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  • 1
    Electronic Resource
    Electronic Resource
    Tert-butyl nitrite surface photochemistry: The transition from submonolayer to multilayer behavior (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1688-1701 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photochemistry of tert-butyl nitrite, (CH3)3CONO, adsorbed on Ag(111) at 355 nm has been studied using time-of-flight and reflection adsorption infrared spectroscopy (RAIRS) for coverages ranging from 0.1 to 50 ML. For all coverages a thermal and hyperthermal NO desorption distribution is observed due to photodissociation. The thermal component originates from hyperthermal NO molecules from the first and second layer, which were trapped by the silver substrate. The cross section for photodissociation is independent of coverage and matches the gas phase value. This is consistent with a direct excitation into the S1 state. For coverages exceeding 5 ML the outermost layers still dissociate, but RAIRS shows that in the more inward layers caging is preventing dissociation. Due to caging only isomerization of tert-butyl nitrite is allowed, as is evident from the RAIRS. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475540
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  • 2
    Electronic Resource
    Electronic Resource
    O2 transient trapping-desorption at the Ag(111) surface (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 2477-2491 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular beam scattering experiments of O2 from Ag(111) carried out at a surface temperature of 150 K, which is below the desorption temperature for the molecular chemisorption state, show three different scattering paths: physisorption followed by desorption, direct-inelastic scattering and transient trapping-desorption. The transient trapping-desorption process is attributed to transient adsorption of the molecule in a metastable O2δ− state at the surface. The translational desorption energy of the transiently trapped molecules is far above thermal, strongly dependent on the surface temperature and independent of the translational energy and angle of the incident oxygen molecule. A strongly peaked intensity distribution around the surface normal is observed for the desorption. The transient trapping probability shows a sharp increase above a threshold energy and a subsequent decrease with increasing incidence energy. It is accompanied by a strong broadening in the angular direct-inelastically scattered flux distribution. The possible origin of the metastable O2δ− state will be discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473155
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  • 3
    Electronic Resource
    Electronic Resource
    Dissociative scattering of polyatomic ions from a liquid surface: CF3+ on a perfluoropolyether film (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 10736-10750 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dissociative scattering of CF3+ ions from a liquid insulating perfluorinated polyether surface was explored in the incident energy range 100–500 eV. We have measured the angular and energy distributions of the positive and negative fragment ions. The impulsive energy transfer to the liquid molecules and to internal energy of the scattered ions has been determined as a function of incoming energy and total scattering angle. The energy transfer in the ion/surface collision indicated scattering off the –CF3 groups of the liquid molecules. The dissociation of the CF3+ ions was due to a single impulsive collision with these groups. The parent ion was observed as well as CF2+, CF+, and C+ ions. The degree of dissociation depends only on the total scattering angle and the incoming energy, as in gas phase scattering. Remarkably, negatively charged F− fragment ions were also observed. These were formed in a process referred to as collisionally-induced "ion-pair" formation from neutrals leaving the surface. The important parameter which determined the internal energy uptake of the scattered ions in the collision was the translational energy loss ΔE the parent ion suffered. Finally, a comparison has been made between scattering from a liquid perfluorinated polyether surface and a metal Ag(111) surface. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474189
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  • 4
    Electronic Resource
    Electronic Resource
    Dissociative scattering of fluorocarbon ions from a liquid surface at hyperthermal incident energies (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 2588-2596 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dissociative scattering of CF+, CF2+ and CF3+ ions from a perfluoropolyether (PFPE) surface is explored across the hyperthermal incident energy range 50 to 220 eV. A comparative study on internal energy uptake efficacy and on translational energy transfer to the surface in scattering from the PFPE surface is presented. In addition, measurements are performed on C+ scattering in order to examine the energy transfer to the PFPE liquid surface in more detail. The CF3+ ions take up more internal energy as a function of translational energy transfer in the collision than the CF2+ and the CF+ ions. Furthermore, a detailed analysis and discussion is presented on the surface effective mass as a function of incident (fluoro)carbon ion mass. The analysis is based on elastic scattering from a single group. The results are remarkably different from ion/metal surface scattering. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477979
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  • 5
    Electronic Resource
    Electronic Resource
