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  • 1
    Electronic Resource
    Electronic Resource
    Piezo-XAFS–time-resolved x-ray absorption spectroscopy : Papers from the 12th National Synchrotron Radiation Instrumentation Conference (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1668-1670 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The piezo-x-ray absorption spectroscopy technique is a novel tool for time-resolved x-ray absorption spectroscopy in the hard x-ray range. It makes use of piezo tilt tables mounted below the crystals in a double crystal or channel cut crystal monochromator. Repetitive energy scans are performed by applying an oscillatory high voltage to the piezo translators of the tilt tables. Currently, this allows one to scan an energy range of several hundred eV in the hard x-ray range with repetition frequencies of typically 10 Hz. The capability to record full extended x-ray absorption fine structure spectra on a subsecond time scale is demonstrated. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1445832
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A novel crystal bender for x-ray synchrotron radiation monochromators : Papers from the 12th National Synchrotron Radiation Instrumentation Conference (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1564-1567 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new bending mechanism for an indirectly water cooled monochromator crystal has been developed. The main design goals were a lightweight construction, ease of manufacture, and control. The construction consists of a U-shaped first Si(111) crystal, which can be bent by compressed air to compensate the bowing induced by the heat load from the impinging white synchrotron radiation. The performance of the system was tested at the x-ray undulator beamline BW1 at HASYLAB (Hamburg, Germany). For heat loads between ∼100 and 400 W, rebending of the crystal significantly increases the intensity of the monochromatic beam while the rocking curve is narrowed accordingly, typical widths obtained at 8.9 keV photon energy amount to about 10 arc sec. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1445817
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  • 3
    Electronic Resource
    Electronic Resource
    XAFS investigations of tin nitrides (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 698-700 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Tin nitrides (Sn3N4) prepared by the reaction of Sn-halides with KNH2 in liquid ammonia and a subsequent vacuum annealing procedure were investigated with transmission mode XAFS experiments. While the near edge data suggest the presence of a univalent Sn-compound with a valency close to +4, the analysis of the extended X-ray absorption fine structure proves the presence of two different local Sn sites in this crystal structure: While Sn(1) is surrounded by 4 nitrogen in a distance of 2.06 Å, each Sn(2) ion is coordinated with 6 nitrogen at about 2.17 Å radial distance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049500015119
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  • 4
    Electronic Resource
    Electronic Resource
    Piezo-QEXAFS with fluorescence detection: fast time-resolved investigations of dilute specimens (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 6-9 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: First X-ray absorption spectroscopy experiments with a vibrating piezo-driven double-crystal monochromator (piezo-QEXAFS) and fluorescence detection are reported. It is shown that high-quality XANES spectra can be recorded on a time scale of about 50 ms per spectrum, even for very low concentrations of 〈10 mmol l−1 using fluorescence detection. The quality of the spectra, possible applications, as well as present limits of the technique will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049500018033
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  • 5
    Electronic Resource
    Electronic Resource
    Piezo-QEXAFS: advances in time-resolved X-ray absorption spectroscopy (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 354-356 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The Piezo-QEXAFS technique is a novel tool for time-resolved X-ray absorption spectroscopy in the hard X-ray range. Monochromator components consisting of specialized tilt stages to perform fast energy scans, lightweight crystal holders, bending mechanics, and control electronics are being installed and commissioned. It is planned to perform fast EXAFS scans with time resolution in the millisecond range. With Piezo-QEXAFS all typical X-ray absorption experiments will be possible as it retains the standard linear geometry. The achieved time resolution opens interesting insights into the dynamics of phase transitions and chemical reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049500017064
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  • 6
    Electronic Resource
    Electronic Resource
    Reflection mode XAFS investigations of reactively sputtered thin films (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 478-480 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Amorphous Ta-oxide and Sn-nitride thin films were prepared by reactive sputter deposition on smooth float glass substrates and investigated ex situ using reflection mode XAFS. The absorption coefficient μ and its fine structure were extracted from the measured reflection mode XAFS spectra with a method based on the Kramers-Kronig transform. Bond distances, coordination numbers and Debye-Waller factors were determined by a detailed XAFS data analysis and compared to those of reference compounds. In addition, changes of the atomic short range order of the sputter deposited Ta2O5-films induced by a thermal heat treatment in ambient air were examined as a function of the annealing temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049500019701
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  • 7
    Electronic Resource
    Electronic Resource
    Vinylogous β-Carotenes: Generation, Storage, and Delocalization of Charge in Carotenoids (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2205-2213 
    Details
    ISSN: 0947-3440
    Keywords: Carotenoids ; C26—C70 β-carotenes ; Cyclic voltammetry ; Photoelectron spectroscopy ; Semiempirical calculations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper, we report on the synthesis of β-carotenes of variable chain length with between 5 and 23 double bonds (1-7). These oligoenes were prepared by McMurry and Wittig reactions. The tetradecapreno-β-carotene 7 would seem to be the longest β-carotene yet reported. Furthermore, we investigated the electronic properties using cyclic voltammetry and photoelectron spectroscopy (UPS) to generate open-shell and closed-shell ions of carotenoids in solution and in the solid state, respectively. With increasing chain length (≥ 11 double bonds), even the generation of tetracations and tetraanions could be observed by cyclic voltammetry. Extending the number of conjugated bonds causes the potentials to converge to limiting values. All electron-transfer processes occur in one-electron steps, which are close to each other in pairs. The potential difference between the first oxidation potential and the first reduction potential is a linear function of the reciprocal chain length. Despite the different techniques used (CV and UPS) and the different condensed phases, there is an excellent correspondence between the energies of the radical cation states generated by the two methods. This shows that the radical cation formation is principally determined by the chain length. The structures of the ion states were investigated using semiempirical methods at the NDDO level. Charge delocalization and bond relaxation are not identical and do not utilize the same number or the same kind of atoms. It can be shown that from the length of 20 double bonds onwards, the effective conjugation length for doubly-charged cations converges slowly to a limiting value.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971106
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  • 8
    Book
    Book
    Scientific computing in electrical engineering . proceedings of the 3rd international workshop, August 20-23, 2000, Warnemünde, Germany; 18 (2001)
    Berlin u.a. :Springer,
    Details
    Title: Scientific computing in electrical engineering . proceedings of the 3rd international workshop, August 20-23, 2000, Warnemünde, Germany; 18
    Contributer: VanRienen, Ursula , Günther, Michael , Hecht, Dirk , Rienen, U. van , Günther, M. , Hecht, D.
    Publisher: Berlin u.a. :Springer,
    Year of publication: 2001
    Pages: 424 S.
    Series Statement: Lecture notes in computational science and engineering 18
    Type of Medium: Book
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