An ultraviolet photoelectron spectroscopic study of the interaction of potassium with carbon monoxide and benzene on the Pt(111) surface

The interaction of potassium with carbon monoxide and benzene has been studied on the Pt(111) crystal surface by ultraviolet photoelectron spectroscopy (UPS). The adsorptive changes reported in previous studies for carbon monoxide and benzene when potassium is coadsorbed are correlated with the UPS results presented here and are explained with the aid of a molecular orbital analysis. We find that the valence molecular orbitals increase their binding energy slightly when the potassium is coadsorbed, implying a model in which the adsorbates sense the potassium-induced changes in dipole field at the surface.