Scattering of He Atoms from a Microstructured Grating: Quantum Reflection Probabilities and Diffraction Patterns.

The quantum reflection measured previously by Zhao et al. ( Phys. Rev. A 2008 , 78 , 010902(R) ) for the scattering of He atoms off of a microstructured grating is described and analyzed theoretically. Using the close-coupling formalism with a complex absorbing potential and describing the long-range interaction in terms of the Casimir-van der Waals potential, we find probabilities and diffraction patterns that are in fairly good agreement with the experimental results. The central outcomes of this study are two-fold. First is the theoretical confirmation that, indeed, the phenomenon of quantum reflection may be detected not only through the elastic peak but also in terms of a quantum reflected diffraction pattern. Second, we demonstrate that the phenomenon of quantum reflection is the result of a coherent process where all of the potential regions are involved on an equal footing. It is a nonlocal property and cannot be related only to the long-range badlands region of the potential of interaction.