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Orientation and substrate interaction of adsorbed CO and NO molecules probed by circular dichroism in the angular distribution of photoelectrons

1994; American Physical Society; Volume: 50; Issue: 23 Linguagem: Inglês

10.1103/physrevb.50.17534

1095-3795

C. Westphal, F. Fegel, Joachim Bansmann, M. Getzlaff, G. Schönhense, J. A. Stephens, Vincent McKoy,

Catalytic Processes in Materials Science

The sensitivity and utility of circular dichroism in the angular distribution of photoelectrons (CDAD) as a probe of molecular orientation is demonstrated for adsorbed CO and NO molecules. A comparison between measured CDAD spectra and calculated values for spatially oriented CO and NiCO clearly confirms the well-known perpendicular adsorption for CO on Ni(100), whereas for CO adsorbed on Fe(100) a tilted adsorption geometry was found. For NO/Ni(100) and for NO on the oxygen-preadsorbed Ni(100) surface, an average tilt angle of \ensuremath{\alpha}=40\ifmmode\pm\else\textpm\fi{}10\ifmmode^\circ\else\textdegree\fi{} was observed. In the case of the oxygen-preadsorbed Ni(100) surface, a higher fraction of NO molecules was found to be in a tilted orientation than on the clean surface.