Showing papers by "Takehiko Sasaki published in 1997"

Oxygen Atoms on Cu(100) Formed at 100 K, Active for CO Oxidation and Water−Hydrogen Abstraction, Characterized by HREELS and TPD

Abstract: The reactivity of oxygen adatoms formed by dissociative adsorption of O2 on Cu(100) at 100 K for CO oxidation and hydrogen abstraction from water was investigated by means of HREELS and TPD in comparison with the reactivity of adsorbed oxygen in thermally stable phases The oxygen adatoms formed on the Cu(100) surface by exposure to O2 at 100 K, designated as as-exposed oxygen, were found to be reactive with coadsorbed CO to yield a CO2 desorption peak at 125 K in TPD The as-exposed oxygen atoms are suggested to be more active for CO oxidation than the oxygen atoms prepared above room temperature on Pt and Pd, which are the most active metals for CO oxidation On annealing the oxygen−as-exposed surfaces to 300 K, a change in the loss feature of ν(Cu−O) was observed, which was indicative of formations of a pseudo c(2×2)-O phase with O(a) in 4-fold hollow sites and a (√2×2√2)R45°-O phase comprised of −Cu−O− chains grown along the [001] direction On these two phases, CO2 formation in TPD was suppressed by

Real Time Observation of Decomposition of Methanol on Ru(001)-p(2 × 2)-O by a Temperature Programmed ESDIAD/TOF System

Abstract: For the purpose of utilizing ESDIAD (Electron Stimulated Desorption Ion Angular Distribution) as a real time probe for surface chemical processes, we have developed a new instrument which can measure ESDIAD images and time of flight (TOF) spectra of desorbed ions in temperature programmed surface processes. TOF measurements are carried out to identify the mass of desorbed ions and to determine their kinetic energy distribution. This temperature-programmed (TP)-ESDIAD/TOF system was used to observe the decomposition processes of methanol on Ru(001)-p(2 × 2)-O. A halo pattern from the methyl group of methoxy species was observed at 100-200 K by the use of CH3OD, followed by a broad pattern from the methyl group at 230-250 K, and by a near-center pattern from the oxygen atom of CO above 300 K.