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1994[X]
41Author    Y. Kume, T. A. Sajia, R. IkedaRequires cookie*
 Title    Low Temperature Isotope Effect in Ammonium Hexachloroselenate(IV) Studied by 35C1 NQR  
 Abstract    The temperature dependence o f the 35C1 N Q R frequency and spin-lattice relaxation time TlQ of (N H 4)2SeCl6 and (N D 4)2SeCl6 were measured from 400 K to 24.8 and 53.8 K, respectively. The disappearance of N Q R signals in the low temperature region of both salts is attributed to phase transitions. We concluded from the temperature behavior of just above the transition point that the operative mechanism o f the transition is different in these salts: The transition of (N D 4)2SeCl6 seems to be associated with rotary soft modes, while in the natural salt non-rotary soft modes seem to play an important role at the transition. 
  Reference    Z. Naturforsch. 49a, 297 (1994); received August 13 1993 
  Published    1994 
  Keywords    Isotope effect, Spin-lattice relaxation, N Q R, Phase transition, Ammonium hexa­ chloroselenate, Deuterated am m onium hexachloroselenate 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0297.pdf 
 Identifier    ZNA-1994-49a-0297 
 Volume    49 
42Author    A. J. Szabo, R.J C BrownRequires cookie*
 Title    NQR Spin-Lattice Relaxation of Re in Perrhenates  
 Abstract    The temperature dependence of the spin-lattice relaxation time Tx for the Re N Q R in K R e 0 4 , 
  Reference    Z. Naturforsch. 49a, 302 (1994); received 27 October 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0302.pdf 
 Identifier    ZNA-1994-49a-0302 
 Volume    49 
43Author    C. Forte, M. Geppi, C. A. VeraciniRequires cookie*
 Title    Study of the Molecular Dynamics from Deuterium Zeeman and Quadrupolar NMR Relaxation of 4,4'-di-n-Heptylazoxybenzene in the Nematic and Smectic A Phases  
 Abstract    The deuterium spin-lattice (T1Z) and quadrupolar (r iQ) relaxation times of the liquid crystal 4,4'-Heptyl-azoxybenzene (HAB), deuterated on the aromatic rings and the first methylene group of the chains, have been measured by means of the Jeener-Broekaert pulse sequence at two different frequencies (10 and 46.04 M Hz) and throughout the nematic and the smectic A phase. By applying suitable models, we have determined rotational and reorientational diffusion coefficients and evalu­ ated the contribution of the different m otions (internal, molecular and collective) to the relaxation. In particular we have found a non negligible contribution from order director fluctuations. A comparison between the Tlz and Ti Q measurements performed by means of Jeener-Broekaert and Wimperis pulse sequences is also shown. 
  Reference    Z. Naturforsch. 49a, 311 (1994); received August 16 1993 
  Published    1994 
  Keywords    Liquid crystal, Deuterium N M R, M olecular dynamics, Deuterium relaxation, Director fluctuation 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0311.pdf 
 Identifier    ZNA-1994-49a-0311 
 Volume    49 
44Author    T. J. BastowRequires cookie*
 Title    Materials Characterisation by Nuclear Quadrupole Interaction  
 Abstract    The power of solid state N M R to characterise solids by determining the nuclear quadrupole coupling of the constituent nuclei is demonstrated for a number of com pounds o f current interest in a materials science laboratory. Recent results are presented for the nuclei 170 , 23Na, 27A1, 39K, 71Ga, 91Zr, 93Nb, and 139La. These were derived using a variety of FT N M R techniques including static, magic angle spinning and frequency stepped spin echo N M R spectroscopy. 
  Reference    Z. Naturforsch. 49a, 320 (1994); received August 31 1993 
  Published    1994 
  Keywords    Materials, Nuclear quadrupole interaction, M ultinuclear NM R, N Q R , Materials char­ acterisation 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0320.pdf 
 Identifier    ZNA-1994-49a-0320 
 Volume    49 
45Author    J. D. Olinšek, B. Zalar, R. Blinc, N., M. R.Requires cookie*
 Title    Dynamics of Deuteron Glasses as Probed by 2 D Exchange NMR  
 Abstract    The deuteron intra-bond dynamics o f the deuteron glass phase in Rb0 68(N D 4)0 32D 2A s 0 4 has been studied by 2 D exchange N M R which extends the N M R observation window from the kHz region into the milli-Hertz region. The results show that the O -D • • • O deuterons are indeed the basic reversible tw o-position dipoles in the structure and that deuteron intra-bond exchange -and thus dipole reversal transition -occurs deeply in the glass phase well below Tg where 1 D N M R techniques observe only frozen static glassy disorder. 
