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O: Oberflächenphysik
O 26: Adsorption an Oberflächen II
O 26.7: Vortrag
Dienstag, 9. März 2004, 17:15–17:30, H45
Adsorption of CO on the ( 1010 ) surface of Rhenium — •C. Pauls, D. Przyrembel, and K. Christmann — Inst. f. Chemie, FU Berlin, Takustr. 3, 14195 Berlin
We have performed LEED, thermal desorption (TD), and work function change ( Δ Φ ) measurements of CO interacting with the ’open’ Re( 1010 ) surface. Upon exposure at 200 K, negatively polarised ( Δ Φ ≈ 780 meV) molecular α states are populated. TD spectra reveal these states between 250 and 400 K ( Edes = 95...118 kJ/Mol) and, in addition, pronounced β states due to dissociated CO between 600 and 800 K. Direct CO exposure at 500 K exclusively yields dissociated CO as evidenced by i) 2nd order desorption kinetics at low coverages ( Edes = 207 kJ/Mol) and ii) the formation of a p(1x2) LEED phase at a CO coverage of Θ = 0.25. carbon]. Between 0.125 and 0.16 ML an additional c(2x4) phase appears. During desorption, both phases undergo an order-disorder transition. In the coverage range of the p(1x2) phase the respective TD spectra show a common leading edge (zero-order kinetics) until the critical temperatur of ∼ 660 K is reached.