Münster 1997 – scientific programme
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O: Oberflächenphysik
O 25: CO-Adsorption
O 25.12: Talk
Wednesday, March 19, 1997, 18:45–19:00, S 2
NON-REACTIVE COADSORPTION OF CO AND OXYGEN ON IR(110) — •U. Burghaus, Junqi Ding, and W.H. Weinberg — UC Santa Barbara, Dept.Chem.Eng.II, CA 93106-5080, USA
“Non-reactive” sticking measurements of CO on clean and oxygen precovered Ir(110) by means of the molecular beam reflectivity method are reported. Impact energy Ei and angle, surface temperature Ts, and oxygen precoverage θO were varied. For the clean surface, S0 is independent of Ts (85-300 K) and decreases linearly with increasing Ei. The shape of S(θCO) points to precursor-mediated adsorption kinetics for 1 < Ei < 25 kcal/mol. A pronounced decrease of S0(θO) with increasing θO is observed for Ei > 3 kcal/mol. However, for Ei < 3 kcal/mol S0(θO) remains constant at 0.90 ± 0.03. The results suggests that the influence of θO on S0 can be explained by a pure physical site-blocking mechanism. The increase of S0 for decreasing θO may introduce an “autocatalytic” component into CO2 formation rate for Ts > 300 K.