Nature of the Excited States of Rare-Gas Atoms Adsorbed on Metal Surfaces

Electron energy-loss spectroscopy has been used to study the coverage-dependent, electronic excitations of Ar and Xe adsorbed on Al(111), Ag(111), Cu, and Au surfaces. The monolayer loss features and cross sections indicate broadened atomiclike excitations with no evidence for a configurational-switching effect suggested in previous optical studies. The np⁵(n+1)s excited-state lifetime is found to be {~}4 times longer than theoretically predicted for isolated adatoms.