Correlation effects on Raman scattering from low-energy vibrational modes in glasses. II. Experimental results

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Abstract
New experimental results of low-frequency Raman scattering from different glasses are presented. They are compared to the vibration density of states obtained from inelastic neutron scattering to deduce the light-vibration coupling coefficient C(ω) as a function of the vibration frequency. It was found that C(ω)∝ω2 at very low frequency ω<20 cm−1 in inorganic glasses (SiO2,B2O3) and that C(ω)∝ω at low frequency in polymer glasses and in inorganic glasses for ω≳20 cm−1. Our experimental results for glasses are interpreted by assuming no correlation at very low-frequency and only radial correlation at low-frequency. A full correlation would exist in silica-aerogels in which the effect of random fluctuations would be negligible.