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1Author    I. V. Bondarev, S. A. KutenRequires cookie*
 Title    Positronium Quadrupole Interactions in Crystals  
 Abstract    It is shown that, due to the hyperfine interaction between the electron and the positron, positro­ nium atoms in a crystal can acquire an effective quadrupole moment and a tensor polarizability. In such a case the effective quadrupolar interaction with intracrystalline fields leads to a quadrupolar splitting of the triplet level of positronium and also to an anisotropy of its magnetic quenching in the presence of an external magnetic field. The possibilities of observating this anisotropy experimen­ tally are discussed. 
  Reference    Z. Naturforsch. 49a, 439—443 (1994); received December 16 1993 
  Published    1994 
  Keywords    Positronium, Quadrupole interaction, Magnetic quenching 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0439.pdf 
 Identifier    ZNA-1994-49a-0439 
 Volume    49 
2Author    H.-R Blank, M. Frank, J. Heindl, M. Kaltenhäuser, H. Köchner, W. Kreische, N. Müller, S. Porscher, T. WagnerRequires cookie*
 Title    A Simple Model to Explain 19 F-TDPAD Amplitude Characteristics  
 Abstract    Since many years the 19 F-TDPAD method (TDPAD = time differential perturbed angular distri-bution) has been used to investigate electric field gradients in fluorine compounds. In these experi-ments always a strong reduction of the observed interaction amplitudes is observed. To explain these characteristics, a simple kinematic model is suggested. 
  Reference    Z. Naturforsch. 47a, 389—394 (1992); received July 29 1991 
  Published    1992 
  Keywords    TDPAD, Quadrupole interaction, Fluorine, Perturbation amplitude, Temperature dependence 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0389.pdf 
 Identifier    ZNA-1992-47a-0389 
 Volume    47 
3Author    H. Ohki, K. Harazono, T. Erata, A. Tasaki, R. IkedaRequires cookie*
 Title    Ionic Diffusion in Cu 6 PS 5 Br Studied by 63 Cu NMR  
 Abstract    Applying 63 Cu NMR technique, we observed exchange between the nonequivalent copper sites in crystalline Cu 6 PS 5 Br, known as a member of the mineral "argyrodite". Below 200 K, where the motion of the copper (I) ion is slow, we could distinguish several nonequivalent copper sites. On increasing the temperature, the chemical exchange between the nonequivalent cation sites was seen on the "Cu NMR spectra. We could determine the activation energy for this motion to be 35 kJ mol -1 , in good agreement with the published ionic conductivity. 
  Reference    Z. Naturforsch. 48a, 1005—1008 (1993); received July 13 1993 
  Published    1993 
  Keywords    Ionic conductor, 63 Cu NMR, Quadrupole interaction 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-1005.pdf 
 Identifier    ZNA-1993-48a-1005 
 Volume    48 
4Author    DesmondC. CookRequires cookie*
 Title    Measurement of Nuclear Quadrupole Interactions using Mössbauer Spectroscopy  
 Abstract    Mössbauer spectroscopy is a useful probe for investigating nuclear quadrupole interactions. It enables the magnitude, sign and asymmetry of the electric quadrupole coupling constant to be determined. It is especially important for its ability to measure these parameters for excited nuclear states. The Mössbauer effect is used to measure excited state quadrupole moments in materials whose electric field gradient (EFG) is known. More commonly however, it is used to determine the EFG from which atomic bonding and electronic structure are determined. The technique also allows temperature dependent orientation of sublattice magnetization to be measured using the direction of the electric quadrupole coupling as a reference. 
