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  • 1
    Electronic Resource
    Electronic Resource
    Electron stimulated desorption of NO from step sites on Pt(112): The role of chemisorption site geometry on the cross section (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3925-3929 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic excitation of adsorbed NO on Pt(112) has been observed to cause mainly desorption. Species-specific total desorption cross sections of terminally bound and bridged-bound NO present exclusively on the step sites of Pt(112) have been measured using Fourier transform infrared reflection absorption spectroscopy (FT-IRAS) as a sensitive detector of the surface coverage of various chemisorbed NO species. Other electron stimulated processes which might influence the measurement of these cross sections, such as electron stimulated fragmentation, site-exchange, and occupied site density effects have been found to be unimportant. It was found for 275 eV electrons that terminally bound NO desorbs with a larger cross section (2.3×10−18 cm2) than bridged-bound NO, which has a desorption cross section of 8.7×10−19 cm2. This is the expected relationship between the total desorption cross sections for these two species, with the smaller cross section being observed for the bridged NO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466327
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  • 2
    Electronic Resource
    Electronic Resource
    CO Chemisorption on Monodispersed Platinum Clusters on SiO2: Detection of CO Chemisorption on Single Platinum Atoms (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 8730-8735 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100021a044
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  • 3
    Electronic Resource
    Electronic Resource
    NO electronic desorption processes from step sites on Pt(112): A comparison between photo- and electron-stimulated desorption (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4373-4378 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using Fourier-transform infrared reflectance absorption spectroscopy as a surface analytical method, the total photo- and electron-stimulated desorption cross sections for specific chemisorbed NO species on the steps of Pt(112) have been measured. These species-specific cross sections for photo- and electron stimulated desorption are compared with each other. An unexpected result was obtained for photo-stimulated desorption, using photons with an energy of 3.5 eV; bridged-NO desorbs with a higher cross section (1.1×10−22 cm2) than terminal-NO (6.1×10−23 cm2). For electron stimulated desorption, using electrons of an energy of 275 eV, the opposite is observed. Terminal-NO desorbs with a higher cross section (2.3×10−18 cm2) than bridged-NO, with a cross section of 8.7×10−19 cm2. The photo-stimulated process is discussed within the "hot electron'' model, and it is postulated that the higher expected quenching rate of the NO−(a) species produced from the more strongly-bound bridged-NO is more than compensated by propagation of the short-lived intermediate NO−(a) toward the metal surface. This leads to a closer approach to the surface of NO−(a) produced from bridged-NO than from terminal-NO, giving a higher probability of photodesorption of bridged-NO compared to terminal-NO. For the bridged-NO species, this is due to a steeper slope of the NO−(a) potential energy surface at the Franck–Condon excitation point compared to the slope for the terminal-NO which is initially located further from the surface. Electron stimulated desorption yields the expected relationship between the total desorption cross section for bridged- and terminal-NO, with the more strongly-bound bridged-NO having the smaller cross section. Here it is postulated that bridged- and terminal-NO connect to highly-excited NO states which do not differ so much in their dynamical interaction with the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467488
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  • 4
    Electronic Resource
    Electronic Resource
    Phosphine chemistry on molybdenum (110) and oxidized molybdenum (110) (1993)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 5074-5079 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100121a038
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical reactivity of size-selected supported clusters: An experimental setup (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1986-1994 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe an experimental setup for the investigation of the chemical reactivity of size-selected, supported clusters. The clusters are generated by a high frequency laser vaporization source. After mass selection and energy control the clusters are deposited under ultrahigh-vacuum conditions and with low kinetic energy onto thin oxide films grown on metal single crystals. Such films are ideal in their function as supports for size-selected deposited metal clusters. Measured currents of mass-selected niobium cluster ions were of the order of 1 nA and are high enough for fast deposition rates. Adsorbed molecules used on the one hand as probes to characterize the supported clusters and on the other hand for studying chemical reactions on these clusters are investigated in situ by Fourier transform infrared spectroscopy, temperature desorption spectroscopy, and Auger electron spectroscopy. The performance of these analytical tools is illustrated with CO adsorbed on Ni atoms supported on thin MgO(100) films grown on a Mo(100) single crystal. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148113
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  • 6
    Electronic Resource
