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'NMR' in keywords Facet   Publication Year 1992  [X]
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1992[X]
1Author    S. Lewicki, B. Szafrańska, Z. PająkRequires cookie*
 Title    Molecular Motion in Solid Tetrapropylammonium Bromide and Iodide  
 Abstract    The proton NMR second moment and spin-lattice relaxation time for tetrapropylammonium bromide and iodide have been measured over a wide temperature range. A solid-solid phase transition related to the onset of cation tumbling was found for both salts and confirmed by DTA. In the low temperature phases methyl group reorientation was evidenced. For iodide a dynamic nonequivalence of the methyl groups and the onset of ethyl groups motion was also discovered. 
  Reference    Z. Naturforsch. 47a, 1115—1118 (1992); received July 14 1992 
  Published    1992 
  Keywords    NMR, Molecular motions, Phase transitions 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-1115.pdf 
 Identifier    ZNA-1992-47a-1115 
 Volume    47 
2Author    Silvia Wigand, Tetsuo Asaji, Ryuichi Ikeda, Daiyu NakamuraRequires cookie*
 Title    Reorientational Motion of Trihalogenomethyl Groups in Organic Compounds as Studied by 35 C1 NQR and 19 F NMR Spectroscopy  
 Abstract    Trihalogenomethyl derivatives of 4-chloroacetanilide, 4-ClC6HfNHCOCCl3,4-ClC6H4NHCOCF2Cl, and 4-ClC6H4NHCOCF3 were prepared. The 35 C1 NQR and 79 F NMR spin-lattice relaxation times T1Q and T1F, respectively, of these compounds were measured at various temperatures. On heating, T1Q of the CC13 and CF2C1 groups decreased rapidly above ca. 110 and 150 K, respectively, showing the onset of reorientation of the trihalogenomethyl group about the pseudo-triad axis. The activa-tion energies were determined to be 27 and 13kJmol _1 for the CC13 and CF2C1 reorientation, respectively. The temperature dependences of the 19 F NMR T1F of the CF2C1 and CF3 groups lead to activation energies of 13 and 4.3 kJ mol~ 1 , respectively, for the same reorientations. T1F of the CF3 group observed above ca. 200 K was attributed to the spin-rotational interaction. The TIQ 1 of ring-chlorine in 4-ClC6H4NHCOCCl3 and 4-ClC6H4NHCOCF3 can be interpreted by the T" law with « = 2.2 and 1.1, respectively, whereas that of 4-ClC6H4NHCOCF2Cl by the sum of two contributions: T" law (n = 2.0) and the modulation mechanism due to the CF2C1 reorientation. 
  Reference    Z. Naturforsch. 47a, 265—273 (1992); received July 19 1991 
  Published    1992 
  Keywords    Spin-lattice relaxation, NQR, NMR, Reorientational motion 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0265.pdf 
 Identifier    ZNA-1992-47a-0265 
 Volume    47 
3Author    D. BrinkmannRequires cookie*
 Title    Probing the Electronic Structure of Y-Ba-Cu-O Superconductors by Copper NQR/NMR  
 Abstract    The paper discusses some NQR/NMR studies performed on Y-Ba-Cu-O superconductors at the University of Zürich. It is shown how the resonance methods can yield information on electronic properties of quite different character. The review deals with: (1) the temperature and pressure dependence of Cu NQR frequencies in YBa 2 Cu 4 O g (1-2-4); (2) an NQR study of the properties of Ca substituted 1-2-4; (3) the temperature dependence of the Cu Knight shifts in 1-2-4; (4) the NMR of plane Cu2 in the paramagnetic state of YBa 2 Cu 3 0 6 ; (5) the dependence on temperature, pressure and orientation of the Cu spin-lattice relaxation in 1-2-4. 