  Reference    Z. Naturforsch. 51a, 368—372 (1996); received November 20 1995 
  Published    1996 
  Keywords    Mössbauer Effect, Electric Field Gradient, Quadrupole Interaction 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0368.pdf 
 Identifier    ZNA-1996-51a-0368 
 Volume    51 
5Author    Takahiro Ueda, Nobuo NakamuraRequires cookie*
 Title    Sb NMR and SCF-MS-Xa Studies of Quadrupole Interaction and The Electronic Structure of Mixed-Valence Compound, Cs 2 SbCl 6  
 Abstract    Cs 2 SbCl 6 is known as a typical mixed-valence compound. It crystallizes into a tetragonal space group I4 1 /amd and contains two different complex anions, Sb(III)Cl| _ and Sb(V)Clg . The dark blue color of this compound has been considered to originate from a charge transfer between the above two anions. In order to study the electronic structure of these complex anions and the existence of charge transfer between them we measured the 121 Sb NMR spectrum and carried out molecular orbital calculations on the electronic states of these anions. The 121 Sb NMR spectrum consists of two peaks at 0 and 30 kHz which can be assigned to the central transition of l21 Sb in Sb(V)Cl<~ and Sb(III)Cl| _ , respectively. The line shape analyses of the spectra led to nuclear quadrupole coupling constants of nearly zero for Sb(V)Cl7 and 4.9 ±0.5 MHz for Sb(III)Cl| at room temperature. The quadrupole coupling constant of 1 Sb(III) decreases steadily on heating. The calculations of the electronic ground state energies of both anions were calculated by the MS-Xa molecular orbital method. The calculated charge-transfer band from the A lg state of Sb(III)Clg" to the A lg state of Sb(V)Cl6 appears at 610 nm and can account for the experimental electronic spectrum, the calculated quadrupole coupling constant in Sb(III)Clg" however is far larger than the experimental one. The contribution of the charge-transferred state to the ground state is negligible and so the temperature dependence of the quadrupole coupling constant of 121 Sb(III) is attributed to an anisotropic thermal expansion of the compound. 
  Reference    Z. Naturforsch. 51a, 672—676 (1996); received October 10 1995 
  Published    1996 
  Keywords    NMR, Quadrupole interaction, Molecular orbital, Mixed valence 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0672.pdf 
 Identifier    ZNA-1996-51a-0672 
 Volume    51 
6Author    H. Nishihara, N. Kijima, S. NagataRequires cookie*
 Title    NMR of 93 Nb perturbed by Quadrupole Interaction in Quasi-One-Dimensional BaNbS 3+d  
 Abstract    Field-swept NMR spectra of y3 Nb are examined for a sample of BaNbS 2 . 96 which has a semicon-ductive temperature dependence of the resistivity at low temperature, and a sample of BaNbS 3 0 3 which has a metallic temperature dependence at low temperature. Both spectra are so-called NMR powder patterns perturbed by a quadrupole interaction with a quadrupole frequency u Q = 3e 7 qQ/2I(2I — l)/i of 2.5 [MHz]. No appreciable difference in the spectra has been observed between the two samples, suggesting that the amplitude of the conduction electron density is too small to perturb the electronic environments around the niobium atoms. The general behavior of the nuclear spin-lattice relaxation of 93 Nb in both compounds is consistent with an interpretation that the relaxation at low temperature is dominated by a Korringa mechanism and at higher temperature by a quadrupole interaction. 
  Reference    Z. Naturforsch. 55a, 359—361 (2000); received August 23 1999 
  Published    2000 
  Keywords    NMR, 93 Nb, BaNbS 3, Quadrupole Interaction 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0359.pdf 
 Identifier    ZNA-2000-55a-0359 
 Volume    55 
7Author    A. C. Junqueira, A. W. Carbonari, J.Mestnik Filho, R. N. SaxenaRequires cookie*
 Title    Electric Field Gradient at Nb Site in the Intermetallic Compounds Nb 3 X (X = AI, In, Si, Ge, Sn) Measured by PAC  
 Abstract    The electric field gradient (efg) at the Nb site in the intermetallic compounds Nb 3 X (X = Al, In, Si, Ge, Sn) was measured by the Perturbed Angular Correlation (PAC) method using the well-known gamma-gamma cascade of 133 -482 keV in lxl Ta from the ß~ decay of 1K1 Hf, substituting approximately 0.1 atom percent of Nb. The PAC results show that V zz drops by nearly 40% when X changes from Al to In, and by about 25% when X changes from Si to Ge and Sn. This behavior is most probably related to the change in the degree of sp hybridization in these compounds. The V zz values of the studied compounds do not follow the well known universal correlation for the efg's in non-cubic metals but the observed trend is well reproduced by results of ab-initio electronic structure calculations. In the case of Nb 3 Al a linear temperature dependence of the quadrupole frequencies was observed in the temperature range of 6.5 to 1210 K. 
