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  • 1
    Electronic Resource
    Electronic Resource
    Interaction of gaseous D atoms with alkyl halides adsorbed on Pt(111), H/Pt(111), and C/Pt(111) surfaces: Hot-atom and Eley–Rideal reactions. I. Methyl bromide (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 3209-3217 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The interaction of gaseous D atoms with methyl bromide molecules adsorbed on Pt(111), hydrogen saturated Pt(111), and graphite monolayer covered Pt(111) surfaces was studied in order to elucidate the reaction mechanisms. The reaction kinetics at 85 K surface temperature were measured as a function of the methyl bromide precoverage by monitoring reaction products simultaneously with D atom exposure. On all substrates incoming atoms abstract the methyl group from adsorbed CH3Br via gaseous CH3D formation. In the monolayer regime of CH3Br/Pt(111) pure hot-atom phenomenology was observed in the rates. At multilayer targets the fluence dependence of the kinetics gets Eley–Rideal-like. With coadsorbed H present, the reaction of D with adsorbed methyl bromide revealed in addition to CH3D a CH4 product. This and simultaneous abstraction of adsorbed H via gaseous HD and H2 products clearly demonstrates that hot-atom reactions occur. At CH3Br adsorbed on a graphite monolayer on Pt(111) the abstraction kinetics of methyl was found to agree with the operation of an Eley–Rideal mechanism. These observations are in line with the expectation that hot-atoms do not exist on a C/Pt(111) surface but on Pt(111) and H/Pt(111) surfaces. The methyl abstraction cross-sections in the monolayer regime of methyl bromide were determined as about 0.25 Å2, irrespective of the nature of the substrate. This value is in accordance with direct, Eley–Rideal or hot-atom reactions. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479600
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  • 2
    Electronic Resource
    Electronic Resource
    Interaction of gaseous D atoms with alkyl halides adsorbed on Pt(111), H/Pt(111), and C/Pt(111) surfaces: Hot-atom and Eley–Rideal reactions. III. Isopropyl iodide (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 3225-3232 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The kinetics of reactions of D atoms with isopropyl iodide adsorbed on Pt(111), H covered Pt(111), and monolayer C covered Pt(111) surfaces were studied using direct product detection. Propane, C3H7D, was observed as gaseous product formed through propyl abstraction from the halide. At low temperatures, below the propane desorption temperature, and submonolayer coverages the reaction products remain adsorbed on the surface. At higher temperatures (coverages) they desorb. With C/Pt(111) as substrate, the reaction kinetics are compatible with the operation of an Eley–Rideal mechanism. On Pt(111) and H/Pt(111) substrates the abstraction kinetics of propyl from the halide is controlled by hot-atom mechanisms. Coadsorbed H leads to simultaneous abstraction of H from the surface towards HD and H2, as well as to a gaseous C3H8 product. Propyl abstraction cross-sections are in the range 0.5 to 1.5 Å2, in line with direct processes. The results confirm the role of a metallic or nonmetallic substrate on the mechanisms of atom–adsorbate reactions. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479602
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  • 3
    Electronic Resource
    Electronic Resource
    Interaction of gaseous D atoms with alkyl halides adsorbed on Pt(111), H/Pt(111), and C/Pt(111) surfaces: Hot-atom and Eley–Rideal reactions. II. Ethyl iodide (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 3218-3224 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The kinetics of reactions of D atoms with ethyl iodide adsorbed on Pt(111), H covered Pt(111), and monolayer C covered Pt(111) surfaces were studied using direct product detection. Ethane, C2H5D, was observed as gaseous product formed through ethyl abstraction from the halide. On C/Pt(111) substrates the reaction kinetics are compatible with the operation of Eley–Rideal mechanisms. At annealed halide submonolayers on C/Pt(111) ethane forms in one step; at three-dimensional halide islands a two-step reaction was observed, probably with a C2H5 radical as intermediate. The measured kinetics could be very well reproduced by a sequence of two Eley–Rideal reaction steps with cross-sections in line with expectations. On Pt(111) and H/Pt(111) substrates the abstraction kinetics of ethyl from the adsorbed halide is controlled by hot-atom mechanisms. Coadsorbed H leads to simultaneous abstraction of H from the surface towards HD and H2, as well as to a gaseous C2H6 product. The ethyl abstraction cross-sections are in the range 0.5 to 1 Å2, in line with direct processes. The results provide further evidence that the substrate, nonmetallic or metallic, is instrumental in controlling the operating Eley–Rideal or hot-atom mechanisms of atom–adsorbate reactions. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479601
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  • 4
    Electronic Resource
    Electronic Resource
