Component Assignments of the Raman Spectrum from Highly Elongated Silica Glass Filbers

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Abstract
Raman spectra from glass fibers subjected to high tensile stresses (up to 4 GPa) were decomposed into their Gaussian components, which were then assigned to normal vibrational modes of either SiO4 or Si2O molecules using an “isolated molecule" model. Such molecule-related parameters as force constants, Raman coupling constants and the dispersion of the intertetrahedral bond angle were estimated from the frequencies, heights and widths of the components. It is concluded from the analysis that the Raman spectrum change associated with the application of tensile stress arises principally, not from a Si–O bond stretching or Si–O–Si bond angle broadening, but from a change in the tetrahedral angles of the SiO4 molecules constituting silica glass networks.