THE SURFACE CORE-LEVEL SHIFT OF THE NB(110) SURFACE

The surface core-level shift (SCLS) of the Nb(110) surface has been de termined by means of high-resolution core-level photoelectron spectros copy of the Nb 3d(5/2) core level. A SCLS of 180 +/- 15 meV towards hi gher binding energy with respect to the bulk component was estimated b y curve fitting the Nb 3d(5/2) core-level spectra taken using several photon energies. The sign of the SCLS agrees with recent ab initio cal culations including both initial- and final-state effects, but the shi ft is significantly smaller than predicted in these calculations.