Raman light-to-vibration coupling coefficient of v-SiO2 in spectral interval range up to 600 cm(-1)

Raman and inelastic neutron spectra of vitreous silica were compared in ord er to derive the Raman light-to-vibration coupling coefficient C(v) in the spectral interval between 10 and 600 cm(-1). C(v) shows different frequency dependences in different spectral regions: between 30 and 110 cm(-1), C(v) proportional to v; between 110 and 450 cm(-1), C(v) is constant; and final ly, between 450 and 550 cm(-1), C(v) sharply decreases. The results are dis cussed in the frame of the existing models for the vibrational excitations in vitreous silica. The crossover frequency of C(v) at similar to 110 cm(-1 ) is interpreted as the onset of phonon localization in the sense of Ioffe- Regel rule. (C) 2001 Elsevier Science Ltd. All rights reserved.