Photon-induced desorption of CO chemisorbed on the oxidized Ni(111) surface

Abstract

Photon-induced desorption studies of chemisorbed CO on Ni(111), Ni(111) with chemisorbed oxygen, and oxidized Ni(111) surfaces have been carried out. Only the oxidized Ni(111) surface exhibits measurable CO photodesorption in the energy range from 1.8 to 4.1 eV. Both direct observation of CO photodesorption and post-irradiation thermal desorption of CO have been performed. The photodesorption process is first order in photon flux and in CO coverage. At a photon energy of 4.1 eV, the cross section for CO photodesorption is measured to be 5×10−18 cm2. The measured threshold energy, 2.7±0.5 eV, is in good agreement with a model involving the O2−2p→Ni2+3d interband transition in NiO as the excitation process leading to photodesorption.