%0 Journal Article
%T The Vibrations of Vitreous Silica Observed in Hyper-Raman Scattering
%+ Laboratoire Charles Coulomb (L2C)
%+ Laboratoire de Dynamique Interactions et Réactivité (LADIR)
%A Hehlen, Bernard
%A Simon, Grégory
%< avec comité de lecture
%Z L2C:12-247
%@ 0377-0486
%J Journal of Raman Spectroscopy
%I Wiley
%V 43
%N 12
%P 1941
%8 2012-12-14
%D 2012
%R 10.1002/jrs.4110
%K silica
%K hyper-Raman
%K vibrations
%K boson peak
%Z Physics [physics]/Condensed Matter [cond-mat]/Disordered Systems and Neural Networks [cond-mat.dis-nn]Journal articles
%X Hyper-Raman scattering (HRS) is performed in v-SiO2, and the results are compared to RS and infrared absorption data. Mode analyses are tested based on two models, either the local C2v symmetry of the Si-O-Si bonds or the Td symmetry of the SiO4 tetrahedra. The HRS boson-peak (BP) signal is dominated by the quasi-local librations of tetrahedra. However, we find that it also contains a weak dipolar contribution with a different spectral signature, suggesting that the BP modes are not fully hybridized. The transverse optic (TO) modes can be assigned to molecular-like excitations according to either model, with the exception of the lowest frequency TO4 which involves highly cooperative Si-O-Si motions. On the opposite, the strong scattering from all longitudinal optic (LO) modes clearly follows the average isotropic medium ∞∞m selection rules. This long range cooperativity presumably results from the associated internal electric field. Finally, the strong LO HRS signals enabled observing a new longitudinal component at 1078 cm−1. Through the example of v-SiO2, the article also highlights new perspectives provided by HRS for the description of the vibrations in disordered materials in general.
%G English
%L hal-00767212
%U https://hal.science/hal-00767212
%~ UPMC
%~ CNRS
%~ L2C
%~ INC-CNRS
%~ MIPS
%~ UNIV-MONTPELLIER
%~ SORBONNE-UNIVERSITE
%~ ALLIANCE-SU
%~ UM-2015-2021
%~ TEST2-HALCNRS