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Träfflista för sökning "WFRF:(Schnadt J.) srt2:(2000-2004)"

Sökning: WFRF:(Schnadt J.) > (2000-2004)

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  • Schnadt, J, et al. (författare)
  • Excited-state charge transfer dynamics in systems of aromatic adsorbates on TiO2 studied with resonant core techniques
  • 2003
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 119:23, s. 12462-12472
  • Tidskriftsartikel (refereegranskat)abstract
    • Resonant core spectroscopies are applied to a study of the excited electron transfer dynamics on a low-femtosecond time scale in systems of aromatic molecules (isonicotinic acid and bi-isonicotinic acid) adsorbed on a rutile TiO2(110) semiconductor surface. Depending on which adsorbate state is excited, the electron is either localized on the adsorbate in an excitonic effect, or delocalizes rapidly into the substrate in less than 5 fs (3 fs) for isonicotinic acid (bi-isonicotinic acid). The results are obtained by the application of a variant of resonant photoemission spectroscopy. (C) 2003 American Institute of Physics.
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  • Schnadt, Joachim, et al. (författare)
  • Structural study of adsorption of isonicotinic acid and related molecules on rutile TiO2(110) I: XAS and STM
  • 2003
  • Ingår i: Surface Science. - 0039-6028. ; 540:1, s. 39-54
  • Tidskriftsartikel (refereegranskat)abstract
    • X-ray absorption spectroscopy (XAS) and scanning tunneling microscopy (STM) have been used to study the absorption of monolayers of the pyridinecarboxylic acid monomers (isonicotinic acid, nicotinic acid, and picolinic acid) and benzoic acid on a rutile TiO2(1 1 0) surface. We find that the pyridine and phenyl rings are oriented with their planes largely perpendicular to the surface. The azimuthal orientations are strongly influenced by adsorbate-adsorbate interactions, which in each case leads to at least two different molecular species. In order to reach this conclusion a detailed strategy has been developed for the interpretation of angle-dependent XAS data, which does not rely on any curve fitting procedures. (C) 2003 Elsevier B.V. All rights reserved.
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  • O'Shea, J. N., et al. (författare)
  • Hydrogen-bond induced surface core-level shift in isonicotinic acid
  • 2001
  • Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 105:10, s. 1917-1920
  • Tidskriftsartikel (refereegranskat)abstract
    • Intermolecular hydrogen-bonding in thick films of isonicotinic acid evaporated onto rutile TiO2(110) has been investigated with X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The rate of deposition is found to be a key factor in overcoming the kinetic barriers to extensive hydrogen-bond formation, which, when present, gives rise to large energy shifts between bulk and surface in both the N1s XPS and XAS. The origin of the surface core-level shift is attributed to the presence of non-hydrogen-bonded nitrogen atoms in the surface layer.
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  • O'Shea, J. N., et al. (författare)
  • Hydrogen-bond induced surface core-level shift in pyridine carboxylic acids
  • 2001
  • Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 486:3, s. 157-166
  • Tidskriftsartikel (refereegranskat)abstract
    • Intermolecular hydrogen bonding in thick films of pyridine carboxylic acids (isonicotinic; picolinic and bi-isonicotinic acid) evaporated onto rutile TiO2(1 1 0) has been investigated with X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. These molecules are shown to be strongly H-bonded in the condensed phase, and a surface core-level shift is observed due to the presence of non-H-bonded nitrogen atoms in the surface layer. Density functional theory calculations are used to relate the experimental data to the proposed bonding configurations based on the surface termination of the known equilibrium solid-state structure. A kinetic barrier, attributed to the high degree of molecular orientation required for the formation of extended H-bonding networks, has also been investigated.
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  • Schiessling, J, et al. (författare)
  • Insulating surface layer on single crystal K3C60
  • 2004
  • Ingår i: European Physical Journal B. Condensed Matter and Complex Systems. - : Springer Science and Business Media LLC. - 1434-6028. ; 41:4, s. 435-438
  • Tidskriftsartikel (refereegranskat)abstract
    • Using angle-dependent photoemission spectra of core and valence levels we show that metallic, single crystal K3C60 is terminated by an insulating or weakly-conducting surface layer. We attribute this to the effects of strong intermolecular correlations combined with the average surface charge state. Several controversies on the electronic structure are thereby resolved.
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  • Schnadt, J, et al. (författare)
  • Structural study of adsorption of isonicotinic acid and related molecules on rutile TiO2(110) II: XPS
  • 2003
  • Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 544:1, s. 74-86
  • Tidskriftsartikel (refereegranskat)abstract
    • The adsorption of monolayers of the pyridine-carboxylic acid monomers (isonicotinic acid, nicotinic acid, and picolinic acid) on rutile TiO2(1 1 0) has been studied by means of X-ray photoemission spectroscopy. An investigation of the O 1s spectra shows that the molecular carboxylic groups are deprotonated and, hence, that the molecules bind to the surface in a bidentate mode. Moreover, the binding energy of those core levels that are related to the pyridine ring atoms shift as a function of molecule relative to the substrate O 1s and Ti 3p levels, while the position of the core levels related to emission from the carboxylic group are constant relative to the substrate levels. The molecule-dependent shifts are attributed to local intermolecular interactions that determine the proximity of adjacent molecular rings and thus the core-hole screening response of the neighbouring molecules. We propose a simple molecular arrangement for each case which satisfies the known constraints. (C) 2003 Elsevier B.V. All rights reserved.
