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The adsorption of oxygen and the interaction of carbon monoxide with oxygen on Ru(101) have been studied by LEED, Auger spectroscopy and thermal desorption. Oxygen chemisorbs at 300 K via a precursor state and with an initial sticking probability of ~0.004, the enthalpy of adsorption being ~300 kJ mol?1. As coverage increases a well ordered ¦11,30¦ phase is formed which at higher coverages undergoes compression along [010] to form a ¦21,50¦ structure, and the surface eventually saturates at 0 ~ . Incorporation of oxygen into the subsurface region of the crystal leads to drastic changes in the surface chemistry of CO. A new high; temperature peak (γ CO, Ed ~ 800 kJ mol?1) appears in the desorption spectra, in addition to the α and β CO peaks which are characteristic of the clean surface. Coadsorption experiments using 18O2 indicate that γ CO is not dissociatively adsorbed, and this species is also shown to be in competition with β CO for a common adsorption site. The unusual temperature dependence of the LEED intensities of the ¦11,30¦-O phase and the nature of α, β, and β CO are discussed. Oxygen does not displace adsorbed CO at 300 K and the converse is also true, neither do any Eley-Rideal or Langmuir-Hinshelwood reactions occur under these conditions. Such processes do occur at higher temperatures, and in particular the reaction CO(g) + O(a) → CO2(g) appears to occur with much greater collisional efficiency than on Ru(001). The oxidation of CO has been examined under steady state conditions, and the reaction was found to proceed with an apparent activation energy of 39 kJ mol?. This result rules out the commonly accepted explanation that CO desorption is rate determining, and is compared with the findings of other authors. 相似文献
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Falepin A. Cottenier S. Comrie C. M. Richard O. Bender H. Langouche G. Vantomme A. 《Hyperfine Interactions》2003,151(1-4):131-144
Hyperfine Interactions - The phase formation and crystallization processes of metastable [CsCl]Fe1?x Si phases were investigated by irradiating?-FeSi/Si(111) thin films with a pulsed... 相似文献
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Pulsed laser annealing has been applied on ε-FeSi layers in order to study the formation of (meta)stable iron silicides. Laser shots of different energy density were applied and/or the number of laser shots was also varied. Characterisation was performed using Rutherford Backscattering Spectroscopy (RBS)/Channelling and Conversion Electron Mössbauer Spectroscopy (CEMS). The reaction mechanisms of the Fe/Si system as well as the stability of the phases are discussed. 相似文献
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