Long-lived adsorbate states on metal surfaces

It has been shown recently that the peculiarities of the band structure of a metal can qualitatively influence the electron tunnelling between an adso rbate and a metal surface, the so-called resonant charge transfer (RCT). Th e presence of a projected band gap along the normal to the surface in the c ase of Cu(111) has been shown to lead to a blocking of the RCT in the case of Cs/Cu(111), resulting in the existence of a very long-lived excited stat e. Such long-lived states are potentially very important for surface reacti on mechanisms invoking a transient state as an intermediate. Various system s: Cs, model M- negative ion of p pi symmetry, CO adsorbed on Cu(111), are investigated in order to determine the conditions for the blocking of the R CT and the existence of long-lived states.