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  • O'Shea, JN, et al. (författare)
  • Hydrogen-bond induced surface core-level shift in isonicotinic acid
  • 2001
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Intermolecular hydrogen-bonding in thick films of isonicotinic acid evaporated onto rutile TiO2(110) has been investigated with X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The rate of deposition is found to be a key fac
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  • O'Shea, JN, et al. (författare)
  • Hydrogen-bond induced surface core-level shift in pyridine carboxylic acids
  • 2001
  • Ingår i: SURFACE SCIENCE. - : ELSEVIER SCIENCE BV. - 0039-6028. ; 486:3, s. 157-166 Language: English
  • Tidskriftsartikel (refereegranskat)abstract
    • Intermolecular hydrogen bonding in thick films of pyridine carboxylic acids (isonicotinic; picolinic and bi-isonicotinic acid) evaporated onto rutile TiO2(1 1 0) has been investigated with X-ray photoelectron spectroscopy and X-ray absorption spectroscopy
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16.
  • Persson, Petter, et al. (författare)
  • N1s x-ray Absorption Study of the Bonding Interaction of Bi-Isonicotinic Acid on Rutile TiO2 (110)
  • 2000
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 112:9, s. 3945-3948
  • Tidskriftsartikel (refereegranskat)abstract
    • N1s x-ray absorption spectra of bi-isonicotinic acid (2,28-bipyridine–4,48-dicarboxylic acid! on rutile TiO2(110) have been studied experimentally and quantum chemically. Differences between multilayer and monolayer spectra are explained by the adsorbate bonding to the substrate. A connection to the electronic coupling in dye-sensitized electrochemical devices is made.
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  • Schnadt, J, et al. (författare)
  • Alignment of valence photoemission, x-ray absorption, and substrate density of states for an adsorbate on a semiconductor surface
  • 2003
  • Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 67:23
  • Tidskriftsartikel (refereegranskat)abstract
    • A method for determining the placement of x-ray absorption data into an experimental density of states for an adsorbate-semiconductor system is motivated and illustrated with the cases of bi-isonicotinic acid, isonicotinic acid, and benzoic acid on rutile TiO2(110). Special attention is paid to experimental aspects, as well as the role of Z+1 effects and the choice of reference level.
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  • O'Shea, JN, et al. (författare)
  • X-ray photoelectron spectroscopy of low surface concentration mass-selected Ag clusters
  • 2000
  • Ingår i: JOURNAL OF CHEMICAL PHYSICS. - : AMER INST PHYSICS. - 0021-9606. ; 113:20, s. 9233-9238
  • Tidskriftsartikel (refereegranskat)abstract
    • We have developed an experimental setup for the study of small mass-selected clusters delivered by soft landing to a model oxide support. An automated deposition system to achieve accurately quantified homogeneous surfaces is described which also overcome
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  • Schnadt, J, et al. (författare)
  • Adsorption and charge-transfer study of bi-isonicotinic acid on in situ-grown anatase TiO2 nanoparticles
  • 2004
  • Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 108:10, s. 3114-3122
  • Tidskriftsartikel (refereegranskat)abstract
    • Bi-isonicotinic acid (2,2'-bipyridine-4,4'-dicarboxylic acid) is an important ligand in the chemistry of organometallic devices. Here, the adsorption of a monolayer of the molecule on in situ-grown anatase TiO2 nanoparticles has been investigated by means of X-ray photoemission spectroscopy and X-ray absorption spectroscopy. The bonding geometry is determined to be 2M-bidentate. Furthermore, resonant core spectroscopies have been used to study the excited-state-dependent electron transfer from the core-excited molecule to the substrate. For an excitation to the lowest unoccupied orbital, the excited electron is localized on the molecule because of a core-excitonic effect. Excitation to the two following unoccupied orbitals leads to a charge transfer on a low-femtosecond time scale. This study shows that there is no essential difference in charge-transfer characteristics, compared to the case of adsorption on the rutile (110) surface, for states degenerate with the conduction band.
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  • Schnadt, J, et al. (författare)
  • Electron-spectroscopy study of LiC60: Charge transfer and dimer formation
  • 2000
  • Ingår i: PHYSICAL REVIEW B. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 62:7, s. 4253-4256
  • Tidskriftsartikel (refereegranskat)abstract
    • Li-C-60 compounds LixC60 were studied for average Li concentration (x) over bar less than or equal to 1 using photoelectron spectroscopy. Strong evidence is found for the formation of LiC60 dimers, as well as a second phase. The study suggests that the sm
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