURFACE PROPERTIES