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 t he H/Si(111)-(1x1) surface. We show that a simple first-order perturba tion theory using pseudopotentials and the local-density approximation gives good results for the photoemission spectra of the core electron s. The electric-dipole matrix elements for the levels are also calcula ted. The results are in good agreement with a recent high-resolution a ngle-resolved photoemission-spectroscopy measurement and allow us to i nterpret some previously unexplained experimental peaks.