High-resolution He atom inelastic-scattering experiments provide evidence for the shear horizontal surface phonons on the in situ cleaved NaCl(001) surface. The measurements were made in a sagittal plane along the [210] azimuth and beyond the first surface Brillouin zone. A slab calculation using the breathing shell model and a surface perturbation that fulfills invariance conditions is used to identify the polarizations of the observed surface phonons.

• Received 8 July 1996

DOI:https://doi.org/10.1103/PhysRevB.54.17866