  Reference    Z. Naturforsch. 47a, 1—6 (1992); received September 20 1991 
  Published    1992 
  Keywords    NQR, NMR, High-temperature superconductors, Knight shift, Spin-lattice relaxation 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0001.pdf 
 Identifier    ZNA-1992-47a-0001 
 Volume    47 
4Author    Makoto Kaga, Tetsuo Asaji, Ryuichi Ikeda, Daiyu NakamuraRequires cookie*
 Title    Chlorine Nuclear Quadrupole Relaxation and Cationic Motion in Trimethylsulfonium Hexachloroselenate(IV): [(CH 3 ) 3 Sl 2 SeCl^  
 Abstract    The 35 C1 NQR spin-lattice and spin-spin relaxation times, 7^ and T2Q, respectively, and the 'H NMR spin-lattice relaxation time T1H at 32 and 60 MHz were determined for [(CH3j3S]2SeCl6 as functions of temperature. The rapid decrease of observed above ca. 250 K with increasing temperature was attributed to the onset of reorientation of the [SeCl6] 2 " complex anion with the activation energy £a = 42 + 5 kJ mol -1 . When cooled from ca. 250 K, T1Q showed an anomalous decrease. This 7"1Q decrease was explained by electric field gradient modulation related to some cationic motion. Possible origins of the cationic motion are discussed. 
  Reference    Z. Naturforsch. 47a, 274—276 (1992); received July 19 1991 
  Published    1992 
  Keywords    Spin-lattice relaxation, NQR, NMR, EFG modulation, Molecular motion 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0274.pdf 
 Identifier    ZNA-1992-47a-0274 
 Volume    47 
5Author    Takashige Shimizu, Tetsuo Asaji, Daiyu Nakamura, Ryuichi IkedaRequires cookie*
 Title    Uniaxial Reorientation of Octahedral Complex Anions Excited in Triethylammonium Hexachlorostannate (IV) Crystals  
 Abstract    The temperature dependence of the 35 C1 NQR spin-latticew relaxation time T1Q has been deter-mined for the three resonance lines observed in [(C2H5)3NH]2SnCl6. The higher frequency lines fade out around 150 K upon heating, whereas the lowest line shows up to room temperature no anomaly, although these three lines are assigned to chlorines belonging to the same complex anion. The T1Q values of the higher two lines decrease exponentially around the fade-out temperature, where T iq of the lowest line shows no such behavior. These results are explained by the onset of uniaxial reorientations of the octahedral complex ions by 90° about the Cl-Sn-Cl axis containing the lowest frequency chlorines. The activation energy (£J of this reorientation (22-24 kJ moP 1) is the lowest so far reportd for [SnCl6] 2-ions. £a about the other axes is 67 kJ mop 1 , indicating a remarkable anisotropic reorientation. 
  Reference    Z. Naturforsch. 47a, 283—287 (1992); received July 19 1991 
  Published    1992 
  Keywords    Spin-Lattice Relaxation, NQR, NMR, Reorientational Motion, Hydrogen Bond 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0283.pdf 
 Identifier    ZNA-1992-47a-0283 
 Volume    47 
6Author    Yoshio Kume, Maki Tokoro, Tetsuo Asaji, Ryuichi Ikeda, Daiyu NakamuraRequires cookie*
 Title    Reorientational Motion of Hydrogen Bonded Octahedral Complex Anions in Hydrazinium Hexachlorostannate(IV), (N 2 H 5 ) 2 SnCl 6 , as Studied by 35 C1 NQR Spin-Lattice Relaxation Measurements  
 Abstract    The temperature dependences of NQR frequencies and spin-lattice relaxation times, T1Q, of 35 C1 in (N2H5)2SnCl6 were measured. Four NQR signals distributed in a fairly wide frequency range were observed, the lowest-frequency line exhibiting an anomalous positive temperature coefficient. The highest-frequency line showed a steep temperature dependence. These results could be interpreted by considering the intermolecular interaction between CI and -NH2 in N2H^. Below ca. 250 K, T1Q of the upper three signals exhibited a gradual decrease upon heating, explainable by lattice vibra-tions, while a shallow Tig minimum, ascribable to the modulation of electric quadrupole interaction, was observed at ca. 11ÖK for the lowest-frequency signal. The reorientation of [SnCl6] 2 ~ was elucidated to be highly anisotropic, in that it reorients about one of the CI-Sn-Cl axes much more frequently than about the other two axes. The activation energies were determined to be 62 and 94 kj mol -1 for the respective reorientations. 
  Reference    Z. Naturforsch. 47a, 288—292 (1992); received July 17 1991 
  Published    1992 
  Keywords    Key word: Spin-Lattice Relaxation, NQR, NMR, Reorientational Motion, Hydrogen Bond 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0288.pdf 
 Identifier    ZNA-1992-47a-0288 
 Volume    47