  Reference    Z. Naturforsch. 49a, 329 (1994); received August 15 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0329.pdf 
 Identifier    ZNA-1994-49a-0329 
 Volume    49 
46Author    N. Obuo, N. Akam UraRequires cookie*
 Title    Nuclear Quadrupole Interaction and Ionic Dynamics in Sodium Superionic Conductors  
 Abstract    Recent work on the 23N a quadrupole interaction in the N A SIC O N family is reviewed. The applicability and the lim itation of the two-dim ensional nutation N M R to complex systems with more than one quadrupolar nuclear sites is discussed and the possibility of sodium ion exchange in som e of the N A SIC O N -type com pounds is pointed out. The microscopic mechanism of the site exchange is examined by m olecular dynamics simulation. A model potential energy function for the site exchange and /or hopping transport o f the sodium ions is proposed. It interprets qualitatively the difference between the activation energies deduced by N M R and by conductivity measurement. 
  Reference    Z. Naturforsch. 49a, 337 (1994); received O ctober 23 1993 
  Published    1994 
  Keywords    N utation N M R, Q uadrupole effect, Superionic conductor, N A SIC O N, Chemical ex­ change, M olecular dynamics 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0337.pdf 
 Identifier    ZNA-1994-49a-0337 
 Volume    49 
47Author    N. F. Peirson, J.A S Smith, D. StephensonRequires cookie*
 Title    70 Quadrupole Dips in Ammonium Persulphate  
 Abstract    The magnetic field dependence of the *H spin-lattice relaxation time in ammonium persulphate shows pronounced minima near the JH magnetic resonance frequencies of 1,200 and 2,200 kHz. These are interpreted in terms of a m odel involving cross-relaxation between *H in the N H 4 ion and 170 in natural abundance in the S2O g_ ions, the latter having a much shorter spin-lattice relaxation time. A theoretical analysis of the shape of the minima is used to derive values for the 170 quadrupole parameters. This analysis results in best estimate values for the quadrupole coupling constant of 6.75 (± 0.05) M Hz and an asymmetry of 0.30 (± 0.02). Such values are indicative o f O -H hydrogen bonding and suggest the S2O g _ ion is not undergoing rapid reorientation at temperatures below 320 K. 
  Reference    Z. Naturforsch. 49a, 345 (1994); received August 16 1993 
  Published    1994 
  Keywords    N M R, N Q R, Field cycling, Oxygen-17 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0345.pdf 
 Identifier    ZNA-1994-49a-0345 
 Volume    49 
48Author    David Stephenson, JohnA S SmithRequires cookie*
 Title    The Zeeman Effect in Quadrupole Double Resonance Spectra: Dependence of the Line Shapes on the Orientation of the Electric Field Gradient Tensor  
 Abstract    The solid effect spectrum of 1,4-dichlorobenzene was recorded at magnetic field strengths in excess of 50 G; at these field strengths Zeeman structure is seen on the 35C1 resonance. Unlike in single resonance experiments, peaks are asymmetric, and the high frequency and low frequency solid effect peaks have not the same shape. Computer calculation o f the solid effect spectrum gives peaks which show the same asymmetry as the experimental spectrum. The simulated line shapes are found to depend on the direction the principal com ponents o f the electric field gradient in the crystal framework and indicate that qyy lies in the plane o f the benzene ring. 
  Reference    Z. Naturforsch. 49a, 351 (1994); received July 23 1993 
  Published    1994 
  Keywords    35C1 quadrupole resonance, Zeeman effect, D ouble resonance, Electric field gradient 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0351.pdf 
 Identifier    ZNA-1994-49a-0351 
 Volume    49 
49Author    G. Sulzer, B. Itterm, E. Diehl, B. Fischer, H.-P Frank, E. Jäger, W. Seelinger, H.-J Stockmann, H. AckermannRequires cookie*
 Title    Temperature Dependence of Impurity Induced EFG's in Extremely Diluted CuB  
 Abstract    The temperature dependence of impurity induced EFG 's around implanted 12B ions in Cu was measured for two lattice locations using the ß-N M R method. The induced EFG at the nearest neighbouring host atoms decreases with increasing temperature for the case of 12B stopped on interstitial sites, whereas the opposite temperature behaviour was found if 12B is situated in substi­ tutional sites. 