    Electronic Resource
    A new cluster source for the generation of binary metal clusters (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3718-3722 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new thermal, supersonic cluster source for the investigation of binary metal cluster formation at thermodynamically well-defined expansion conditions is described. The source consists of two separately heatable cartridges. A first cartridge can be heated up to 1220 K and the second high temperature cartridge reaches maximal temperatures of 1800 K. A temperature difference of 1000 K between the two cartridges can be maintained for at least 3 h. Clustering occurs upon supersonic expansion from a conical nozzle. This cluster source has two main applications: (a) the generation of mixed metal clusters and (b) the investigation of pure metal clusters at various expansion conditions. The performance and applications of this source are illustrated by presenting results of the heterocluster formation of mixed sodium/gold and sodium/silver heteroexpansions. In addition, the influence of the oven parameters on the internal temperatures of the generated clusters is illustrated with the example of Na2. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148015
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  • 7
    Electronic Resource
    Electronic Resource
    Size-selected, supported clusters: the interaction of carbon monoxide with nickel clusters (1998)
    Springer
    Applied physics 67 (1998), S. 621-626 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 36.40.Jn; 33.20.Ea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We report on the size-dependent chemical reactivity of nickel clusters with up to 30 atoms. Monodispersed Ni30 clusters show a higher reactivity for CO dissociation than Ni11 and Ni20. Under our experimental conditions the smallest nickel clusters (Nix, x〈4) produce nickelcarbonyl complexes. These results demonstrate that such small clusters are unique for catalytic reactions not only due to their high surface-to-volume ratio but also essentially because of the distinctive properties of different cluster sizes. In addition thermal desorption spectroscopy of CO shows that on average four molecules are weakly adsorbed per Ni11 at saturation coverage. Using an isotopic mixture of 12CO and 13CO, infrared spectroscopy reveals the existence of a vibrational coupling interaction between the four COs. A semi-classical model of interacting dipoles is applied to correlate the observed vibrational frequency shifts with the arrangement of the COs on the cluster. This simple analysis favors a three-dimensional structure for the deposited clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050833
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  • 8
    Electronic Resource
    Electronic Resource
    The reactivity of gold and platinum metals in their cluster phase (1999)
    Springer
    The European physical journal 9 (1999), S. 35-39 
    Details
    ISSN: 1434-6079
    Keywords: PACS: 36.40.Jn Reactivity of clusters – 82.65.Jv Heterogeneous catalysis at surfaces – 82.80.Ch Ultraviolet, visible, infrared, Raman, microwave, and magnetic resonance spectroscopic analysis methods, spectrophotometry; colorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Platinum surfaces are known to be among the most active ones for the oxidation of carbon monoxide, whereas gold surfaces are completely inert for this reaction. The question remains: Do small clusters of these two metals maintain these distinct differences? To answer this question, we have employed temperature-programmed reaction (TPR) and Fourier transform infrared (FTIR) spectroscopy to investigate the reactivity of small platinum and gold clusters consisting of up to 20 atoms. These clusters are generated in the gas phase by a laser evaporation source and, after mass selection, are deposited with low kinetic energy onto thin MgO films. The oxidation of CO is studied for the octamer and the icosamer under UHV conditions. Surprisingly, all investigated cluster sizes are catalytically active. Pt20 shows the highest reactivity and oxidizes almost 6 CO molecules, whereas Pt8, Au20, and Au8 oxidize just one CO molecule under identical experimental conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050395
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  • 9
    Electronic Resource
    Electronic Resource
    Size-dependent light emission from mass-selected clusters (1998)
    Springer
    The European physical journal 2 (1998), S. 79-82 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 32.50.+d Fluorescence, phosphorescence (including quenching)[:AND:] 36.40.-c Atomic and molecular clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The emission of photons in the visible wavelength range from mass-selected Ag+ n, Cu+ n, Pt+ n and Pd+ n ( ) clusters is observed. Photons are detected 10-4 s after the cluster generation in a sputter source. The emission intensities display distinct variations with cluster size and material. The observations are interpreted in terms of the decay of metastable states which are excited during the high-energy sputtering process used for the generation of these clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050114
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  • 10
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    Cavity ring-down spectrometer for measuring the optical response of supported size-selected clusters and surface defects in ultrahigh vacuum (2008)
    American Institute of Physics
    Details
    Publication Date: 2008-12-15
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics
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