SURFACE CORE-LEVEL SHIFT PHOTOELECTRON DIFFRACTION OF RH(100)

Scanned energy photoelectron diffraction spectra of the clean Rh(100) surface have been measured. The variation of intensity of the bulk and surface components of the 3d(5/2) core level over a photon energy ran ge from 390 to 550 eV was determined for three different geometries. A n energy resolution ranging from 0.23 to 0.45 eV was used in order to clearly resolve the surface shifted peak, which has a surface con leve l shift of 0.64 eV. A preliminary evaluation of the data yields a surf ace relaxation of the first layer normal to the surface equal to -1.4/-3.6%. This is in better agreement with theory than previous LEED I-V measurements: calculations consistently predict a contraction, and LE ED has consistently indicated an expansion.