THE RELATIVISTIC LAYER-RESOLVED ELECTRONIC-STRUCTURE AND PHOTOEMISSION OF THE ADSORBATE SYSTEM XE PT(111)/

For the (square-root 3 x square-root 3)R30-degrees commensurate physis orption system Xe/Pt(111), the k(parallel-to-, layer- and double-group -symmetry-resolved density of states (LDOS) as well as spin-resolved n ormal photoemission spectra for circularly and linearly polarized ligh t have been calculated by means of a fully relativistic Green function formalism. Comparison with the LDOS obtained for an isolated Xe monol ayer shows that the m(j) splitting of the 5P3/2-derived states of the Xe adsorbate is almost exclusively due to the lateral interaction with in the Xe layer. In contrast, Pt-derived features are strongly determi ned by the Xe overlayer via 'surface umklapp': firstly, electronic sta tes localized in the two topmost Pt monolayers; and secondly, photoemi ssion features originating from umklapped Pt bulk initial states. For circularly polarized light, we obtain very good agreement with experim ent with regard to peak positions and sign of the spin polarization. S ubstantial discrepancies in absolute polarization values are ascribed to Auger-like electron-hole processes and call for an extension of our photoemission theory to incorporate these additional excitation chann els. For linearly s-polarized light, the calculated spin polarization spectra depend very strongly on the lateral position of the Xe layer r elative to the substrate.