SI 2P CORE-LEVEL CHEMICAL-SHIFTS AT THE H/SI(111)-(1X1) SURFACE

We calculate the core-level shift of the Si 2p levels for atoms near the H/Si(111)-(1x1) surface. We show that a simple first-order perturbation theory using pseudopotentials and the local-density approximation gives good results for the photoemission spectra of the core electrons. The electric-dipole matrix elements for the levels are also calculated. The results are in good agreement with a recent high-resolution angle-resolved photoemission-spectroscopy measurement and allow us to interpret some previously unexplained experimental peaks.