ADSORBATE-INDUCED SURFACE RESONANCES OBSERVED IN PHOTOEMISSION FROM A (SQUARE-ROOT2 X SQUARE-ROOT2)R45-DEGREES SULFUR LAYER ON PD(100)

Angular-resolved photoemission spectra from a ( 2 × 2)R45° sulphur layer on Pd(100) reveal peaks independent of photon energy, which show strong dispersion in the electron energy range 3...9 eV relative to the vacuum level. The appearance of these levels can be correlated with absolute gaps in the projected bulk band structure of palladium. We interpret these features, which are also observed in secondary electron emission, as adsorbate-induced surface resonances above EF. The sulphur 3p-derived levels below EF show strong dispersion effects in the [110] but not in the [100] crystal azimuth. The projected band structure also shows that sd hybridisation gives rise to an absolute gap at approximately this energy in the [110] (ΓX) direction. © 1979.