  Reference    Z. Naturforsch. 49a, 354 (1994); received July 23 1993 
  Published    1994 
  Keywords    N M R, ß radiation detected, Cross relaxation, Electric field gradient, Temperature dependence o f EFG, Impurity induced EFG 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0354.pdf 
 Identifier    ZNA-1994-49a-0354 
 Volume    49 
50Author    M. =. Al, Cr, Ga Fe, Ti, V., Fej-J-Mjjfg Mixed, Series, M. =. Ga, H.-R Blank1, M. Frank1, M. Geiger1, J.-M Greneche2, M. Ismaier1, M. Kaltenhäuserl, R. Kapp1, W. Kreische1, M. Leblanc3, U. Lossen1, B. Z. ApRequires cookie*
 Title    Systematic Investigation of MF3 Crystalline Compounds (  
 Abstract    The electric field gradient at the fluorine site of several crystalline trifluorides was measured by means of the time differential perturbed angular distribution method. The hyperfine data (vq and rj) are systematically analyzed by taking into account the structural parameters of the crystals; tney are also compared to the results obtained by point charge calculations. 
  Reference    Z. Naturforsch. 49a, 361—366 (1994); received 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0361.pdf 
 Identifier    ZNA-1994-49a-0361 
 Volume    49 
51Author    J. Pirnat, J. Lužnik, Z. Jagličić, Z. TronteljRequires cookie*
 Title    Dehydration of Solid SnCl2(O H 2) * H 20 to SnCl2  
 Abstract    The temperature and flow rate dependence of the dehydration of SnCl2(O H 2) • H 20 , having a layered structure, into SnCl2 in a dry inert gas stream is studied. The experimental results obtained via chlorine N Q R and weight measurements are analysed in the light of the structural transforma­ tion of this compound. The mechanism of water depletion from the layered structure is discussed. 
  Reference    Z. Naturforsch. 49a, 367—372 (1994); received August 14 1993 
  Published    1994 
  Keywords    Structural transformation, Chlorine N Q R, Crystal water, Dehydration modelling, Layered structures 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0367.pdf 
 Identifier    ZNA-1994-49a-0367 
 Volume    49 
52Author    A. Trokiner, L. Le Noc, A. Yakubovskii, K. N. Mykhalyov, S. V. VerkhovskiiRequires cookie*
 Title    43Ca N M R Study of Bismuth-Based High-7C Superconductors  
 Abstract    As a first step of a study of the electronic properties of C u 0 2 planes by probing calcium nuclei in the bismuth-based high-Tc materials we report here the structural assignment of Ca N M R lines measured in 43Ca-enriched samples of n = 2 ((Bi,Pb)2Sr2CaCu2O g+x) and n = 3 ((Bi,Pb)2Sr2-Ca2C u 3O 10+Jl.) bismuth compounds. Powdered samples were investigated as well as oriented pow­ ders, achieved by uniaxial alignment of the grains in a 7T magnetic field. For the main calcium site (Ca between two C u 0 2 planes), we could determine the quadrupolar as well as the shift tensors. The results indicate that, in the same way as yttrium nuclei in YBaCuO, calcium nuclei are sensitive to the magnetic susceptibility of the metallic C u 0 2 planes. 
  Reference    Z. Naturforsch. 49a, 373—378 (1994); received 
  Published    1994 
  Keywords    43Ca N M R, High-7^ superconductors, Quadrupolar parameters, Shift parameters, Metallic state 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0373.pdf 
 Identifier    ZNA-1994-49a-0373 
 Volume    49 
53Author    M. V. Eremin, R. Markendorf, S. G. SolovjanovRequires cookie*
 Title      
 Abstract    The energy dispersion of the chain band has been determined in the framework of the Hubbard model. The results are in agreement along the T-S and T -Y lines of the Brillouin zone with photoemission data. The amount of d 3z2_r2 states is zero at y = 0 and increases to 10% at y = 1. The admixture is due to the hybridization of C u (l) dy2_z2 states with Cu(2) d 322_P2 states via apical oxygen. The effect of this admixture on the N Q R frequency of Cu(2) is discussed. 
