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  • Institute of Physics  (35)
  • Springer  (28)
  • American Physical Society (APS)  (9)
  • American Institute of Physics (AIP)  (5)
  • Ovid Technologies  (5)
  • 2010-2014  (34)
  • 1985-1989  (30)
  • 1970-1974  (13)
  • 1930-1934  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3601-3603 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic configuration of trivalent Pu is nominally a 5f5 state in which there is a strong cancellation of the L (orbital) and S (spin) components in the J=5/2 ground state. This leads to small g factors and magnetic moments, and to unusual neutron magnetic form factors f(Q) with maxima at Q values greater than zero. We present here the results of form-factor measurements (taken on the polarized-neutron diffractometer at the ILL) on single crystals of PuSb, PuTe, and PuFe2. These results show that the form factor, which is a measure of the magnetization density of the 5f electrons around the Pu nucleus, is sensitive to the degree of localization of the 5f electrons. For example, in PuSb the 5f electrons are well localized and the form factor is in good agreement with the predictions of intermediate coupling and crystal-field theory. In PuTe f(Q) falls monotonically from a maximum at Q=0, indicating an almost spin-only system. This is produced by wide 5f bands, which give rise to the observed T-independent magnetic susceptibility. In PuFe2, however, a large maximum occurs in f(Q). We believe this arises from strong hybridization of the 5f and 3d Fe electrons, which leads to a reduction in the Pu orbital component.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3606-3608 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Generalized polarization analysis, in which all three components of polarization of both incident and scattered neutron beams are determined, can be used to probe fine details of magnetic structure. For instance, in certain antiferromagnetic crystals such as Cr2O3 neutrons scattered from reflections containing both nuclear and magnetic components have the direction of their polarization rotated in the plane containing the scattering vector as was demonstrated by Alperin [International Conference on Magnetism (Moscow, 1973)]. The sense of the rotation depends on whether the moments point towards the center of symmetry or away from it. The two corresponding configurations are distinguishable because the coordinating octahedra of oxygen ions are not centrosymmetric and should therefore have different energies. We have used a new technique which exploits the Meissner effect to obtain magnetic isolation to measure the rotation of the neutron polarization by the 102 and 1¯04 (hexagonal) reflections of Cr2O3 between 7 and 320 K. The results show that the lower-energy configuration is the one in which the chromium moments point towards the smaller of the two equilateral triangles of oxygen neighbors. The measured depolarizations were found not to be consistent with a simple domain model.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3748-3750 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic form factor of the 5f electrons around the Pu nucleus has been measured with neutrons. The experiment used polarized neutrons and a single crystal of weight 55 mg of PuSb. This compound, which has the NaCl crystal structure, is ferromagnetic below 67 K. The experiment was done in the ordered state with an applied field of 46 kOe. The results show that the Pu ion is trivalent; we see the maximum in f(Q) at Q(approximately-equal-to)2.5 A(ring)−1, which is the unambiguous signature of the 5f5 state. A detailed analysis shows that the ground-state wave function is close to that of a Γ8 state in intermediate coupling. The analysis makes use of the large azimuthal anisotropy (variation in magnetic scattering depending on the angle the scattering vector makes with the magnetic moment) and is not consistent with any possible Γ7 state.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 129-136 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial layers of ZnSe/ZnS have been grown by metalorganic vapor-phase epitaxy on (001)-oriented GaAs. A microstructural study of the defect content of these layers was performed using the combined techniques of scanning electron microscopy, reflection high-energy electron diffraction, transmission electron microscopy, and microdiffraction. Investigation of the epilayers in the [110] and [11¯0] orientations highlighted the strong anisotropy in the defect content of these ZnSe/ZnS layers. Microtwins were found exclusively in the [11¯0] sample orientation, while examination of the same layers along the orthogonal [110] projection revealed only misfit dislocations. The influence of the differential motion of α and β dislocations in the sphalerite structure is discussed in connection with these observations.
