Surface localized states and the Fermi contour of Pd(001)

Angle-resolved photoemission measurements of the surface localized electronic states of the clean Pd(001) surface are presented. Several surface localized levels were observed, in qualitative agreement with an existing surface band-structure calculation. In particular, a state was observed which crosses the Fermi level (${\mathit{E}}_{\mathit{F}}$) near the X¯ point of the surface Brillouin zone. The segment of the Fermi contour derived from this crossing lies largely within a gap in the projected bulk Fermi surface and is parallel to the Brillouin-zone edge. The nesting properties of this segment of the Fermi contour suggest the possibility of a fairly strong electronic coupling to phonon excitations.