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  • 1
    Electronic Resource
    Electronic Resource
    Quasielastic helium atom scattering measurements of microscopic diffusion of CO on the Ni(110) surface (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 11297-11304 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microscopic diffusion of CO on the Ni(110) surface has been studied by quasielastic helium atom scattering. From the temperature dependence of the energetic broadening of the quasielastic peak measured at a parallel wave vector near the Brillouin zone boundary, the activation energies for diffusion have been determined to be Ediff=57±4 and 35±4 meV for diffusion parallel to the rows (〈11¯0〉) and perpendicular to the rows (〈001〉), respectively. The activation energies are a factor 2–6 smaller and the preexponential diffusion coefficients orders of magnitude larger than obtained in recent laser measurements of chemical diffusion coefficients, indicating that diffusion over distances from about a few A(ring)ngstroms up to 30 A(ring) is much faster than over the much larger distances probed in macroscopic diffusion measurements. The difference is attributed to the impeding effect of step edges or impurities on the latter measurements. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472983
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The low-energy thermal excitation spectrum of nitrogen molecules adsorbed on Ni(1 1 0): Implications for molecular adsorption sites (1996)
    Springer
    Applied physics 62 (1996), S. 95-101 
    Details
    ISSN: 1432-0630
    Keywords: PACS:  34.50; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  The adsorption of N2 molecules on Ni(110) has been investigated by high-resolution He-atom energy-loss spectroscopy. Two external vibrations in the subthermal (〈30 meV) energy regime at 5.75 and 4.5 meV have been observed and are shown to imply the existence of two different adsorption sites, which are assigned to an on-top and a bridge-site. This finding is at variance with the interpretation of data from electron energy loss spectroscopy and InfraRed (IR) spectroscopy, where only one mode of the internal stretch vibration ν1 at frequencies is observed for the chemisorbed nitrogen molecules. A reanalysis of previously published high-resolution IR data reveals that the presence of the second unexpected adsorbate species correlates with a feature in the IR spectra, which previously has been assigned to N2 molecules adsorbed at defect sites. These findings reveal that in this case the external vibrations are significantly more sensitive to different adsorption sites than the internal vibration, the latter exhibiting a difference between on-top and bridge sites of less than 6 cm-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050272
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The low-energy thermal excitation spectrum of nitrogen molecules adsorbed on Ni(110): Implications for molecular adsorption sites (1996)
    Springer
    Applied physics 62 (1996), S. 95-101 
    Details
    ISSN: 1432-0630
    Keywords: 34.50 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The adsorption of N2 molecules on Ni(110) has been investigated by high-resolution He-atom energy-loss spectroscopy. Two external vibrations in the subthermal (〈 30 meV) energy regime at 5.75 and 4.5 meV have been observed and are shown to imply the existence of two different adsorption sites, which are assigned to an on-top and a bridge-site. This finding is at variance with the interpretation of data from electron energy loss spectroscopy and InfraRed (IR) spectroscopy, where only one mode of the internal stretch vibration v1 at frequencies is observed for the chemisorbed nitrogen molecules. A reanalysis of previously published high-resolution IR data reveals that the presence of the second unexpected adsorbate species correlates with a feature in the IR spectra, which previously has been assigned to N2 molecules adsorbed at defect sites. These findings reveal that in this case the external vibrations are significantly more sensitive to different adsorption sites than the internal vibration, the latter exhibiting a difference between on-top and bridge sites of less than 6 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01575707
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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