The influence of quasilocal vibrations on the far-infrared spectra of glasses is investigated under the supposition that the quasilocal vibrations are directly inactive in the attenuation. It is shown that taking into account phonon-quasilocal-vibration coupling and both medium- and short-range structure of the inhomogeneities of a photon-phonon coupling parameter can give rise to an attenuation curve similar to one observed for a-${\mathrm{SiO}}_2$ and related materials.

• Received 4 June 1993

DOI:https://doi.org/10.1103/PhysRevB.49.109