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 order 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 finally, between 450 and 550 cm(-1), C(v) sharply decreases. The results are discussed 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.