Dynamical effects as a window into van der Waals interactions in grazing-incidence fast He-atom diffraction from KCl(001)

Abstract

In this paper we address, both experimentally and theoretically, the very grazing scattering of He atoms off KCl(001) with incidence along the (100) channel. Our theoretical model combines a semiquantum description of the scattering dynamics and a high-precision interaction potential. By means of a thorough analysis of the quantum phase for in-plane scattering and rainbow trajectories, we are able to connect the presence of the physisorption well with the significant enhancements of the corrugation and rainbow angle, relative to the hard corrugated wall predictions. We trace this connection to dynamical effects on the incident and scattered beams due to their traversing of the physisorption well. Finally, we show that the inclusion of van der Waals interactions in the potential improves the theoretical accord with experiments for both the corrugation and the rainbow angle.