Phonon-assisted resonances with surface bound states are shown to give important effects in time-of-flight spectra of He scattered from a LiF (100) surface. The comparison with theory indicates that inelastic resonances produce sharp distortions in the response of the surface phonon spectrum. At low temperature, theory predicts that resonances can locally amplify the phonon response by an order of magnitude.

• Received 23 December 1982

DOI:https://doi.org/10.1103/PhysRevLett.50.1854