  Reference    Z. Naturforsch. 49a, 379—384 (1994); received September 7 1993 
  Published    1994 
  Keywords    N Q R, Electron correlation, Chain band, d 3z2_r2 states, Band dispersion 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0379.pdf 
 Identifier    ZNA-1994-49a-0379 
 Volume    49 
54Author    M. V. EreminRequires cookie*
 Title    Why is the Cu(2) Asymmetry Parameter of N Q R Spectra in HTSC so Small?  
 Abstract    An explanation has been proposed for the unusual behaviour of the asymmetry parameter of N Q R spectra of Cu(2) in layered cuprates. When holes are introduced into the plane, Zhang-Rice singlets (ZRS) appear which have a strong vibronic coupling to tetragonal and orthorhombic modes. The equation for the adiabatic potential has been derived. It is shown that its minimum, correspond­ ing to orthorhombic distortions of the oxygen plaquette around the Cu(2) ions, changes under doping to tetragonal character due to the singlet exchange coupling between copper and oxygen holes. A strong interaction of ZRS via the phonon field has been found. 
  Reference    Z. Naturforsch. 49a, 385—388 (1994); received August 17 1993 
  Published    1994 
  Keywords    N Q R, Singlet correlation, Adiabatic potential, Tetragonal mode, Phonon coupling 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0385.pdf 
 Identifier    ZNA-1994-49a-0385 
 Volume    49 
55Author    J. Roos, M. Mali, D. BrinkmannRequires cookie*
 Title    Internal Magnetic Field at Ba Site in Antiferromagnetic YBa2Cu30 6 Determined by 137Ba N Q R  
 Abstract    By measuring the beat frequency of the spin-echo amplitude modulation of pulsed 137Ba N Q R, the internal magnetic field of 14.8 mT perpendicular to the tetragonal c-axis at the Ba site in the antiferromagnetic YBa2C u30 6 at 80 K was determined. Calculation of the dipole field at the Ba site 
  Reference    Z. Naturforsch. 49a, 389—390 (1994); received 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0389.pdf 
 Identifier    ZNA-1994-49a-0389 
 Volume    49 
56Author    M. Kieninger, G. Majer, A. Seeger, F. DworschakRequires cookie*
 Title    Nuclear Quadrupole Resonance Study of Copper in Electron-Irradiated YBa2Cu30 6 95  
 Abstract    N Q R of Cu in YBa2C u3O ö 95 was investigated before and after low-temperature electron irradi­ ation as well as after annealing at several distinct temperatures up to 440 K. Irradiation with 
  Reference    Z. Naturforsch. 49a, 391—394 (1994); received August 25 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0391.pdf 
 Identifier    ZNA-1994-49a-0391 
 Volume    49 
57Author    R. MarkendorfRequires cookie*
 Title    Calculated Spin-lattice Relaxation of 103Ru Compared with Low Temperature Quadrupole Orientation Measurements  
 Abstract    The spin-lattice relaxation time 7i in 103Ru has been determined on the basis of the Dirac theory and strict relativistic band structure calculations. The low temperature relaxation time T(of 103Ru in an axially symmetric quadrupole field and the quadrupole moment Q have been measured by Green and Stone using the technique of low temperature quadrupole orientation. For the usual reference value Tt T, which corresponds to relaxation in a Zeeman spectrum, they obtain 39(6) sK, which exceeds our value by 134%. This large discrepancy is attributed to the fact that the spin relaxation by direct quadrupole scattering of conduction electrons, the so-called Mitchell contribu­ tion, is dominant. According to our calculations it amounts to 81% of the total relaxation rate. This contribution could not be included in the evaluation of the experimental data. 
