An examination of the use of wave packets for the calculation of atom diffraction by surfaces

We use analytic models, valid for neutron scattering, and numerical calculations to examine a method proposed by Drolshagen and Heller for computing atom diffraction from surfaces. Our main concern is the manner in which the use of narrow packets, causing a partial coherence of the incident beam, might affect the differential intensity. We find that the demands of representing beam coherence correctly conflict with the requirements for the validity of the propagation scheme. We suggest some improvements that should increase the reliability of the method without affecting greatly its remarkable computational and conceptual advantages.