ISSN:
1573-7357
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The dynamic structure factor, S(Q, ω), for wavevectors, 2.0≤Q≤3.6 Å −1 of liquid 4 He in 95% porous aerogel has been measured by inelastic neutron scattering methods. The aerogel was grown with deuterated materials and the multiple scattering involving the aerogel was negligible. S(Q, ω) in the superfluid phase consists of a single peak plus broad intensity at higher energy ω, as in bulk superfluid 4 He. The single peak is identified with the phonon-roton excitation at higher Q. The weight in the peak, ZQ , and the excitation energy dispersion curve, ω Q , has the same basic wavevector dependence as in the bulk. The energy ω Q is 2–3% below the bulk value at the end point and the peak is unobservable beyond Q=3 Å −1 within the present statistical precision. No peak is observed at T=2.3 K in normal 4 He suggesting, as in bulk 4 He, that the characteristic excitation at higher Q is associated with the superfluid phase.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1021818123583
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