The Raman coupling function in permanently densified GeO2 glasses

We report on a Raman and inelastic neutron scattering investigation of the vibrational dynamics of permanently densified v-GeO2 glasses. The comparison between the two techniques allows us to derive the Raman coupling function C(omega). This quantity shows a linear frequency dependence in the boson peak range and is not affected by the sample densification. We thus show that Raman spectroscopy can be used as a complementary technique to neutron scattering as a probe of the density of vibrational states in glasses. The evolution of the Raman spectra with the density of the studied samples compares well with the neutron results, confirming the existence of a master curve associated to a single scaling parameter.