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 5988-5997 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutron experiments have been performed to measure the induced spin density distribution in single crystals of uranium tetrachloride at low temperature. A structural refinement has also established the atomic positions and thermal parameters at low temperature and these are in agreement with earlier studies. The spin-density distribution, determined with polarized neutrons, shows small but significant deviations from that expected from the single-ion crystal-field model. Fourier difference maps show a small depletion of the (5f) density near the U site and a small positive increase ∼1 A(ring) from the U site and principally along the shorter U–Cl bonds. We ascribe this to population of a 6d (x2−y2) orbital. No significant spin density is associated with the Cl site. Model calculations are presented which qualitatively account for the observed effect and involve electron transfer from the 5f to the 6d antibonding orbital formed as a result of a covalent interaction between the U 6d and Cl p states. This is the first direct observation of covalency in systems involving 5f 6d electrons.
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  • 6
    ISSN: 1572-8927
    Keywords: Equilibrium constant ; enthalpy change ; entropy change ; heat capacity change ; capacity change ; flow calorimetry ; high temperature ; hydrochloric acid ; acetic acid ; sodium acetate ; isocoulombic reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The aqueous reactions, {ie865-1} were studied as a function of ionic strength at 275, 300, and 320°C using a flow calorimetric technique. Log K, ΔH and ΔS values were determined from the fits of the calculated and experimental heats while ΔCp values were calculated from the variation of ΔH values with temperature. The log K and ΔH values for the first two reactions agree well with literature values at these temperatures. No previous results have been reported for the third reaction. The use of equations containing identical numbers of positive and identical numbers of negative charges on both sides of the equal sign (isocoulombic reaction principle) was applied to the log K values determined in this study. The resulting plots of log K for the isocoulombic reactions vs. I/T were approximately linear, which demonstrates that the ΔCp values for these reactions are approximately zero.
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  • 7
    ISSN: 1572-8927
    Keywords: Equilibrium constant ; enthalpy change ; entropy change ; heat ; capacity change ; flow calorimetry ; high temperature ; hydrogen sulfate ion and sodium sulfate ion formation ; isocoulombic effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The aqueous reactions, $$\begin{gathered} H^ + + SO_4^{2 - } = HSO_4^ - ,Na^ + + SO_4^{2 - } = NaSO_1^ - , \hfill \\ and H^ + + HSO_4^ - = H_2 SO_4 (aq) \hfill \\ \end{gathered} $$ were studied as a function of ionic strength(I) at 150, 175, 200, 250, 300 and 320°C using a flow calorimetric procedure. Log K, ΔH, ΔS and ΔC p values at I=0 were derived from the data at each temperature. Using these experimental values, equations describing log K, ΔH, ΔS and ΔC p at I=0 and temperatures from 150 to 320°C were derived for each system. The use of equations containing identical numbers of positive and identical numbers of negative charges on both sides of the equal sign (isocoulombic reaction principle) was evaluated as a technique for the extrapolation of log K values valid below 100°C to temperatures above 150°C. This evaluation indicated that the principle gives good estimates up to 320°C.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Computers and the humanities 6 (1972), S. 223-227 
    ISSN: 1572-8412
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Media Resources and Communication Sciences, Journalism
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 92 (1986), S. 57-70 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The igneous rocks of the Kialineq centre on the coast of East Greenland at 67°N include a number of quartz syenite and granite plutons intruded 35my BP. These are subvolcanic bodies emplaced by cauldron subsidence and with ring-dike and bell-jar form. Associated with the major intrusions is an extensive acid-basic mixed magma complex. Two-liquid structures, chilling of basic against acid magma, pillows of basic in acid, and net-veining of basic by acid magma, are superbly displayed. The basic magma was of a transitional or alkaline type and underwent varying degrees of fractionation in a regime of repeated intrusions and diverse chambers. Heterogeneous hybrid rocks intermediate between basalt and quartz syenite are strongly developed and were formed by repeated mechanical mixing of contrasting magmas. The energy for this mixing probably came in the main from cauldron-block subsidence. The quartz syenite magma, which itself fractionated towards granite, has initial 87Sr/86Sr ratios the same as the basic magma and is itself believed to be a fractionation product of alkali basalt magma.
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  • 10
    ISSN: 1359-5997
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract The hydration stoichiometry, products and kinetics of dicalcium silicate are summarized. Hydration takes a similar course to tricalcium silicate, but at a much slower rate. The differences and similarities between the two compounds are identified and discussed, and future research needs identified.
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