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(122) Production(s) de VACHER R.
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Hyper-raman scattering from vitreous boron oxide: Coherent enhancement of the boson peak
Auteur(s): Simon Guilhem, Hehlen B., Courtens E., Longueteau E., Vacher R.
(Article) Publié:
Physical Review Letters, vol. 96 p.105502 (2006)
Résumé: Hyper-Raman scattering spectra of vitreous B2O3 are compared to Raman scattering ones. Particular attention is given to the low-frequency boson peak which relates to out-of-plane rigid librations of planar structural units, mostly boroxols. While the Raman strength can be accounted for by the motions of single units, the hyper-Raman signal exhibits a unequaled enhancement due to coherent librations of several boroxols. This important distinction is explained by the different symmetry properties of the polarizability and hyperpolarizability tensors of the structural units.
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Acoustic Damping in Li 2 O-2B 2 O 3 glass observed by inelastic x-ray and optical Brillouin scattering
Auteur(s): Ruffle B., Guimbretiere Guillaume, Courtens E., Vacher R., Monaco G.
(Article) Publié:
Journal Of Non-Crystalline Solids, vol. 352 p.4589-4593 (2006)
Résumé: The dynamic structure factor of lithium-diborate glass has been measured at several values of the momentum transfer Q using high resolution inelastic X-ray scattering. Much attention has been devoted to the low-Q-range, below the observed Ioffe-Regel crossover q(IR) similar or equal to 2.1 nm(-1). We find that below q(IR), the linewidth of longitudinal acoustic waves increases with a high power of either Q, or of the frequency Omega, up to the crossover frequency Omega(IR) similar or equal to 9 meV that nearly coincides with the center of the boson peak. This new finding strongly supports the view that resonance and hybridization of acoustic waves with a distribution of rather local low frequency modes forming the boson peak is responsible for the end of acoustic branches in strong covalent glasses. Further, we present high resolution Brillouin light-scattering data obtained at much lower frequencies on the same sample. These clearly rule out a simple Omega(2)-dependence of the acoustic damping over the entire frequency range. (c) 2006 Elsevier B.V. All rights reserved.
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Glass-specific behavior in the damping of acoustic-like vibrations
Auteur(s): Ruffle B., Guimbretiere Guillaume, Courtens E., Vacher R., Monaco G.
(Article) Publié:
Physical Review Letters, vol. 96 p.045502 (2006)
Résumé: High frequency sound is observed in lithium diborate glass, Li2O-2B(2)O(3), using Brillouin scattering of light and x rays. The sound attenuation exhibits a nontrivial dependence on the wave vector, with a remarkably rapid increase towards a Ioffe-Regel crossover as the frequency approaches the boson peak from below. An analysis of literature results reveals that the boson-peak frequency is closely related with a Ioffe-Regel limit for sound in many glasses. We conjecture that this relation, specific to glassy materials, might be rather common among them.
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Glass-specific behavior in the damping of acoustic like vibrations
Auteur(s): Ruffle B., Guimbretiere Guillaume, Foret M., Courtens E., Vacher R., Monaco G.
Conference: X International workshop on disordered systems (Molveno, Italy, FR, 2006-03-17)
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Spectroscopie Hyper-Raman dans les Verres d'Oxydes : nature des vibrations et exaltation du pic boson
Auteur(s): Simon Guilhem, Hehlen B., Courtens E., Vacher R.
Conference: JMC 10 (Toulouse, France, FR, 2006-08-28)
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Glass-Specific Behavior in the Damping of Acoustic Like Vibrations
Auteur(s): Ruffle B., Guimbretiere Guillaume, Foret M., Courtens E., Vacher R., Monaco G.
Conference: XI Conference on the Physics of Non-Crystalline Solids (Rhodes, Greece, FR, 2006-10-29)
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Hyper-Raman scattering from vitreous boron oxide. Nature of the vibrations and coherent enhancement of the boson peak
Auteur(s): Hehlen B., Simon Guilhem, Vacher R., Courtens E.
Conference: XI Conference on the Physics of Non-Crystalline Solids (Rhodes, Greece, FR, 2006-10-20)
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