Journal of Low Temperature Physics

, Volume 95, Issue 3–4, pp 441–480 | Cite as

Raman scattering from He II near the two-roton threshold. II. Comparison with experiments

  • Masahiro Nakajima
  • Hiroshi Namaizawa


Based on the new formalism which is developed in the preceding paper and is free from the difficulty with which the conventional theories could not cope, we shall examine experimental Roman spectra of He II near the two-roton threshold. The intensity spectrum is determined by the generalized density of states of interacting rotons (GDOSIR). For the form factor of a roton-pair creation from the atomic density fluctuation which appears in GDOSIR, a power law in total energy is assumed. After investigating what types of characteristic structures and how they appear in GDOSIR as α, the power of the form factor, and g, the coupling constant, change, we shall perform line shape analysis between theory and experiment by varying g and Δ R , the roton-minimum energy, by including the instrumental width. It is found that α in the margin 0⩽α ≲1/2 well reproduces experiments at SVP, 5, 10, 15 and 20 kg/cm2, the margin including that set by the direct roton-roton scattering experiment, namely α ≈ 1/2. Further it also includes the conventional theories as a special case (α = 0), thereby solving the puzzle that the theories in error could have predicted the Roman feature so successfully. In addition the values of the coupling constant obtained by the Roman data here are in remarkable correspondence with those determined by the roton-roton scattering, thereby suggesting a possibility for the form of the interaction with α ≈ 1/2 to lead to a unified understanding of roton dynamics. Further the results for Δ R are not only in close agreement with each other for α in the Roman margin but also with the neutron results, from SVP to 20 kg/cm2. Therefore the Roman data alone can afford reliable information on the fundamental parameter of elementary excitations in He II. The results will also be presented for the bound-state energy and the relative peak intensity as functions of pressure and suggestions for experiment are given both for Raman and direct roton-roton scattering which may help narrowing the margin for α further.


Form Factor Density Fluctuation Shape Analysis Atomic Density Generalize Density 
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Copyright information

© Plenum Publishing Corporation 1994

Authors and Affiliations

  • Masahiro Nakajima
    • 1
  • Hiroshi Namaizawa
    • 1
  1. 1.Institute of Physics, College of Arts and SciencesUniversity of TokyoTokyoJapan

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