PHOTOELECTRON DIFFRACTION AT LOW ENERGIES - THE APPLICABILITY OF SINGLE SCATTERING CALCULATIONS

The energy dependence of the 4f core level photoemission intensity fro m Ta(100) has been modeled at low electron kinetic energies using the single scattering cluster (SSC) approximation. The results show a stri kingly similar shape to that of a full multiple scattering calculation , particular at electron kinetic energies less than 75 eV. A compariso n with the experimentally measured surface/bulk core level intensity o scillations indicates that the first interlayer spacing of the Ta(100) surface is contracted by 11+/-3%, consistent with previous determinat ions. These results suggest that SSC calculations can model low energy photoelectron diffraction data from surface shifted core levels with sufficient accuracy to enable a quantitative structural determination of clean, unreconstructed surfaces.