Abstract
High-resolution neutron inelastic scattering studies of thewavevector and temperature dependence of the excitation spectrum of4He in the superfluid and normal-fluid phases have been made inthe wavevector region `beyond the roton', 2.0<Q<3.6 Å-1, at a pressure of 20 bar. The scattering in this regionexhibits two separate components: a sharp peak at low energies anda broader continuum at higher energies. The relative intensity ofthese two peaks is Q-dependent. We find that the two-rotonenergy, 2Δ, is never exceeded by the sharp peak at thispressure. The data are compared with the density-quasiparticle modelof Glyde and Griffin and a tentative analysis of the temperaturedependence of the condensate fraction n0 is made.
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