A new elastic surface resonance has been observed in angular distributions of He atoms scattered from a single crystal surface NaCl(001). The process has been identified as a coherent selective adsorption into one of the surface bound states followed by incoherent scattering from defects into the continuum. The reverse process has also been identified. These resonances open up possibilities for other highly defined two-dimensional elastic and inelastic surface scattering experiments.

• Received 7 October 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.1508