Dynamics in He at 4 and 8 K from inelastic neutron scattering

From inelastic neutron scattering we determine the dynamic structure factor S(q, omega ) of fluid He at 4 K (1 bar; 19.51 nm super(-3)) and 8 K (18.7 bar; 19.46 nm super(-3)) as a function of frequency omega for wavenumbers 1 < q < 30 nm super(-1). For q less than or approximate to 4 nm super(...

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Bibliographic Details
Published in:Journal of low temperature physics 1996, Vol.105 (1-2), p.149-183
Main Authors: CREVECOEUR, R. M, SMORENBURG, H. E, DE SCHEPPER, I. M
Format: Article
Language:English
Subjects:
Brillouin scattering
Condensed matter: structure, mechanical and thermal properties
Damping
Exact sciences and technology
Flow of fluids
Low temperature effects
Mathematical models
Neutron scattering
Other topics in quantum fluids and solids
liquid and solid helium
Phonons
Physics
Quantum fluids and solids
liquid and solid helium
Rayleigh scattering
Viscoelasticity
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Summary:From inelastic neutron scattering we determine the dynamic structure factor S(q, omega ) of fluid He at 4 K (1 bar; 19.51 nm super(-3)) and 8 K (18.7 bar; 19.46 nm super(-3)) as a function of frequency omega for wavenumbers 1 < q < 30 nm super(-1). For q less than or approximate to 4 nm super(-1), S(q, omega ) is given by the Rayleigh-Brillouin triplet of hydrodynamics. For q > 4 nm super(-1) the central Rayleigh line vanishes and S(q, omega ) is given by the phonon Damped Harmonic Oscillator model similar as in superfluid helium. The phonons are overdamped for a small region near q identical with 20 nm super(-1). At 8 K, helium starts to behave in a visco-elastic manner, similar as seen in classical fluids. We discuss a unifying model that connects the properties of superfluid helium to those of classical fluids.
ISSN:0022-2291
1573-7357
DOI:10.1007/BF00754632