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 physisorption system Xe/Pt(111), the k(parallel-to-, layer- and double-group-symmetry-resolved density of states (LDOS) as well as spin-resolved normal photoemission spectra for circularly and linearly polarized light have been calculated by means of a fully relativistic Green function formalism. Comparison with the LDOS obtained for an isolated Xe monolayer shows that the m(j) splitting of the 5P3/2-derived states of the Xe adsorbate is almost exclusively due to the lateral interaction within the Xe layer. In contrast, Pt-derived features are strongly determined by the Xe overlayer via 'surface umklapp': firstly, electronic states localized in the two topmost Pt monolayers; and secondly, photoemission features originating from umklapped Pt bulk initial states. For circularly polarized light, we obtain very good agreement with experiment with regard to peak positions and sign of the spin polarization. Substantial 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 channels. For linearly s-polarized light, the calculated spin polarization spectra depend very strongly on the lateral position of the Xe layer relative to the substrate.