Raman-Scattering Measurements of Acoustic Superlocalization in Silica Aerogels

Abstract

Results of depolarized Raman spectroscopy on fractal silica aerogels are presented at frequencies from 0.3 to 50 ${\mathrm{cm}}^{\ensuremath{-}1}$. Three distinct vibration regimes are observed. In the fracton range, a power-law dependence of the Raman susceptibility on the frequency is found. It allows a determination of the superlocalization exponent ${d}_{\ensuremath{\varphi}}$. Alternatively, with use of the "resistance" expression for the exponent ${d}_{\ensuremath{\varphi}}$, a spectral dimension $\stackrel{-}{\overline{d}}$ in fair agreement with previous measurements results.