  Reference    Z. Naturforsch. 49a, 395—400 (1994); received September 7 1993 
  Published    1994 
  Keywords    Low temperature quadrupole orientation, Axially symmetric quadrupole field, Con­ stant of Korringa relaxation, Zeeman spectrum, Obata relation 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0395.pdf 
 Identifier    ZNA-1994-49a-0395 
 Volume    49 
58Author    M. R., R., Haruo Niki, Shoichi Tomiyoshi, Takeshi Shinohara, Mamoru Omori, Tsuyoshi Kajitani, Hiroshi Kyan, Takeshi Hamagawa, Hirotaka Odahara, N.M R Proton, M. R.Requires cookie*
 Title    Hydrogen-doped Antiferromagnetic YBa2Cu30 7_ 5H x as Studied by Proton N  
 Abstract    of the C u(l) site have been measured on the antiferromagnetic phase of a powdered sample of hydrogen-doped tetragonal YBa2C u30 6 jHq 14 between 5 and 300 K. The line width, Aa>, of *H N M R increases abruptly below 20 K. The enhancement of T2_1 and that of Tj-1 of 63Cu (1) N Q R occurs around 20 K and 40 K, respectively. The nuclear magnetization does not recover in a simple exponential manner below 80 K. The predominant mechanism governing Tx below 80 K was found to be the fluctuating magnetic field which originates from the staggered C u2 + moments in either the C u(l) oxygen-deficient layer or the C u(2)02 plane induced by the hole doping effect. These enhancements and the abrupt increase in Aco are attributed to this fluctuating magnetic field. 
  Reference    Z. Naturforsch. 49a, 401—406 (1994); received August 12 1993 
  Published    1994 
  Keywords    Antiferromagnetic materials, High-7^ superconductor, Spin-lattice relaxation time, Spin-spin relaxation time, Proton N 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0401.pdf 
 Identifier    ZNA-1994-49a-0401 
 Volume    49 
59Author    H. HaasRequires cookie*
 Title    Quadrupole Interaction at Surfaces -Nuclear Methods  
 Abstract    The measurement of the electric quadrupole interaction with nuclear techniques allows the study of monolayer coverages or even isolated atoms at surfaces and interfaces due to the inherent sensitivity of these methods. Recently electric field gradients at surface atoms have been investigated with Mößbauer Spectroscopy, Polarized Beam N M R , and Perturbed Angular Correlation (PAC). The highly sensitive PAC technique with i n In and lllm Cd sources, in particular, has been applied to several metal and semiconductor surfaces. The use of flat as well as stepped surfaces has allowed the assignment of the measured quadrupole interaction frequencies to specific surface sites. For the P d (lll) surface a particularly complete description is possible, since for five different sites (terrace adatoms, ledge adatoms, kink adatoms, ledge and terrace atoms) the field gradients and their orientation could be determined. They represent a challenging problem for understanding the electronic structure of metallic surfaces. Through the study of the temperature dependence of the different components the diffusion of the radioactive probe atoms can be followed. The data from 57Fe Mößbauer spectroscopy on iron surfaces with monolayer coverage and N M R surface studies of 7Li and 23Na at high temperatures are reviewed. An outlook for further developments of the nuclear techniques is presented, particularly in view of the variety of radioactive isotope beams available from on-line isotope separators like the IS O L D E facility at CERN. 
  Reference    Z. Naturforsch. 49a, 407—417 (1994); received December 15 1993 
  Published    1994 
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 Identifier    ZNA-1994-49a-0407 
 Volume    49 
60Author    E. A. Kravchenko, V. G. OrlovRequires cookie*
 Title    Local Magnetic Fields in some Bismuth Compounds. A Survey of Experimental Evidences  
 Abstract    The splittings observed in the 209Bi nuclear quadrupole resonances of a-Bi?0 3, in zero magnetic field, follow the typical pattern of a Zeeman perturbed N Q R spectrum. The lineshapes in Bi30 4Br also indicate a poorly resolved splitting that points to the presence of an internal magnetic field in the order of 200 G. This exceeds notably the dipole nuclear magnetic fields (about several G), but is orders of magnitude smaller than paramagnetic fields produced by unpaired electron spins. The results obtained using a S Q U ID and ^SR-technique can also be interpreted as indicative of magnetic properties not conventionally expected in such compounds. 
  Reference    Z. Naturforsch. 49a, 418—424 (1994); received December 15 1993 
  Published    1994 
  Keywords    209Bi N Q R, Internal magnetic field, Lineshape, SQ U ID, |iSR 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0418.pdf 
 Identifier    ZNA-1994-49a-0418 
 Volume    49 
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