    The role of sticking and reaction probabilities in hot-atom mediated abstraction reactions of D on metal surfaces by gaseous H atoms (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 4071-4077 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recent experiments on the abstraction of D adsorbed on metal surfaces with gaseous hydrogen atoms revealed a kinetics of HD formation which is not compatible with the operation of Eley–Rideal (ER) mechanisms. Furthermore, homonuclear products were observed during abstraction, which are not expected through an ER reaction scheme. It was therefore suggested that hot-atom (HA) mechanisms are more appropriate to explain the measured kinetics and products. Random walk calculations of the abstraction kinetics are presented based on a model which exclusively relies on elementary reaction steps which are HA mediated processes. Within this model, the ratio of two variables, the probabilities for hot-atom sticking at empty sites ps and hot-atom reaction with adsorbed species pr, was found to control the kinetics of HD and D2 formation. The essential features of measured kinetic data at Ni(100), Pt(111), and Cu(111) surfaces were reproduced by simple and reasonable assumptions on ps/pr. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477007
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  • 5
    Electronic Resource
    Electronic Resource
    Interaction of gaseous D atoms with CH3I adsorbed on Pt(111), H/Pt(111), and C/Pt(111) surfaces: From hot-atom to Eley–Rideal phenomenology (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 294-300 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The interaction of gaseous D atoms with methyl iodide molecules adsorbed on Pt(111), hydrogen saturated Pt(111), and graphite monolayer covered Pt(111) surfaces was studied. Direct product rate measurements were employed to determine the reaction kinetics. On all substrates, incoming D atoms abstract the methyl group from adsorbed CH3I via gaseous CH3D formation. In the monolayer regime of CH3I/Pt(111) pure hot-atom phenomenology was observed in the rates. With multilayers as targets, the fluence dependence of the rates get Eley–Rideal-type. With a coadsorbed H monolayer present, the CH3D rates at a CH3I monolayer on Pt(111) are affected by the suppression of hot-atom sticking. Accordingly, the rate curves exhibit similar features as expected for Eley–Rideal phenomenology. However, CH4 as a product and simultaneous abstraction of adsorbed H via gaseous HD and H2 formation clearly demonstrate that hot-atom reactions occur. With CH3I adsorbed on a graphite monolayer on Pt(111), the abstraction kinetics of methyl was found to agree with the operation of an Eley–Rideal mechanism. This observation is in line with the expectation that hot atoms do not exist on a C/Pt(111) surface. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476508
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  • 6
    Electronic Resource
    Electronic Resource
    Abstraction of D adsorbed on Pt(111) surfaces with gaseous H atoms (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 3353-3359 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The impact of gaseous H atoms at D covered Pt(111) surfaces at 85 K leads to the formation of gaseous HD and D2 products. The kinetics of formation of these products was measured simultaneously with H exposure for different initial D coverages. The HD and D2 rates as a function of H fluence from the reaction start exhibit common characteristics; a rate step, a rate maximum, and a subsequent exponential rate decay. The HD and D2 rate steps were observed not to scale linear with the D coverage and to increase if on D covered surfaces H was coadsorbed prior to reaction. Of the observed phenomena, only the exponential decay of the HD rate is in line with expectations if an Eley–Rideal mechanism acts in the present reaction. D2 formation, the HD rate step as a function of D coverage, and the presence of a H coadsorbate contradict the Eley–Rideal picture. The results suggest that the reactions towards HD and D2 proceed via hot atom type mechanisms. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475734
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  • 7
    Electronic Resource
    Electronic Resource
    Discrete families of recursive functions and index sets (1994)
    Springer
    Algebra and logic 33 (1994), S. 85-94 
    Details
    ISSN: 1573-8302
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A number of discrete families of recursive functions are studied; exact upper bounds of index sets appearing in the construction are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00739994
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  • 8
    Electronic Resource
    Electronic Resource
    Desert ants on a thermal tightrope (1992)
    [s.l.] : Nature Publishing Group
    Nature 357 (1992), S. 586-587 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] On a summer day in the central Sahara, the silver ant, C. bombycina, is the only arthropod that forages in the full midday sun, even when surface temperatures exceed 60 °C (refs 1, 2). As a scavenger, it searches for other arthropods that were active during the night and early morning but ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/357586a0
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  • 9
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    Noisy CO oxidation on Iridium(111) surfaces (2014)
    Springer
    Details
    Publication Date: 2014-01-01
    Print ISSN: 1951-6355
    Electronic ISSN: 1951-6401
    Topics: Physics
    Published by Springer
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  • 10
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    Experimental Bit Commitment Based on Quantum Communication and Special Relativity (2013)
    American Physical Society
    Details
    Publication Date: 2013-11-01
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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