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  • Springer  (42)
  • Springer Nature  (1)
  • Wiley-Blackwell  (1)
  • 2005-2009  (3)
  • 1990-1994  (35)
  • 1960-1964  (6)
  • 11
    Digitale Medien
    Digitale Medien
    High—Pressure phase transition in67ZnO (1992)
    Springer
    Hyperfine interactions 70 (1992), S. 1067-1070 
    Details
    ISSN: 1572-9540
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Using a high-pressure Mössbauer spectrometer for the 93.3-keV resonance in67Zn and an X-ray diffractometer of the Guinier type67ZnO powder was investigated at pressures up to ≈19% at the phase transition. Surprisingly, the center shift (CS) of the cubic phase is by ≈20μm/s more negative than CS of the wurtzite structure. The Mössbauer data as well as theoretical cluster calculations show that the volume collapse is mainly due to the increase in coordination number of nearest-neighbour (nn) atoms. Covalency of the Zn−O bond, however, is reduced due to a≈7% increase of nn distance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02397513
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  • 12
    Digitale Medien
    Digitale Medien
    High-pressure phase transition in ZnSe (1994)
    Springer
    Hyperfine interactions 93 (1994), S. 1505-1510 
    Details
    ISSN: 1572-9540
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A high-pressure Mössbauer spectrometer for the 93.3-keV resonance in67Zn and an X-ray diffractometer of the Guinier type are used to investigate67ZnSe powder at high external pressures. At ∼ 13 GPa, a phase transition from the zinc blende to the fcc (NaCl) structure is observed. The transition is accompanied by a 15.2% decrease of the volume of the unit cell. The Lamb-Mössbauer factor (LMF) increases fromf=0.53% at ambient pressure tof=1.07% at 6.1 GPa. It thendecreases tof=0.91% as the pressure is further increased to 8.2 GPa. This behavior is investigated by lattice-dynamical calculations using an 11-parameter rigid-ion model. The decrease of the LMF at high pressures is caused by the softening of the TA phonon modes, which occurs already far below the phase transition. The s-electron density ρ(0) at the67Zn nucleus increases with reduced volume. The change of ρ(0) as well as theoretical Hartree-Fock cluster calculations show that covalency of bonding 4s/4p states of Zn and Se plays an essential role and determines the isomer shift.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02072900
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  • 13
    Digitale Medien
    Digitale Medien
    Magnetic excitations and phase transition of CsFeBr3 in an external magnetic field (1990)
    Springer
    The European physical journal 81 (1990), S. 75-82 
    Details
    ISSN: 1434-6036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In CSFeBr3 the Fe2+ ion with effective spin one has locally a singlet ground state (m=0). The antiferromagnetic interactions between neighbouring Fe-ions are too weak as compared with the anisotropy constant to introduce long range order in the absence of an external field. By inelastic neutron scattering we studied the magnetic excitations in an external magnetic field up to 5 Tesla applied along thec-axis. A linear Zeeman splitting was observed with a Landé factorg=2.4. The field renormalizes the dispersion curves in such a way that the exchange interaction has decreasing influence with increasing field. Theoretical calculations according to the excitonic model of Lindgård describe the experimental results very well. At 4.1 Tesla a phase transition appears to a commensurate long range order with a 120° arrangement of the spins in the hexagonal plane. Within the limits of experimental observation this phase transition has no influence on the dynamical behaviour. No critical phenomena could be observed. The dynamical structure factor |G j(ℚ)|2 of the lower Zeeman split modes decreases with increasing field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01454216
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  • 14
    Digitale Medien
    Digitale Medien
    Magnetic excitations of CsFeCl3 in an external magnetic field parallel to the hexagonal plane (1994)
    Springer
    The European physical journal 95 (1994), S. 13-21 
    Details
    ISSN: 1434-6036
    Schlagwort(e): 75.10.Dg ; 75.25.+z ; 75.30.Et
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In CsFeCl3 the Fe2+-ion with effective spin one has locally a singlet ground state (m s =0). The ferromagnetic interactions along thec-direction and the anti-ferromagnetic interactions perpendicular to it are too week as compared to the anisotropy to introduce longrange order in the absence of an external field. By inelastic neutron scattering we have investigated the excitation spectrum in an external magnetic field up to 6 T applied perpendicular to thec-axis. Preliminary measurements in zero field show that dipolar effects lead to a shift of the minimum of the dispersion curve away from theK-point. We show that with increasing magnetic field the whole dispersion sheet is shifted towards higher frequencies and a splitting appears. With the help of a local Hamiltonian which neglects exchange interactions between all neighbours we give a qualitative explanation of the intensity of the magnetic excitations in dependence of the magnetic field. A more sophisticated theory (RPA-diagonalisation of the Heisenberg-Hamiltonian that is used to describe the magnetic behaviour of CsFeCl3) yields — apart from a mismatch for the modes at high energy transfers — a satisfactory description of the magnetic excitations of CsFeCl3 in dependence of the magnetic field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01316838
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  • 15
    Digitale Medien
    Digitale Medien
    Temperature and magnetic field dependent correlations in the singlet ground state system CsFeBr3 (1992)
    Springer
    The European physical journal 86 (1992), S. 257-262 
    Details
