Adsorbate{endash}adsorbate repulsions{emdash}the coverage dependence of the adsorption structure of CO on Cu(110) as studied by electron-stimulated desorption ion angular distribution

Journal Article · Tue Oct 01 04:00:00 EDT 1996 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.472464· OSTI ID:385647

Ahner, J ^[1]; Mocuta, D; Ramsier, R D ^[2]; Yates, Jr, J T ^[1]

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1. Department of Chemistry, University of Pittsburgh, Surface Science Center, Pittsburgh, Pennsylvania 15260 (United States)
2. Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

The coverage dependent orientation of CO adsorbed on a Cu(110) surface was studied by the electron-stimulated desorption ion angular distribution (ESDIAD) technique. A neutral excited (CO{asterisk}) species is imaged and in addition positive ions are measured. The adsorption temperature was varied between 32 K and 150 K. By applying the ESDIAD technique at a temperature below 80 K it was possible to decrease the beamwidths drastically, to determine the angular distributions better than {plus_minus}0.5{degree}, and to study the adsorption of CO chemisorbed and physisorbed on the surface. With increasing CO coverage we observe three distinct ESDIAD patterns. Starting from a normal beam pattern with an elliptical cross section with the major axis oriented in the {l_angle}1{bar 1}0{r_angle} direction for coverages up to 0.2 monolayer (ML), a transformation of the ESDIAD pattern into a pattern of two separated beams is observed for a coverage of about 0.5 ML, indicating a tilting of the molecules in the {l_angle}1{bar 1}0{r_angle} directions by {approximately}9{degree}. With further increasing CO coverage an additional central peak develops with an elliptical broadening now in the {l_angle}001{r_angle} direction. The changes of the pattern are reversible as shown by decreasing the coverage by thermal desorption. Based on these ESDIAD and digital low energy electron diffraction results, a linear-chain model for CO adsorption is proposed. Temperature programmed desorption measurements also indicate the presence of repulsive CO{endash}CO interactions in the adlayer. {copyright} {ital 1996 American Institute of Physics.}

• OSTI ID: 385647
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 15 Vol. 105; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ANGULAR DISTRIBUTION
CARBON MONOXIDE
CHEMISORPTION
COPPER
CROSS SECTIONS
ELECTRON DIFFRACTION
ELECTRON STIMULATED DESORPTION
LINE BROADENING
TEMPERATURE DEPENDENCE