Broadening mechanisms for the adsorbate-induced resonance in the Na/Cu(1 1 1) and Cs/Cu(1 1 1) systems |
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Authors: | A.K. Kazansky A.G. Borisov |
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Affiliation: | a Fock Institute of Physics, St. Petersburg State University, St. Petersburg 198504, Russia b Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal 4, 200018 San Sebastián/Donostia, Basque Country, Spain c Laboratoire des Collisions Atomiques et Moléculaires, UMR CNRS-Université Paris-Sud 8625, Bât. 351, Université Paris-Sud, 91405 Orsay Cedex, France |
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Abstract: | Adsorption of alkali atoms on the (1 1 1) and (1 0 0) noble metal surfaces has been shown recently to induce long-lived resonances located inside the surface projected band gap. However, the width of these resonances, as it appears in two-photon photo-emission experiments, is much larger than the inverse of their lifetime. We report on a theoretical study of some broadening mechanisms of these resonance lines in the Na/Cu(1 1 1) and Cs/Cu(1 1 1) systems at low coverage, including the homogeneous natural line broadening and the inhomogeneous statistical broadenings due to the distribution of adsorption heights associated to the quantal vibration of the alkali adsorbate and to the lateral disorder of alkali adsorption on the surface. The inhomogeneous mechanisms are shown to induce a very large broadening of the resonance line, in quantitative agreement with experimental results. The most important broadening effect appears to be the effect of the distribution of alkali adsorption heights. |
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Keywords: | Surface electronic phenomena Photo-electron emission Metallic surface Copper Alkalis Adatoms |
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