Angle-resolved photoemission studies of oxygen adsorbed on Fe(100)

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Abstract
A (1×1) overlayer of segregated oxygen on Fe(100) was investigated by means of angle-resolved ultraviolet photoelectron spectroscopy with use of polarized synchrotron radiation. Distinct photoemission peaks arise from the oxygen 2p levels in the region of 4.0 to 8.5 eV initial-state binding energy. Odd and even bands are distinguished in the Γ¯ X¯ and Γ¯ M¯ crystal directions by use of symmetry selection rules. The odd states qualitatively follow tight-binding calculations, whereas the even states hybridize with the iron conduction band. Hybridization of even oxygen bands leads to an energy gap of 0.5 eV in the Γ¯ X¯ direction. In the Γ¯ M¯ direction, no hybridization gap exists. The experimental results are discussed on the basis of tight-binding and cluster-model calculations.