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  • 1
    Electronic Resource
    Electronic Resource
    The trapping of methane on ordered structures of CO on Pt(111) (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 838-847 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of methane trapping on CO-covered Pt(111) in low coverage, c((square root of)3×5)rect, and c(4×2) structures was investigated using supersonic molecular beam techniques at a surface temperature of 50 K; at this temperature methane was stably adsorbed on the clean (A. F. Carlsson and R. J. Madix, to be published) surface, but not in multilayers (A. F. Carlsson and R. J. Madix, to be published), and thus trapped amidst adsorbed CO molecules. Molecular trapping was enhanced to greater degrees with increasing CO coverage, and the methane uptake decreased with increasing CO coverage, as would be expected. The trapping probability further increased as methane covered the Pt(111)–CO surface; the modified Kisliuk model [J. Chem. Phys. 92, 1397 (1990); J. Phys. Chem. 95, 2461 (1991)] describes the coverage-dependent trapping probability. Methane adsorption may occur directly on the surface, or via two entrance channels into an extrinsic precursor, where the trapping probability is higher. The angular dependence of methane trapping on the CO-covered surface suggests an increasing corrugation in the gas–surface potential as the CO coverage increases; the corrugation may also contribute to the enhancement of the overall trapping probability by facilitating interconversion of perpendicular to parallel momentum during the gas–surface collision. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481859
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  • 2
    Electronic Resource
    Electronic Resource
    The dynamics of ethylene adsorption on Pt(111) into di-σ and π-bonded states (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 8074-8082 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of ethylene adsorption on Pt(111) into both the di-σ- and π-bonded states were investigated at 95 and 40 K, respectively, using supersonic molecular beam techniques. The angular dependence of ethylene adsorption into both states is similar to the angular dependence for ethane adsorption, which has a much weaker bond to the surface in its final state. In contrast to ethane, high adsorption probabilities for ethylene prevail to high incident kinetic energies, suggesting that the strong interaction of ethylene with the surface influences adsorption. The initial adsorption probability of ethylene is approximately independent of surface temperature between 40 and 450 K, suggesting that there is no reversible, thermalized intrinsic precursor to adsorption. At 40 K, the adsorption probability increases with coverage (in the π-bonded state). However, at 95 K, the adsorption probability of ethylene remains constant with increasing self-coverage (in the di-σ- bonded state) for trajectories incident with low parallel momentum, but decreases with coverage at high parallel momentum. High parallel momentum may contribute to an increased overall scattering probability from a "hot" extrinsic precursor, resulting in a decreased net adsorption probability at higher ethylene coverage in the rigidly bound di-σ state. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1380373
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  • 3
    Electronic Resource
    Electronic Resource
    Intrinsic and extrinsic precursors to adsorption: Coverage and temperature dependence of Kr adsorption on Pt(111) (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 5304-5312 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The kinetics of krypton adsorption on Pt(111) were investigated using supersonic molecular beam techniques. Krypton adsorbs at defects via an intrinsic precursor below a surface temperature of 85 K. The difference in activation energies for desorption and migration of a Kr atom on the terrace seeking a defect site is 10.7 kJ/mol, indicating that at 80 K, a Kr atom makes about 107 site hops before desorbing or finding a binding site. Below 60 K stable adsorption occurs on terraces, where the initial adsorption probability is independent of surface temperature. The activation energy for zero-order desorption from Pt(111) terraces is 12.9 kJ/mol; the activation energy for Kr migration on the terraces is then calculated to be ≤2.2 kJ/mol. Krypton adsorption proceeds at nonzero coverages via an extrinsic precursor. The adsorption probability of Kr increases with self-coverage, and is described by the modified Kisliuk model [H. C. Kang, C. B. Mullins, and W. H. Weinberg, J. Chem. Phys. 92, 1397 (1990); C. R. Arumainayagam, M. C. McMaster, and R. J. Madix, J. Phys. Chem. 95, 2461 (1991)]. The Kr overlayer on terraces compresses between 60 and 42 K, then forms a second state before forming stable multilayers at 34 K. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1350816
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    Paper (German National Licenses)
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