CHEMISORPTION OF NO ON PT(210) STUDIED BY UPS, XPS AND AES

The chemisorption of NO on the Pt(210) surface has been studied by pho toelectron spectroscopy (UPS and XPS) and Auger electron spectroscopy (AES). The UPS results show that NO molecular orbitals appear at 2.8, 9.6, 11.3 and 14.8 eV below the Fermi level after full coverage of NO on the Pt(210) surface at room temperature. These molecular orbitals o riginate from 2pi, 1pi, 5sigma and 4sigma, respectively. The peak from the 1pi orbital shifts to the lower binding energy side by 0.6 eV wit h increasing temperature. The molecular levels disappear at around 450 K. The energy shift of the 1pi orbital is caused by the increase of t he N-O bond length, which correlates with the change of adsorption sta te of NO; that is, from the terminal sites to the bridge sites.The dis appearance temperature of the NO molecular orbitals, T(D), and the dec reasing temperature of the N(KLL) Auger electron intensity, T(A), corr elate with the surface activity for NO decomposition. From the UPS and AES results for the Pt surfaces, the order of activity for the NO dec omposition is as follows: (410) > (310) > (100) > (210) > (110).