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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 18 (1996), S. 231-235 
    ISSN: 0392-6737
    Keywords: Mössbauer spectra ; Structure, bonding, conformation, configuration and isomerism of biomolecules ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Using the possibility to produce61Co sources at the MAinz MIcrotron,61Ni Mössbauer spectroscopy was applied to different kinds of chemical problems. Measurements of isomer shifts andV zz values in some common compounds and compounds with unusual chemical bonding for comparison with band structure calculations, measurement of61Ni Mössbauer parameters in model compounds for hydrogenase and dehydrogenase with an active [NiS4] centre, and study of novel binary NiF3 compounds at helium temperature are presented.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 43 (1987), S. 213-218 
    ISSN: 1432-0630
    Keywords: 75.30 ; 76
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Antimony substituted nickel ferrites Co x Ni5/3−x FeSb1/3O4 withx=0,1/3,1,4/3, and 5/3 were prepared by the common ceramic technique, and the single-phase structure was confirmed by x-ray powder diffraction.57Fe Mössbauer spectra were recorded at 4.2 K with and without an applied magnetic fieldH long=60 kOe in order to determine the cation distribution and the spin structure. Utilizing the cation distributions and the Yafet-Kittel spin structures for B-site Fe3+ ions, derived from Mössbauer experiments the calculated magnetic moments are in excellent agreement with the experimental values at 4.2 K. The existence of Ni2+ ions in crystallographic A-sites was confirmed by61Ni Mössbauer spectroscopy. The magnitude of the supertransferred hyperfine field at121Sb nuclei is determined mainly by a covalent spin charge transfer from A-sites, occupied by Fe3+, Ni2+, and Co2+ ions, into the 5s orbital of Sb5+ ions. The different contributions of various magnetic A-site ions to H STHF Sb may be understood by combining the energy differences between the ionic configurations, connected with the electron transfer process and the related exchange integrals.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 18 (1996), S. 107-136 
    ISSN: 0392-6737
    Keywords: Crystal and ligand fields ; Mossbauer effect ; other γ-ray spectroscopy ; Visible and ultraviolet spectra ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Coordination compounds of transition metal ions with open-shell electron configurations may exhibit dynamic electronic-structure phenomena, depending on the nature of the coordinating ligand sphere. The change of spin state with temperature («thermal spin-crossover»), light-induced electron transfer processes leading to long-lived metastable charge and spin states (e.g., «LIESST» effect), are some of the fascinating electronic games encountered in transition metal compounds, which are presently under extensive study by chemists and physicists. Mössbauer spectroscopy plays a dominant role in the investigation of such phenomena in iron compounds, as will be demonstrated in this paper. This work will focus on selected examples of «thermal spin-crossover» in iron(II) complexes and switching between different spin states by irradiation with light of different wavelength (LIESST effect), demonstrating that Mössbauer spectroscopy besides other physical techniques proves to be a highly elegant tool for following the spin state conversion and the concomitant changes of molecular and crystal structure properties. Finally, Mössbauer emission spectroscopy, both time integral and time differential, has been employed to generate and identify long-lived excited spin states by making use of the nuclear disintegration of57Co as an intrinsic molecular light source (NIESST=nuclear decay-induced excited-spin-state trapping). Lifetime measurements by optical techniques on LIESST states and by time-differential Mössbauer coincidence spectroscopy on NIESST states prove that the relaxation pathways in the mechanisms for LIESST and NIESST are identical.
    Type of Medium: Electronic Resource
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