Résumé
In the low-frequency regime, the Raman spectrum of most glasses is dominated by a strong broad line which is usually called the Boson peak. The physical origin of this peak is still a matter for discussion. Several attempts have been made in order to connect the Boson peak to the vibrational density of states. Various interpretations have been proposed in recent years, in which the Boson peak is related to structural characteristics. In order to investigate the relationship between the vibrational dynamics and the medium-range order in glasses, we have studied the Brillouin and Raman scattering of several samples of oxide glasses prepared and stabilized under very different conditions. A study of the first sharp diffraction peak (FSDP) on the same samples shows that the two features, FSDP and Boson peak, are not clearly correlated. The results are discussed on the basis of the relationship between the mean free path of phonons and the low-frequency Raman intensity.