FULL-HEMISPHERICAL PHOTOELECTRON-DIFFRACTION DATA FROM CU(001) - ENERGY-DEPENDENCE AND COMPARISON WITH SINGLE-SCATTERING-CLUSTER SIMULATIONS

Angular distributions of several photoelectron and Auger transitions have been measured above a Cu(001) single crystal at 16 different kinetic energies between 60 and 1740 eV. The results are presented as 2pi full-solid-angle intensity maps-diffractograms-that permit a clear representation of the relative importance of various scattering processes at each energy and the evolution of intensity patterns with energy. The experiments are compared with single-scattering-cluster (SSC) simulations performed at corresponding energies. This serves to probe the accuracy of the SSC formalism over a vast energy and angular range and to illustrate the role of the angular momentum of the final state, polarization effects, and temperature effects. Rather good agreement is found for positions of angular patterns down to very low energies, with problems mainly in relative intensities. The sensitivity of low-energy diffraction patterns to bond lengths is demonstrated.