| 1. |
- Andersson, T., et al.
(författare)
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Selective adsorption, bound states, and potential parameters for He, Ne, and Ar interacting with a Cu(110) surface
- 2006
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Ingår i: J. Chem. Phys.. - : AIP Publishing. - 0021-9606. ; 124
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Tidskriftsartikel (refereegranskat)abstract
- Using nozzle beams of He, Ne, and Ar, we have measured diffractive selective adsorption resonances from a Cu(110) surface kept at 20 K. Bound state energies of the atom-surface potentials have been determined from plots of the measured resonance energies versus incident angle and their fits to calculated kinematical dispersion relations. For 3He and 4He we have found a unique level assignment that is compatible with a single gas-surface potential curve with a well depth of 6.05 meV of the He–Cu(110) potential. This value is about 10% larger than the prediction of 5.55 meV from the current physisorption theory. The Ne and Ar data reveal a large number of closely spaced levels with level separations and estimated van der Waals coefficients that are compatible with available theoretical data.
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| 2. |
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| 3. |
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| 4. |
- Gustafsson, Kristian, 1972, et al.
(författare)
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Infrared spectroscopy of physisorbed and chemisorbed N-2 in the Pt(111)(3x3)N-2 structure
- 2007
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127:19
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Tidskriftsartikel (refereegranskat)abstract
- Using infrared spectroscopy and low electron energy diffraction, we have investigated the adsorption of N-2, at 30 K, on the Pt(111) and the Pt(111)(1x1)H surfaces. At monolayer coverage, N-2 orders in commensurate (3x3) structures on both surfaces, and we propose that the unit cells contain four molecules in each case. The infrared spectra reveal that N-2 exclusively physisorbs on the Pt(111)(1x1)H surface, while both physisorbed and chemisorbed N-2 is detected on the Pt(111) surface. Physisorbed N-2 is the majority species in the latter case, and the two adsorption states show an almost identical uptake behavior, which indicates that they are intrinsic constituents of the growing (3x3) N-2 islands. An analysis of the infrared absorbance data, based on a simple scaling concept suggested by density functional theory calculations, supports a model in which the (3x3) unit cell contains one chemisorbed molecule in end-on atop configuration and three physisorbed molecules. We note that a classic ''pinwheel'' structure on a hexagonal lattice, with the end-on chemisorbed N2 molecules acting as ''pins,'' is compatible with this composition. (C) 2007 American Institute of Physics.
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| 5. |
- Linde, Petter, 1972, et al.
(författare)
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High resolution resonance measurements of the physisorption interaction
- 2006
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Ingår i: Phys. Rev. Lett.. - 0031-9007. ; 96
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Tidskriftsartikel (refereegranskat)abstract
- Narrow selective adsorption resonances, with line widths given by the natural lifetime of the intermediate resonance state, have been observed directly in the angular distributions of Ne nozzle beams diffracted from a 20 K Cu(110) surface. Using beams of 20Ne and 22Ne isotopes we show that this high-resolution mode of resonance detection permits, even in a case of a small isotope effect, unique assignment of bound level sequences compatible with a single gas-surface potential curve.
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| 6. |
- Svensson, Krister, 1969, et al.
(författare)
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Dipole active rotations of physisorbed H2 and D
- 2005
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Ingår i: Physics Reveiw B. - 0163-1829 .- 2469-9969 .- 2469-9950. ; 71
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Tidskriftsartikel (refereegranskat)abstract
- We have, in electron-energy-loss measurements, observed dipole activity associated with the j=02 rotational transitions for H2 and D2 physisorbed on a Cu(100) surface and at Au adatoms on this surface. Such dipole transitions, which are forbidden for the free molecules, provide for example, via rotation-translation conversion, channels for infrared photodesorption. Using two simple dipole moment functions, we have, for the bare Cu(100) surface, calculated dipole matrix elements for the rotational transition and its combination mode with the =01 vibrational transition in the physisorption well. Our calculations reveal that the anisotropy of the molecular electronic polarizability induces a significant dynamic dipole coupled to the rotational and rotational-vibrational motion, but are unable to reproduce the measured relative intensities of the corresponding transitions.
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| 7. |
- Svensson, Krister, 1969-, et al.
(författare)
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Fast ortho-para conversion of H2 adsorbed at copper surface step atoms
- 2007
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Ingår i: Phys. Rev. Lett.. - : American Physical Society. - 0031-9007. ; 98:9
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Tidskriftsartikel (refereegranskat)abstract
- Ortho-para conversion of H2 adsorbed at the step atoms of a Cu(510) surface proceeds with a short conversion time constant around 1 s as observed in electron-energy-loss measurements of rotational populations. We suggest that this rapid conversion is related to the special character of the adsorption state, which involves a short H2-Cu bond length of 1.8 Å. On the flat Cu(100) surface, conversion is found to occur at active sites, most likely step atoms
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