title: Pi resonance of chemisorbed alkali atoms on noble metals.
abstract: We have performed a joint experimental and theoretical study of the unoccupied electronic structure of alkali adsorbates on the (111) surfaces of Cu and Ag. Combining angle- and time-resolved two-photon photoemission spectroscopy with wave packet propagation calculations we show that, along with the well known sigma resonance oriented along the surface normal, there exist long-lived alkali-localized resonances oriented parallel to the surface (pi symmetry). These new resonances are stabilized by the projected band gap of the substrate and emerge primarily from the mixing of the p and d Rydberg orbitals of the free alkali atom modified by the interaction with the surface.
authors.affiliation: Laboratoire des Collisions Atomiques et Moléculaires, UMR CNRS-Universite Paris-Sud 8625, Bâtiment 351, Université Paris-Sud, 91405 Orsay cedex, France. andrei.borissov@u-psud.fr
authors.forename: A G
authors.initials: AG
authors.lastname: Borisov
authors.forename: V
authors.initials: V
authors.lastname: Sametoglu
authors.forename: A
authors.initials: A
authors.lastname: Winkelmann
authors.forename: A
authors.initials: A
authors.lastname: Kubo
authors.forename: N
authors.initials: N
authors.lastname: Pontius
authors.forename: J
authors.initials: J
authors.lastname: Zhao
authors.forename: V M
authors.initials: VM
authors.lastname: Silkin
authors.forename: J P
authors.initials: JP
authors.lastname: Gauyacq
authors.forename: E V
authors.initials: EV
authors.lastname: Chulkov
authors.forename: P M
authors.initials: PM
authors.lastname: Echenique
authors.forename: H
authors.initials: H
authors.lastname: Petek