Scattering Investigation of Acoustic Localization in Fused Silica

Small angle neutron time-of-flight spectroscopy and inelastic x-ray scattering results are reported on the acoustic vibrations of fused silica. An expression for the dynamical structure factor is given that successfully describes the scattering from these vibrations, including the boson peak. The data analysis indicates an acoustic localization edge at 1THz, in agreement with the position of the thermal conductivity plateau. Scattering results on another strong glass support the generality of our description.