    Fast energy delocalization upon vibrational relaxation of a deuterated zeolite surface hydroxyl (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 2181-2186 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this time-resolved study of vibrational dynamics of deuterated surface hydroxyls at acid sites in the zeolite Mordenite, we investigate the O–D T1 vibrational lifetime and transient band shifts. It is shown that after infrared excitation of the stretching mode of a surface hydroxyl, the excess energy is rapidly distributed over delocalized low-energy lattice modes upon de-excitation. This is asserted from the observation that nonexcited hydroxyls are perturbed by the relaxation of their excited counterparts immediately after this relaxation. This observation can be made owing to better resolution in transient transmission spectroscopy obtained by deuteration of the surface hydroxyls. This assignment allows for accurate estimates of lattice temperatures after relaxation of the vibration. Further, from the observation that the vibrational lifetime is dependent on frequency (increasing from 25 to 70 ps with increasing frequency), it is concluded that the deuterated acidic protons are hydrogen bonded to lattice oxygen atoms in the zeolite. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468740
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  • 6
    Electronic Resource
    Electronic Resource
    Direct inelastic scattering of oriented NO from Ag(111) and Pt(111) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 5197-5207 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A pulsed supersonic and cold oriented beam of NO molecules is incident upon the (111) face of clean Ag and Pt single crystal surfaces. The steric effect in the scattered density distributions is determined by a quadrupole mass spectrometer. It is found that the steric effect in the peak in the distribution of direct inelastically scattered molecules depends linearly on the reflection angle. In all circumstances O-end collisions lead to scattering angles more inclined towards the surface than N-end collisions. For the Pt(111) surface a much stronger steric effect is measured than for the Ag(111) surface. The steric effect seems to scale with the incident normal velocity. These strong steric effects can be explained by the larger trapping probability for the N-end orientation and a leverage effect due to the high trapping probability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460556
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  • 7
    Electronic Resource
    Electronic Resource
    Isotope effect in dissociative chemisorption of O2 on Ag(111) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2368-2369 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459908
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  • 8
    Electronic Resource
    Electronic Resource
    Probing the (dual) repulsive wall in the interaction of O2, N2, and Ar with the Ag(111) surface (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 6217-6231 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have performed molecular beam scattering experiments of O2, N2, and Ar from the Ag(111) surface in the translational energy regime from 0.2 to 2.6 eV and at surface temperatures of 600 and 150 K. The experiments were carried out to probe the repulsive part in the particle–surface interaction potential. It is shown that the scattering dynamics of the systems N2–Ag(111) and Ar–Ag(111) is characteristic of physisorption systems. The scattering data for the system O2–Ag(111) shows that both the physisorption and chemisorption part of the interaction potential are probed in the experiment. For "normal incidence energies'' exceeding a threshold energy, the barrier to the chemisorption part of the interaction potential can be crossed. An upper limit for this threshold is Ei cos2 θi=0.3 eV. Although the chemisorption region is probed, the (dissociative and nondissociative) chemisorption probability remains negligible. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470449
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  • 9
    Electronic Resource
    Electronic Resource
    Rotational excitation of oriented molecules as a probe of molecule-surface interaction (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 8409-8421 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100174a067
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  • 10
    Electronic Resource
    Electronic Resource
    Infrared picosecond transient hole-burning studies of the effect of hydrogen bonds on the vibrational line shape (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 3431-3442 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: With infrared transient hole-burning spectroscopy we have investigated the influence of OD⋅⋅⋅X hydrogen bonds on the vibrational line shape of O–D stretch vibrations in acid zeolites. The effect of hydrogen bonding on the line shape depends critically on the type of hydrogen bond. For hydrogen bonding in a rigid structure, the hydrogen bond determines the inhomogeneous linewidth, but the homogeneous linewidth is determined by coupling to a ∼200 cm−1 lattice mode as concluded from the temperature dependence of the dephasing rate. When the hydrogen bond is formed with an adsorbing molecule, the coupling between the high-frequency O–D stretch vibration and the low-frequency OD⋅⋅⋅X hydrogen-bond stretching mode does determine the homogeneous linewidth. The difference between the two systems can be explained by the different hydrogen-bond potentials. Variation of the adsorbate provides a means of obtaining conclusive information on the coupling mechanism between the high-frequency O–D stretching mode and the low-frequency OD⋅⋅⋅X hydrogen-bond stretching mode. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472213
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