FINAL-STATE SCATTERING IN ANGLE-RESOLVED ULTRAVIOLET PHOTOEMISSION FROM COPPER

The problem of direct transition intensities in angle-resolved UV phot oelectron spectroscopy is addressed. We demonstrate that the angular d istribution of intensities integrated over the full 3d band of copper is dominated by final-state scattering effects much like those observe d in the diffraction of core level photoelectrons. These UV photoelect ron diffraction effects are very sensitive to the angular momentum cha racter of the valence orbitals that form the band states, and to the a tomic structure of the surface layers. Specifically, we have performed measurements on Cu(lll) and Cu(001) surfaces where we find excellent agreement of experimental angular distributions of integrated d band e mission excited by He I and He II radiation and single-scattering clus ter calculations, involving emission from localized d states, and incl uding proper photon polarizations. At the same time the angle-resolved energy spectra show strong dispersion effects, reflecting the delocal ized character of these band states. This duality may be a further ind ication for the localization of the valence hole upon photoemission.