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


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.


Experimental Study Energy Spectrum Magnetic Material Quadratic Form Theoretical Prediction 
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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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