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  • 1
    ISSN: 1573-7357
    Keywords: 71.27. + a ; 74.72.Jt ; 79.60. −i ; 79.20.Kz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Sr2CuO2Cl2. represents a nearly ideal case of a 2-D antiferromagnetic CuO2-plane and thus is of particular interest in the context of the origins of high TC superconductivity. We present high energy spectroscopic results on single crystalline Sr2CuO2Cl2. Using electron-energy loss spectroscopy in transmission we have measured the loss function along the high symmetry directions in the CuO2-plane. X-ray photoemission spectroscopy is applied to study the valence band and the Cu 2p spectrum. Comparison of the experiment to a cluster calculation is given.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic structure of the prototypical corner-sharing Sr2CuO3 linear chain compound is investigated by combining several theoretical and experimental techniques. Band structure calculations within the local density approximation and using a local orbital basis provided the relevant orbitals and the transfer integrals for a four-band extended Hubbard pd-model, which was treated by means of exact diagonalization and of quantum Monte Carlo calculations for finite chain clusters. The band structure values of the transfer integrals t pd exceed the corresponding values for layered cuprates. Enhanced values of the intersite Coulomb interaction, V pd = 2 ... 2.5 eV, and a difference between the onsite energies of side and chain oxygen Δpp = 0.5 ... 0.75 eV are deduced from the comparison of the model studies with the intensities of polarization dependent x-ray absorption spectra. The latter reflect the hole distribution over the oxygen sites.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1987), S. 321-329 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The increasing importance of spectroscopic methods as an analytical tool in industry, combined with the trend to automatize spectrometers, demands new standards in the quantity and quality of spectrum interpretation. Suitable computer programs should be able to predict structural features from mass spectral properties. The knowledge base is a structure-oriented mass spectral data collection consisting of some 42000 spectra and topologies. The comparison of selected mass spectral properties such as similarity, neutral losses and ion series of the unknown with the equivalent properties of the library spectra results in a set of corresponding structures. Subsequent substructure analysis yields a histogram of substructure frequencies containing information about their statistical relevance. The relevant substructure set may be recombined to produce a structure proposal, as is demonstrated for 1-acetyl-2-methoxy-4-trimethylsilyioxybenzene. In a second example, the relevant substructures derived by the interpretation system are used as input for the 13C-NMR substructure generator. This procedure reduces the solution space of the structure prediction algorithm considerably. Besides the spectrum interpretation, additional possibilities are available. The substructure search enables us, for example, to look for mass spectrometric reaction centres. Beyond that, substructure analysis is applicable to the determination of structural features typical of certain combinations of neutral losses and/or characteristic fragments.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 24 (1986), S. 1089-1092 
    ISSN: 0749-1581
    Keywords: On-line NMR ; NMR spectrometer/chemical reactor coupling ; Time dependent concentration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The basis of the evaluation of chemical processes is a comprehensive knowledge about the concentration profiles of the reactants as a function of time. Normally, analytical samples are taken from the reaction medium, with the disadvantage that the analysis does not occur on the reaction time scale and the reaction equilibrium itself is disturbed. For this reason, an on-line analytical system based on the coupling between an NMR spectrometer and a chemical reactor was developed.The applicability of the system is demonstrated on a Wittig reaction, the last step in the synthesis of retinoic acid. 31P NMR was employed for the detection of the time dependent concentration of phosphorylated reaction components. The consequences of the results with respect to a change of the chemical process are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2015-02-10
    Description: Picosecond magnetization dynamics in the free and pinned layers of a microscale magnetic tunnel valve have been studied using time-resolved scanning Kerr microscopy. A comparison of the observed dynamics with those of individual free and pinned layers allowed the effect of interlayer coupling to be identified. A weak interlayer coupling in the tunnel valve continuous film reference sample was detected in bulk magnetometry measurements, while focused Kerr magnetometry showed that the coupling was well maintained in the patterned structure. In the tunnel valve, the free layer precession was observed to have reduced amplitude and an enhanced relaxation. During magnetization reversal in the pinned layer, its frequency approached that of the low frequency mode associated with the free layer. At the pinned layer switching field, the linewidth of the free layer became similar to that of the pinned layer. The similarity in their frequencies promotes the formation of precessional modes that exhibit strong collective properties such as frequency shifting and enhanced linewidth, while inhomogeneous magnetization of the pinned layer during reversal may also play a role in these observations. The collective character of precessional dynamics associated with mixing of the free and pinned layer magnetization dynamics must be accounted for even in tunnel valves with a small interlayer coupling.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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