Cu(100) surfaces

~538 The interaction of methane, propane, ethene and propene with clean and oxidised Cu(111) has been studied in the temperature range 300-750 K and at pressures up to 0 1 Pa with elhpsometry, AES and LEED Methane and propane showed no measurable Interaction under our condmons Propene exposure on Cu(111) at T > 475 K resulted in a slow carbon deposmon of the graphlt~C type Propene was able to remove all oxygen from C u ( l l l ) / O at T> 625 K The fastest part of the reductmn has a first order dependence on the propene pressure, the apparent activation energy is 44 9 + 5 2 kJ mol- 1 Though ethene is less reactwe than propene tt is also able to reduce an oradlsed copper surface at T = 725 K

Surface Science 290 (1993) 309-318 North-Holland

XPS and XAES study for oxidation of V/Cu(100) and V,Na/Cu(100) surfaces Kosaku Kishl, Katsunorl Hlral and Tatsuro Yarnamoto Department of Chermstry, School of Science, Kwanse: Galaan Umversity, N~anormya, Hyogo 662, Japan Recewed 19 November 1992, accepted for pubhcatlon 3 March 1993 Oyadatmn states of vanadium overlayers ( ~ 0 1 to 2 0 ML) on a Cu(100) surface with and w~thout sochum on the surface were investigated by XPS and XAF_~ The vanadium overlayers gave a V203-hke surface orade after exposure up to 600 L 0 2, showing a chemical shift of the V 21:)3/2 peak by 3 5 eV without coverage dependence The surface vanadmm oxide was easdy oxidized further to V 5+ to give a chemical shift of 5 5 eV after addmon of sochum atoms on the oyade and heating at 530 K for 5 mm The high oxidaUon state was interpreted by a mtrang of vanadium orade and oxidized sodmm This mvang is affirmed by spectral changes showing a separatmn of sodium Ions from the oyade during the formatmn of sodmrn acetate by adsorption of aeeuc acid

Surface Science 290 (1993) 319-334 North-Holland

Reactions of rr-allyl with atomic oxygen and hydroxyl on Ag(ll0) Robert N Carter, A Brad Anton School of Chemical Engmeenng, Cornell University, Ithaca, NY 14853-5201, USA

and G Apal Corporate Research Laboratories, Eastman Kodak Company, Rochester, NY 14650-2001, USA Re~etved 1 September 1992, accepted for pubhcatmn 19 February 1993 The predation of the adsorbed ¢r-allyl ('r/3-C3H5), prepared on atomic oxygen- and hydroxyl-covered Ag(ll0) by dlssoclaUon of allyl chloride (C3H5C1), is investigated with temperature-programmed desorptton and h~h-resoluUon electron energy loss spectroscopy Allyl chloride adsorbs molecularly on oxygen-covered Ag(ll0) at 110 K Upon heating to 180 K, some allyl chloride dissociates to form ¢r-allyl and atomic chlorine, and the remainder desorbs molecularly The ¢r-allyl undergoes combusnon to form hydroxyl or carbonate until all of the free oxygen is consumed by 200 K Migratory insertion of hydroxyl into excess ¢r-allyl commences near 220 and finishes by 250 K, forming adsorbed ailyl alcohol (C3HsOH), which reacts either with excess hydroxyl near 240 K to form allyl aikoxy ('r/I(O)-C3H50) and water, or with ~r-allyl at 250 K to form allyl aikoxy and propylene (C~H6) The aJlyl alkoxT evolves acrolem (C3H40) by /3-hydrogen ehmlnation near 285 K, and propylene is evolved concurrently as the hydrogen released by this reactmn rapidly scavenges ~r-allyl Finally, the remaining ~--allyl dlmerizes to form 1,5-hexadlene (C6H~0), which desorbs at 315 K. The gross observations of reaction pathways and temperatures are used to evaluate ~mportant aspects of the thermochemistry of these reaeUons