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Journal of Low Temperature Physics

, Volume 27, Issue 5–6, pp 851–872 | Cite as

Experimental studies of the excitation spectrum of3He-4He mixtures using neutron inelastic scattering

  • P. A. Hilton
  • R. Scherm
  • W. G. Stirling
Article

Abstract

Neutron inelastic scattering techniques have been used to study the excitation spectrum of mixtures containing 6%, 12%, and 25% of3He in4He at 0.75 K. The 6% mixture has also been investigated at temperatures of 0.6, 1.0, and 1.5 K. The measurements have been made in the wave-vector transfer rangeQ=0.8−2.3 Å−1. The energy spectra observed contain two principal features, which are interpreted as scattering from (a) phonon-roton excitations arising from the4He, and (b) quasiparticle-quasihole excitations arising from the3He. In the dilute3He-4He mixture, our results indicate a3He particle-hole continuum which deviates from the quadratic form, proposed by Landau and Pomeranchuk, and which lies below the4He phonon-roton dispersion curve. However, we are unable to say whether or not the continuum exhibits a minimum as a function of energy, as has recently been proposed by several authors, because we were unable to resolve the scattering from the particle-hole continuum forQ⪝1.7 Å−1. In this region ofQ space the energy spectra are dominated by the roton excitations. We have also determined the shifts in energy and increases in linewidth of the phonon-roton excitations relative to those of pure4He and compared these measurements to several theoretical predictions.

Keywords

Experimental Study Energy Spectrum Magnetic Material Quadratic Form Theoretical Prediction 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Publishing Corp 1977

Authors and Affiliations

  • P. A. Hilton
    • 1
  • R. Scherm
    • 2
  • W. G. Stirling
    • 2
  1. 1.University of EdinburghUK
  2. 2.Institut Laue-LangevinGrenobleFrance

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