| 1. |
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| 2. |
- Andersen, J. N., et al.
(author)
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Alkali metal adsorption on Al(111)
- 1993
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In: Surface Science. - : Elsevier BV. - 0039-6028. ; 289:3, s. 307-334
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Journal article (peer-reviewed)abstract
- The submonolayer adsorption of Na, K, Rb, and Cs on the Al(111) surface at 100 K and at room temperature is investigated by high resolution core level spectroscopy and low energy electron diffraction. It is found that the first alkali atoms on the surface adsorb at surface defects. At higher coverages, up to approximately one third of the maximum submonolayer coverage, alkali atoms adsorbed at defects coexist with a dispersed phase. At higher coverages island formation is found to occur for the majority of the systems. It is argued that all of the ordered structures formed at room temperature involve a disruption of the Al(111) surface in contrast to the situation at 100 K where the alkali atoms adsorb as adatoms.
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| 3. |
- Andersen, J. N., et al.
(author)
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Changes in the local surface geometry with conserved adsorbate coverage and long-range order caused by annealing
- 1992
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In: Physical Review B (Condensed Matter). - 0163-1829. ; 46:19, s. 12784-12787
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Journal article (peer-reviewed)abstract
- The ordered c(2×2) Na on Al(100) and (3 × 3) R30°K on Al(111) structures formed at either 100 K or at room temperature are studied by high-resolution core-level spectroscopy. For both systems equal alkali coverages are found at these two temperatures. The core-level spectra, however, show strong changes with temperature. This behavior leads to the surprising conclusion that annealing at room temperature causes an irreversible change in the local geometry, i.e., of the adsorption site, of the overlayer even though neither the long-range order nor the adsorbate coverage changes.
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| 4. |
- Andersen, J. N., et al.
(author)
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Differences in the Cs 4d and 5p surface and interface core-level shifts
- 1994
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In: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 226:1-2, s. 106-110
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Journal article (peer-reviewed)abstract
- Core-level binding energy shifts of Cs induced by changes in the surroundings of the Cs atoms are measured for two different Cs core levels, 5p and 4d, and are found to be different for these two levels. The surface core-level shift of Cs is found to differ by 25 meV between the two levels. In the case of the Cs core-level shifts between bulk Cs atoms and Cs atoms at an interface between Cs and an Al(111) surface the difference between the two levels is found to be as large as 60 meV. The implications of these results for the precision of the Z+1 approximation are discussed.
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| 5. |
- Andersen, J. N., et al.
(author)
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Intermixing in the Na on Al(111) system
- 1992
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In: Physical Review Letters. - 0031-9007. ; 68:1, s. 94-97
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Journal article (peer-reviewed)abstract
- Ordered structures formed by Na adsorption on the Al(111) surface are investigated by high-resolution core-level spectroscopy. It is shown that, contrary to the common picture of alkali adsorption, two of the structures formed at room temperature consist of intermixed Na-Al layers. The results for the (3 ×)-rotated-30°structure are also consistent with intermixing although they do not provide any definite proof. For Na layers deposited at 100 K no intermixing is found.
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| 6. |
- Andersen, J. N., et al.
(author)
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Surface core-level shifts of some 4d-metal single-crystal surfaces : Experiments and ab initio calculations
- 1994
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In: Physical Review B (Condensed Matter). - 0163-1829. ; 50:23, s. 17525-17533
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Journal article (peer-reviewed)abstract
- High resolution measurements are reported of the surface core-level shift of the 3d level for the Rh(111), Rh(110), Pd(111), Pd(110), and Ag(111) single-crystal surfaces. These measurements and earlier ones for the Mo(110), Rh(100), and Pd(100) surfaces are analyzed by ab initio calculations of the surface core-level shift. The calculations are found to reproduce well the trends of the experimental shifts with the 4d metal and with the crystal plane. The comparison between these experimental and theoretical results demonstrates the importance of proper inclusion of final-state effects for accurate calculations of surface core-level shifts. A core hole in a surface atom is found to be better screened than one in a bulk atom for the 4d metals to the left of Pd in the Periodic Table. The use of the Z+1 approximation to describe the core hole is investigated both by explicit use of this approximation and by performing calculations for 1s and 3d core holes, respectively. The Z+1 approximation is found to be well obeyed in the case of Ag whereas for the rest of the 4d transition metals it is less precise, introducing errors of typically 0.1 eV.
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| 7. |
- Berg, C., et al.
(author)
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Observation of a low-binding-energy peak in the 2p core-level photoemission from oxidized Al(111)
- 1993
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In: Physical Review B (Condensed Matter). - 0163-1829. ; 47:19, s. 13063-13066
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Journal article (peer-reviewed)abstract
- High-resolution photoemission studies of oxidation of the Al(111) surface have been performed. The appearance of a component at lower binding energy than the metallic bulk Al emission in the Al 2p spectrum at oxygen exposures above ∼50 langmuir (1 L = 10-6 Torr s) is argued to be due to Al atoms which do not bond directly to oxygen atoms at the oxide-metal interface. Low-energy electron diffraction initially shows a 1×1 structure, which subsequently fades away at higher oxygen exposures, 400 L.
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| 8. |
- Bäckman, B, et al.
(author)
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The absence of correlations between a clinical classification and ultrastructural findings in amelogenesis imperfecta.
- 1993
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In: Acta odontologica Scandinavica. - 0001-6357. ; 51:2, s. 79-89
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Journal article (peer-reviewed)abstract
- This study was performed to examine whether a clinical classification of different phenotypes of amelogenesis imperfecta could be discernible at the ultrastructural level. Seventeen primary teeth from 16 children with hypomineralization, hypomaturation, or hypoplastic variants of the disease were collected for histologic studies of the enamel by means of polarized light microscopy, scanning electron microscopy (SEM), and secondary ion mass spectrometry (SIMS). Polarization microscopy showed that the enamel was hypomineralized; in six teeth a wavy configuration of the enamel prisms also appeared. Three histomorphologic main types could be discerned. In 10 of the teeth extensive hypomineralization of the bulk of the enamel was found. One tooth had an unusually thick enamel with only a thin normally mineralized surface layer. SIMS images showed less pronounced signals from Ca2+ and Na+ but with stronger signals from Cl- and CN-, representing the organic component of enamel. The SEM images showed an irregular prism pattern with marked interprismatic areas. Irrespective of the clinical appearance or the hereditary pattern the main findings were hypomineralized enamel with or without wavy bands. Neither of the analytical methods used in this paper distinguishes between the clinical phenotypes of amelogenesis imperfecta.
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| 9. |
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| 10. |
- Heskett, D., et al.
(author)
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Alkali-alkali interactions on Al(111) : segregation and islanding in Na-Rb mixtures
- 1994
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In: Surface Science. - 0039-6028. ; 316:3, s. 303-308
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Journal article (peer-reviewed)abstract
- The low temperature coadsorption of Na and Rb on an Al(111) surface is examined with a combination of LEED and core level photoemission spectroscopy. We observe LEED pattern sequences and alkali core level binding energies which are consistent with a net total alkali coverage and can be explained by Na-Rb repulsion, segregation, and islanding, though other models cannot be definitely excluded.
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