Inelastic neutron scattering by quasi-local vibrations interacting with sound waves in glasses

Abstract

By taking into account both long-wave acoustic phonons and strongly anharmonic low-frequency quasi-local vibrations (QLV), the general double-differential cross section for inelastic neutron scattering in glasses is derived. In the framework of the appropriate pseudo-spin model of a glass, QLV scattering intensities of both the resonant and relaxation types are evaluated. It is shown that, in the range of low frequencies (2-3 meV), the resonant-like density of QLV states is comparable with the density of phonon states as well as corresponding rather closely to the neutron-measured dominant low-frequency ('additional') density of vibrational states in glasses.