Lattice vibrations of para-hydrogen impurities in a solid deuterium matrix: An inelastic neutron scattering study (Articolo in rivista)

Type
Label
  • Lattice vibrations of para-hydrogen impurities in a solid deuterium matrix: An inelastic neutron scattering study (Articolo in rivista) (literal)
Anno
  • 2007-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1103/PhysRevB.76.174304 (literal)
Alternative label
  • Colognesi D. (1); Celli M. (1); Ramirez-Cuesta A. J. (2); Zoppi M. (1) (2007)
    Lattice vibrations of para-hydrogen impurities in a solid deuterium matrix: An inelastic neutron scattering study
    in Physical review. B, Condensed matter and materials physics
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Colognesi D. (1); Celli M. (1); Ramirez-Cuesta A. J. (2); Zoppi M. (1) (literal)
Pagina inizio
  • 174304-1 (literal)
Pagina fine
  • 174304-13 (literal)
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  • 76 (literal)
Rivista
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  • 13 (literal)
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  • 17 (literal)
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • 1) Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, Sezione di Firenze, via Madonna del Piano 10, Sesto Fiorentino, 50019 Firenze, Italy 2) ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom (literal)
Titolo
  • Lattice vibrations of para-hydrogen impurities in a solid deuterium matrix: An inelastic neutron scattering study (literal)
Abstract
  • In the present study, we report inelastic neutron scattering measurements from para-hydrogen defects in solid normal deuterium at three different concentrations (between 3% and 11%) using the time-of-flight spectrometer TOSCA-II. The measured double-differential cross sections give access to the self-inelastic structure factors for the H2 centers of mass. Corrected experimental data, analyzed through the Young-Koppel model and the Gaussian approximation, are transformed into defect densities of phonon states, which come out to be broad, structured, and nearly concentration independent. Two experimentally determined Bose-corrected spectral moments are found to be in agreement with independent estimates, providing a strong validation of our data reduction procedure. Subsequently, experimental phonon spectra are compared to three calculations, namely, a simple harmonic model at infinite dilution, a more advanced harmonic model with concentration effects, and finally a lattice dynamics simulation based on self-consistent phonon and coherent potential approximations. However, while the first part of the defect spectral density, attributed to the propagating modes, turns out to be roughly explained, the localized part is properly described by none of these models, except for its mean frequency position. The large overall width appears so far impossible to be reproduced, representing a challenge for the physicists involved in quantum dynamics simulations. (literal)
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