Observation of a fano resonance in photoemission

Abstract

We report on the observation of a Fano resonance in normal emission ultraviolet photoelectron spectra of Cu or Ag impurities embedded in a Xe monolayer on highly oriented pyrolytic graphite. We show that Brillouin-zone folding resulting from the relatively weak perturbation by the (√3 × √ 3)R30° commensurate Xe overlayer couples K-point electrons with G-point electrons of pure graphite. Interference between this continuum of states and the discrete Cu 4s or Ag 5s states in the initial state leads to a typical Fano line profile in the spectra. This finding provides a new and promising avenue for the detection and characterization of impurities or small clusters at surfaces. © 1999 The American Physical Society.