Comparative Study of Angle Resolved Valence Band Photoemission from Half-monolayer Structure of C, N and O on Ni(100).

Angle-resolved synchrotron radiation photoemission has been used to map the adsorbate-induced surface valence bands of the simple chemisorbed Ni(100) c(2x2)-O structure and the reconstructed Ni(100)(2x2)-N structure; the results are compared with a similar previous study of the reconstructed Ni(100)(2x2)-C structure. The oxygen adsorption system shows three 2p-derived bands broadly in agreement with early calculations by Leibsch although the splitting of the p sub z and p sub x, p sub y bands at GAMMA bar is revealed convincingly only in data taken in the second surface Brillouin zone and folded back to the zone centre; at normal emission on Ni(100) substrate emission confuses the interpretation.