q dependence of low-frequency Raman scattering in silica glass

Accurate measurements of the dependence of low-frequency Raman scattering o n the scattering angle were performed in two silica glasses. By a compariso n of spectra measured at a large scattering angle (close to back scattering ) and a small one (close to forward scattering), we for the first time obse rved a q dependence of the low-frequency light scattering in glasses. From the magnitude of the effect, the vibration correlation length is estimated and compared with results from the picosecond optical technique; a reasonab le agreement is found. [S0031-9007(99)09266-2].