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Inelastic Neutron Scattering from Lattices, Molecular Crystals and Powders

  • M. Warner
  • J. M. F. Gunn
Part of the NATO ASI Series book series (NSSB, volume 112)

Abstract

New neutron sources provide epithermal neutrons well suited in energy to investigate the internal motions of molecules. With these higher energies also come high momenta. Do extreme limits of these two factors yield apparent quasi-free behaviour for the scattering centres? Asymptotic analysis for model systems of harmonic lattices, isolated oscillators and oscillators in lattices answer this qualitative question. Exact numerical results reveal how good approximate methods actually are. A lot of structure in oscillator lines can result from kinematic effects of the lattice environment and is not revealed by approximate treatments. This is a possible artifact to be first removed from experimental interpretation before more subtle explanations of splittings and shifts are invoked.

The advantages offered by high momentum transfer (neutron) spectroscopy over usual spectroscopic techniques are explained, as are the problems thereby encountered when then dealing with powders. A systematic technique involving the use of displacement tensors in spherical coordinates yields simple, exact results rather than the usual expansions or numerics.

Keywords

Saddle Point Wave Packet Momentum Transfer Neutron Source Gaussian Approximation 
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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References

  1. 1.
    Howard J and Waddington T C: Advances in Infrared and Raman Spectroscopy, Chapter 3, Vol. 7. Clark R J H and Hester R E (eds ). Heyden and Sons, 1980.Google Scholar
  2. 2.
    Springer T: Hydrogen in Metals I, Chapter 4. Alefeld G and Volkl J (eds). Berlin: Springer-Verlag, 1978.Google Scholar
  3. 3.
    Gunn J M F and Warner M: Z Phys B (in the press)Google Scholar
  4. 4.
    Sjolander A, Art. fur Fysik 14, 315 (1958).Google Scholar
  5. 5.
    Tomkinson J, Warner M and Taylor A D: Mol. Phys 51, 381 (1984)ADSCrossRefGoogle Scholar
  6. 6.
    Lovesey S W, “Theory of Neutron Scattering from Condensed Matter”, Vol. I. Oxford: Clarendon Press, 1984.Google Scholar
  7. 7.
    Egelstaff P A and Schofield P, Nucl. Sci. Eng. 12, 260 (1962).Google Scholar
  8. 8.
    Schofield P and Hassitt A, Progress in Nuclear Energy, Series I, Vol 3, page 194; London: Pergamon Press, 1959.Google Scholar
  9. 9.
    Warner M, Lovesey S W and Smith J, Z.f.Phys. B51, 109–126 (1983).ADSCrossRefGoogle Scholar
  10. 10.
    Wick G C, Phys. Rev. 94, 1228 (1954).MathSciNetADSMATHCrossRefGoogle Scholar
  11. 11.
    Griffin A and Jobic H: J. Chem. Phys. 75, 5940 (1981).ADSCrossRefGoogle Scholar
  12. 12.
    Jobic H, Ghosh R E and Rencuprez A: J Chem. Phys. 75, 4025 (1981).ADSCrossRefGoogle Scholar
  13. 13.
    Vibrational spectroscopy on a pulsed neutron source employs relatively high momentum transfers, for example: Boland B C, Mildner D F R, Stirling G C, Bunce L J, Sinclair R N and Windsor C G:Nucl. Inst. Meth. 154, 349 (1978).CrossRefGoogle Scholar
  14. 14.
    The limitation to workingat relatively high momentum transfer Q(.5A-1) when performing neutron spectroscopy is analysed, for example: Brugger R M, Strong K A and Grant D M: p.323 Neutron Inelastic Scattering, Vol.II. Vienna: International Atomic Energy Agency, 1968.Google Scholar
  15. 15.
    Placzek G: Phys. Rev. 86, 377 (1952)ADSMATHCrossRefGoogle Scholar
  16. Placzek G: Phys. Rev. 93, 895 (1954)ADSCrossRefGoogle Scholar
  17. Placzek G: Phys. Rev. 105, 1240 (1957).MathSciNetADSMATHCrossRefGoogle Scholar
  18. 16.
    Dolling G and Powell B M: Proc. Roy. Soc. Lond. A319, 209 (1970).ADSCrossRefGoogle Scholar
  19. 17.
    Reynolds P.A., Kjems J.K. and White J.W. J. Chem. Phys 56, 2972 (1972).Google Scholar
  20. 18.
    Thomas M.W. and Ghosh R.E. Mol. Phy. 29 (1975).Google Scholar
  21. 19.
    Wright C.J J Chem. Soc. Faraday II, 73, 1497 (1976).CrossRefGoogle Scholar
  22. 20.
    Warner M. Colloid and Polymer Science, 261, 508 (1983).CrossRefGoogle Scholar
  23. 21.
    Berne B.J. and Pecora R. “Dynamic Light Scattering,” Chichester, Wiley and Sons (1976).Google Scholar
  24. 22.
    Davydov A.S. “Quantum Mechanics,” Oxford, Pergamon (1965).Google Scholar
  25. 23.
    Howard J., Tomkinson J., Eckert J., Goldstone J. and Taylor A.D. Rutherford Appleton Laboratory Report RL-83–032 and Mol. Phys. (submitted).Google Scholar
  26. 24.
    Howard J. and Tomkinson J. Chem. Phys. Letts. 98, 239 (1983)ADSCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1984

Authors and Affiliations

  • M. Warner
    • 1
  • J. M. F. Gunn
    • 1
  1. 1.Rutherford Appleton LaboratoryChilton, Didcot, OxonUK

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