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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 697-703 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Rare-earth transition-metal magnetic materials consisting of Nd2Fe14B with small amounts of Si, produced by melt-spinning, have been studied using fluorescence extended x-ray absorption fine structure. A windowless Si(Li) solid-state detector was used to collect the Si fluorescence. These polycrystalline samples are unusual in that they are magnetically isotropic, yet have a very high remanent magnetization. The silicon atom is bonded to a single shell of iron atoms at a distance of 2.46±0.05 A(ring). The results strongly suggest that (1) Si does not segregate at the grain boundaries or cluster with other Si atoms, and that (2) Si replaces the iron atom at the "c'' site of the standard Nd2Fe14B structural model within the grains.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 1393-1398 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The 16-GeV storage ring PEP has characteristics which enable it to operate in modes with very low emittance and to accommodate very long undulators, producing synchrotron radiation at x-ray wavelengths with extremely high brightness and coherent power. Two beamlines, each illuminated by a 2-m long, 77-mm period undulator magnet, are now operational and others are planned. In parasitic operation during colliding-beam runs at 14.5 GeV, these beamlines provide photons above 10 keV with a peak brightness of about 1016 photons/(s mm2 mrad2 ) within a 0.1% bandwidth. In low-emittance tests at 7.1 GeV, horizontal emittances of about 5 nm rad were measured, which is about the same as that planned for the new third-generation x-ray sources. With a current of 15 mA at 7.1 GeV, the present undulators deliver photon beams from 2.7 to 14 keV with a peak brightness of about 1017 . Higher performance levels are expected with the implementation of longer undulators and shorter period undulators. In the longer term, because of its large circumference and long straight sections, PEP could be further developed to achieve even higher performance levels with an emittance below 1 nm rad, very long undulators and picosecond bunches, resulting in one to two orders of magnitude higher brightness and coherent power.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Nuclear and Particle Science 28 (1978), S. 33-113 
    ISSN: 0066-4243
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 604-612 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: This study tested the accuracy of the anomalous x-ray scattering technique as part of an investigation of the molecular liquid GeBr4. The differential anomalous scattering technique proved to be quite accurate, giving nearest-neighbor coordination distances and numbers correct to 0.02 A(ring) and 4%, respectively, as compared with known values. The high accuracy of the approach evidently depends on a cancellation of systematic errors when subtracting data sets at two nearby photon energies. The straightforward three-wavelength approach to determining the partial-distribution functions is quite ill conditioned and small experimental errors cause large errors in the resulting partial distribution functions. An alternate procedure, suggested by Munro, uses differences to determine the partial distribution functions (PDF's) and hence takes advantage of the cancellation of systematic errors. This approach yields Br–Br, Ge–Br, and Ge–Ge PDF's with error levels of approximately 5%–10%, 30%, and 100%, respectively. Singular value decomposition of the weighting matrix can be used to predict the relative accuracies of the three PDF's before experimentation.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 613-619 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Anomalous scattering data from 1-GeBr4 are compared with theoretical predictions and with several models. Published hard-sphere RISM calculations of the pair correlation functions accurately predict the features of the experimental distribution functions, but discrepancies between theory and experiment are larger than the experimental uncertainty. New calculations with more realistic potentials are needed. The total structure factor of 1-GeBr4 contains a prepeak which is due largely, but not exclusively, to correlations between molecular centers (i.e., germanium atoms). Modeling results indicate that there is strong interlocking of molecules in the liquid and that the Br–Br structure factor is largely determined by the packing of the halogen atoms with the germanium atoms effectively fitting in tetrahedral interstices. Models based on the monoclinic crystal of SnBr4 agree better with the liquid data than models based on the cubic crystal of c-GeBr4, suggesting that GeBr4 undergoes a change in short-range molecular packing on melting.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 279 (1976), S. 0 
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Journal of Physics and Chemistry of Solids 33 (1972), S. 1-16 
    ISSN: 0022-3697
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 15 (1962), S. 1253-1261 
    ISSN: 0001-5520
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Journal of Physics and Chemistry of Solids 24 (1963), S. 1271-1278 
    ISSN: 0022-3697
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 24 (1991), S. 598-602 
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: The tunability of synchrotron radiation was used to perform anomalous small-angle X-ray scattering (ASAXS) experiments on amorphous metal-germanium (a-MxGe100−x) alloys with the aim of detecting and characterizing composition modulation and phase separation. The combination of SAXS with the anomalous-dispersion effect allows the composition modulation to be distinguished from density fluctuations arising from voids and defects. Data gathered from a-FexGe100−x, a-WxGe100−x and a-MoxGe100−x samples in the low metal concentration regime show nanometer-scale composition modulation. In these samples the density of Ge atoms is uniform throughout. The small-angle X-ray scattering arises from fluctuations in the density of metal atoms. The position of the SAXS peak moves towards smaller values of the scattering vector with increased metal concentration indicating an increase in the correlation length of the composition fluctuations with increased metal content.
    Materialart: Digitale Medien
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