Observation of an sp-derived surface resonance on Pt(111) indicating the crucial role of surface states in physisorption

High-resolution angle-resolved photoemission of Pt(111) reveals the presence of an sp-derived surface resonance close to EF in the centre of the surface Brillouin zone. Similar surface states are found on all (111) faces of the d9 transition and the noble metals with the only exception of Pd(111). This finding is used to explain previous observations of an exceptional physisorption behaviour of Pd(111) towards Xe and H2. The results strongly suggest that surface states crucially influence the physisorption potential on metal surfaces.