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Abstract:
Photoemission studies using XPS and UPS (HeI, HeII) on clean and gas-covered hexagonal (0001)-Cobalt-single-crystal surfaces are reported (300 K). To interpret the results on the adsorbates namely Co/CO and Co/O2 , compound systems, such as CoO, Co3 O4 and Co2 (CO)8 are studied parallel and comparison is made. It is shown that the emission from Co/O2 is similar to that from CoO and not to that from Co3 O4 and that the Co/CO-systems resembles the Co2 (CO)8-photoemission characteristics. Assignment of CO-peaks as far as the sequence of the 4σ, 1π and 5σ is concerned is shown to be the same as in free CO. The C1s spectrum of the carbonyl is analysed using theoretical predictions of atomic populations, which show the bridging ligands to carry more electron density than terminal ones. From comparison with adsorbate systems it follows that the differences in the adsorbate system are not as pronounced as in the case of the carbonyls.
