The vibrations of vitreous silica observed in hyper-Raman scattering
Article first published online: 15 JUL 2012
Copyright © 2012 John Wiley & Sons, Ltd.
Journal of Raman Spectroscopy
Volume 43, Issue 12, pages 1941–1950, December 2012
How to Cite
Hehlen, B. and Simon, G. (2012), The vibrations of vitreous silica observed in hyper-Raman scattering. J. Raman Spectrosc., 43: 1941–1950. doi: 10.1002/jrs.4110
- Issue published online: 14 DEC 2012
- Article first published online: 15 JUL 2012
- Manuscript Accepted: 22 APR 2012
- Manuscript Revised: 5 APR 2012
- Manuscript Received: 7 MAR 2012
- boson peak
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. Copyright © 2012 John Wiley & Sons, Ltd.