    ISSN: 1434-6036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The magnetic excitations in CsFeBr3 have been measured with inelastic scattering of cold neutrons to high precision at 80 mK. The fact that the lowest frequency mode softens with decreasing temperature but stabilizes at 0.11 THz below 2.5 K is the indication that CsFeBr3 remains a SGS system forT→0. From dispersion curves measured earlier in a magnetic field along the chain axis experimental intensities were derived and in turn correlation lengths. Correlation lengths were also calculated using the new parameters for exchange and anisotropy. The experimental results and the calculations both show that the correlation lengths increase for increasing magnetic field, flatten off around the phase transformation at 4.1 Tesla with a maximum of about 35 Å and then decrease again for higher fields. No critical phenomena connected with this phase transformation could be detected. The “Mirror Mode” published earlier was found to be of spurious origin due to double scattering. It does not exist.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01313834
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  • 16
    Digitale Medien
    Digitale Medien
    Momentum distributions of projectile fragments produced in the cold and hot fragmentation of relativistic136Xe and197Au projectiles (1993)
    Springer
    The European physical journal 346 (1993), S. 43-46 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.70.Np
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The longitudinal-momentum distributions of projectile fragments from 0.8 A GeV136Xe and 1 A GeV197Au projectiles impinging on targets of beryllium and aluminium, respectively, have been measured using the projectile-fragment separator FRS at GSI. Different momentum distributions have been found for two different classes of fragmentation processes: the abundant hot fragmentation with several nucleons evaporated from the prefragments, and the rare cold fragmentation with only protons removed from the projectile, but no nucleons evaporated. The data are compared to model calculations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01290780
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  • 17
    Digitale Medien
    Digitale Medien
    Charge-changing cross sections of the neutron-rich isotopes8,9,11Li (1992)
    Springer
    The European physical journal 343 (1992), S. 375-379 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 21.10.−k ; 27.20.+n ; 25.70.Np ; 21.10.Re
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Total charge-changing cross sections have been measured for8Li on C and Pb targets, for9Li on C, Al, Cu, Sn and Pb targets, as well as for11Li on C, Sn and Pb targets at about 80 MeV/nucleon. These data are compared to measured total reaction cross sections and Glauber-type calculations using Hartree-Fock density distributions. These comparisons allow to draw conclusions on the proton density distribution of the neutronrich lithium isotopes. The results show that even for the most exotic nucleus11Li the proton distribution is only very weakly influenced by the long tail in the neutron density distribution already established in several experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01289813
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  • 18
    Digitale Medien
    Digitale Medien
    Scientific goals and experiments of the project “winter precipitation at Mount Rigi”: An overview (1993)
    Springer
    Water, air & soil pollution 68 (1993), S. 1-14 
    Details
    ISSN: 1573-2932
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Wet deposition plays an important role as a mechanism for cleansing of the polluted troposphere. Fluxes of pollutants from the atmosphere to earth's surface can affect soil and aquatic ecosystems. The investigation of the pollutant incorporation into wet deposition is therefore of considerable interest for environmental research. The project “Winter precipitation at Mount Rigi” addresses the processes determining the chemical composition of wet deposition through an integrated approach considering atmospheric physical and chemical processes and their complex interactions. The investigated topics include: aerosol and gas scavenging, atmospheric chemistry (cloud water chemistry), cloud physics and dynamics. The design of the experiment, using three ground based measuring stations at the northwestern slope of the mountain, and the conceptual ideas using case study investigations are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00479389
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  • 19
    Digitale Medien
    Digitale Medien
    Phenol/cresol-formaldehyde resin characterization and contribution to product hardness (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 257-262 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Lot-to-lot variations in a phenol/cresol-formaldehyde resin were fully characterized. Resin property-product hardness relationships were examined to elucidate the cause of variable hardness in product insulators and to establish acceptance criteria for the resin. A high methylol content (φCH2OH), determined by quantitative carbon-13 nuclear magnetic resonance (13C-NMR), and a narrow molecular weight distribution (MWD), determined by size exclusion chromatography, were found necessary for resin to produce insulator meeting the minimum Shore D durometer specification of 40.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760300502
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  • 20
    Digitale Medien
    Digitale Medien
    High-resolution67Zn-Mössbauer study of oxide spinels (1992)
    Springer
    Hyperfine interactions 68 (1992), S. 161-164 
    Details
    ISSN: 1572-9540
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report on first experiments to investigate the electronic structure in the normal spinels ZnAl2O4 and ZnFe2O4 and in the inverse spinels Zn2SnO4 and Zn2TiO4 using the high-resolution67Zn-Mössbauer spectroscopy. The electric field gradient for67Zn at the B (octahedral) site in ZnAl2O4 is negative, whereas the A (tetrahedral) site remains essentially cubic, however, with a more positive center shift. ZnFe2O4 orders antiferromagnetically at ≈10K. Due to superexchange a magnetic field is observed at67Zn. In the inverse spinels short range order leads to only few (Zn,Sn) and (Zn,Ti) configurations at the octahedral sites. The s-electron densities at the67Zn sites are distinct and cover a surprisingly broad range for Zn2TiO4. This strongly suggests that d-electrons of Ti play an essential role in the chemical bond of this compound.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02396461
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