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Helmut Klapper, H. F. Kempin, Gerhard Ertl
Field Emission Spectroscopy from Clean and Adsorbate Covered Iridium Surfaces
Keywords: FEED, 127°-Analyzer, (111) surface, Co, oxygen chemisorption
FEED / 127 -Analyzer / (111) Staface / CO I Oxygen chen1isorption Field emission energy distribution (FEED) spectra from clean and adsorbate covered Ir surfaces were recorded by means of a newly designed analyzer system in which a KuyattSimpson type lens system is combined with a two-stage 127°-analyzer. Emission from clean (100), (110), (210), and ("113) planes obeys well the behavior of a free-electron gas model. The clean (111) surface exhibits a marked maximum of the enhancement factor at 0.5 eV below the Fermi level which corresponds with a high density of s-like states in the theoretical band structure. Adsorption ofCO on Ir (100) causes the formation ofa maximum at - 0.6 eV which is identified with a chemisorption level arising from coupling some metallic d-states with the antibonding 2π*-level of CO ("back-donation" effect). After oxygen chemisorption on Ir (100) and (110) a broad maximum centered at -1.0 eV was observed which is ascribed to a state derived from one of the 02p-levels.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 112, 01/1978
Pages: 045 - 057