Threshold resonances in classical chaotic atom-surface scattering

A classical picture of threshold resonances in diffractive systems is provided in the light of a new classical singularity recently predicted for atom surface scattering, the skipping singularity. As an illustration of these dynamics, application to the scattering of He atoms by the stepped Cu(115) surface is presented using both a hard corrugated one-dimensional wall and a corrugated Morse potential. It is also emphasized that these resonances are observable for highly corrugated surfaces or for surfaces with weak corrugation but at incident conditions where multiple scattering is important. (C) 1997 Elsevier Science B.V.