Angular distributions of Auger electrons and of photoelectrons emitted at high (>500 eV) and low (<100 eV) kinetic energies are compared. The high-energy patterns can be interpreted as forward-projected images of real space crystal geometry. At low energies, the angular distributions are dominated by diffraction effects, and the structural information is no longer obvious. On the other hand, the sensitivity to the geometry and the atomic composition of the surface is here dramatically enhanced. Moreover, the angular momentum character of the source wave strongly influences these patterns.

• Received 19 March 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.1947