  Reference    Z. Naturforsch. 55a, 41—14 (2000); received August 25 1999 
  Published    2000 
  Keywords    Electric Field Gradient, PAC Measurements, Nb-based Alloys, Quadrupole Interactions 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0041.pdf 
 Identifier    ZNA-2000-55a-0041 
 Volume    55 
8Author    K. Królas, M. Rams, J. WojtkowskaRequires cookie*
 Title    Quadrupole Interaction of 172 Yb and 168 Er Nuclei in the First Excited 2 + State  
 Abstract    We have measured the hyperfine interactions in YbVC>4 and YbPC>4 using 172 Yb perturbed angular correlation spectroscopy for 90 -1094 keV and 1094 -79 keV 7-7 cascades. The quadrupole interaction frequency varied with temperature from 0 to 2 GHz. Precise information was obtained from both cascades independently even using the cascade with the intermediate state of the half life as short as 1.6 ns. 
  Reference    Z. Naturforsch. 55a, 45—18 (2000); received September 11 1999 
  Published    2000 
  Keywords    Quadrupole Interaction, Perturbed Angular Correlations, 172 Yb, 16X Er, YbVCV 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0045.pdf 
 Identifier    ZNA-2000-55a-0045 
 Volume    55 
9Author    M. Dietrich, A. Burchard, D. Degering, M. Deicher, J. Kortus, R. Magerle, A. Möller, V. Samokhvalov, S. Unterricker, R. ViandenRequires cookie*
 Title    Quadrupole Interaction in Ternary Chalcopyrite Semiconductors: Experiments and Theory  
 Abstract    Electric field gradients have been measured at substitutional lattice sites in ternary semiconduc-tors using Perturbed 7-7 Angular Correlation spectroscopy (PAC). The experimental results for A I B III C 2 chalcopyrite structure compounds and • A 1I B2 C4 1 defect chalcopyrites are compared with ab-initio calculations. The latter were carried out with the WIEN code that uses the Full Poten-tial Linearized Augmented Plane Wave method within a density functional theory. The agreement between experiment and theory is in most cases very good. Furthermore, the anion displacements in AgGaX 2 -compounds (X: S, Se, Te) have been determined theoretically by determining the minimum of the total energy of the electrons in an elementary cell. 
  Reference    Z. Naturforsch. 55a, 256—260 (2000); received September 11 1999 
  Published    2000 
  Keywords    Quadrupole Interaction, Chalcopyrite Semiconductors, First Principles Calculations, Perturbed Angular Correlations, Structure Parameters 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0256.pdf 
 Identifier    ZNA-2000-55a-0256 
 Volume    55 
10Author    Takahiro Ueda, Nobuo NakamuraRequires cookie*
 Title    Nature of Hydration Water in (±)-Tris(ethylenediamine)cobalt(III) Chloride Hydrate, (±)-[Co(en) 3 ]Cl 3 -/iH 2 0, as Studied by *H, 2 H, and 17 O Solid State NMR  
 Abstract    The static and dynamics properties of hydration water molecules in (±)-[Co(en) 3 ]Cl 3 were studied by means of 'H, 2 H, and ,7 0 solid state NMR. By 'H pulsed field gradient (PFG) NMR the apparent diffusion coefficient of mobile water through a micropore along the crystalline unique c-axis was found to be 1.0 x 10~ 9 m 2 s -1 . The 2 H NMR spectrum at 141 K consists of two components, one being a Pake doublet corresponding to a quadrupole coupling constant (QCC) of (226 ± 2) kHz and an asymmetry parameter of the electric field gradient 77 of 0.08 ± 0.01, and another being a Gaussian line with a linewidth of 3.5 kHz. The 17 0 NMR spectrum at 300 K also consists of a narrow Gaussian peak and a broad powder pattern with a second order quadrupole effect corresponding to QCC = (6.3 ± 0.5) MHz and 77 = 0.55±0.02. The broad and narrow components are assigned to water molecules accommodated at general 12g positions and special 2a and 2b positions in the trigonal lattice with space group Plcl. From the ratio of the populations at these positions their potential energy difference was estimated to be between (2.7 ±0.1) and (3.5 ± 0.1) kJmol -1 . The 2 H NMR spectrum at room temperature indicates a finite quadrupole interaction which is attributable to the rapid rotation of water molecule about the molecular C 2 -axis. When the water content exceeds 2.7, the QCC is reduced sharply to (5.0 ±0.1) kHz at 285 K, suggesting that there occurs rapid rotation of water and rapid exchange of 2 H between nonequivalent positions. 
  Reference    Z. Naturforsch. 55a, 362—368 (2000); received August 23 1999 
  Published    2000 
  Keywords    (±)-[Co(en) 3 ]Cl 3, Absorbed Water, Molecular Motion, Hydrogen Bond, Quadrupole Interaction 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0362.pdf 
 Identifier    ZNA-2000-55a-0362 
 Volume    55