NEXAFS and XPS characterization of molecular oxygen adsorbed on Ni(100) at 80 K

X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS) and near edge extended X-ray absorption fine structure (NEXAFS) have been combined to investigate the adsorption of oxygen on Ni(100) at 80 K. Three O(1s) XPS features were observed at 530.0, 531.1 and 534.7 eV when the Ni(100) surface was exposed to 600 L of oxygen at 80 K. They are assigned as O2-, O1- and molecular oxygen species, respectively. The presence of molecular oxygen has been confirmed by TDS and NEXAFS. Molecular O-2 on Ni(100) is oriented perpendicular to the surface, and the O-O bond length is estimated to be 1.24 Angstrom, based on the NEXAFS sigma* resonance energy. (C) 2000 Published by Elsevier Science B.V. All rights reserved.