| | 41 | Author
| Yukio Hiyama | Requires cookie* | | | Title
| Multinuclear Quadrupole Resonance Studies of Biological Systems  | | | | Abstract
| We have employed multinuclear quadrupole resonance, using the field cycling technique, to study the structure of heterocyclic biomolecules. The electron density at nitrogen was investigated by the Townes-Dailey model of 14 N NQR. Large substituent effects were evident especially on the n orbitals. Electron transfer through H-bonds also affects the 14 N quadrupole interaction. Deuterium quadrupole resonance at exchangeable sites was also utilized. Since the deuterium quadrupole correlation coefficient is sensitive to the geometry of H-bonds, the intermolecular distance of the pyrrole-pyridine complex could be determined. The field cycling technique is sensitive enough to detect 14 N • • • 14 N double transitions in parabanic acid thanks to the long spin-lattice relaxation time. However in many biological systems, such as hydrates, the technique is hardly applicable because of the short proton relaxation times. In such cases the solid state NMR technique was utilized. The 2 H NMR spectrum of thymidine reveals interesting static and dynamical features of deuterium quadrupole interaction. | | | |
Reference
| Z. Naturforsch. 45a, 273—292 (1990); received August 22 1989 | | | |
Published
| 1990 | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0273.pdf | | | | Identifier
| ZNA-1990-45a-0273 | | | | Volume
| 45 | |
| 42 | Author
| 6., M. =. Sn, Pb Te, A. +., A., Dirk Borchers, Alarich Weiss | Requires cookie* | | | Title
| CI NQR Studies of Hexachlorometallates(IV) with Organic Cations, A 2 [MC1 6 1 and A'[MC1 Organic Cation | | | | Abstract
| 35 C1 NQR spectra of eleven hexachlorometallates (IV) A 2 [MC1 6 ] and A'PVICIJ, M = Sn, Te, Pb, and A + =ethylammonium, 4-picolinium, anilinium, triethylammonium, chinoxalinium, and piperi-dinium ions, and A' 2+ = 1.3-propylenediammonium ion, have been observed as a function of tem-perature. The ethylammonium hexachlorometallates(IV) (C 2 H 5 NH 3) 2 [MC1 6 ], M = Sn, Te, show a phase transition at 128.8 K and 204 K, respectively. Both compounds yield a single resonance line in their high temperature phases. In case of the stannate this single 35 C1 resonance line splits up into two lines at T c = 128.8 K, whereas for the tellurate no 35 C1 NQR signals could be found in the low temperature phase. A phase transition was also found for the 1.3-propylenediammonium hexa-chlorostannate(IV) at 287 K where the six line NQR spectrum of the low temperature phase changes into a four line spectrum. In contrast, the corresponding plumbate shows no transition. All other compounds studied contain distorted [MC1 6 ] 2_ octahedra, and therefore they yield more than one 35 C1 resonance line. The complexes have been investigated in the temperature range temperature where the lines fade out. In case of the hexachlorostannates(IV) with the ethylammo-nium, the 1.3-propylenediammonium and the triethylammonium ions, the crystal structures of the compounds are known and compared with the results of the 35 C1 NQR spectroscopy. | | | |
Reference
| Z. Naturforsch. 45a, 293—302 (1990); received July 31 1989 | | | |
Published
| 1990 | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0293.pdf | | | | Identifier
| ZNA-1990-45a-0293 | | | | Volume
| 45 | |
| 43 | Author
| A. Sasane, S. Fukumitsu, Y. Mori, D. Nakamura | Requires cookie* | | | Title
| Temperature Dependence Studies of 3 5 CI NQR Frequencies in Magnesium and Nickel Hexachlorotellurate(IV) Hexahydrates and Nickel Hexachloroiridate(IV) Hexahydrate | | | | Abstract
| The 35 C1 NQR frequencies in MgTeCl 6 • 6 H 2 0, NiTeCl 6 • 6 H 2 0, and NiIrCl 6 • 6 H 2 0 have been determined at various temperatures. These compounds form rhombohedral crystals with the space group R3, showing a single resonance line. The 35 C1 NQR frequencies of the Te(IV) complexes exhibit an unusual positive temperature coefficient. The deuterated analogs of the Te(IV) complexes show a small frequency shift at 77 K. These results are interpreted by the presene of O-H • • • CI type weak H-bonds. The resonance frequency of the Ir(IV) complex versus temperature curve shows a minimum and a maximum. This unusual temperature dependence is mainly explained by the same type of the H-bond as existing in the Te(IV) complexes. The 7r-bond formation between Ir and CI atoms is also partly responsible for the unusual temperature dependence. | | | |
Reference
| Z. Naturforsch. 45a, 303—306 (1990); received October 21 1989 | | | |
Published
| 1990 | | | |
Keywords
| 35 C1 NQR frequency, Positive temperature coefficient, H-bond, rc-bond, 1 H-2 H isotope effect | | | |
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| ZNA-1990-45a-0303 | | | | Volume
| 45 | |
| 44 | Author
| Koji Yamada, Takashi Matsui, Tomoko Tsuritani, Tsutomu Okuda, Sumio Ichiba | Requires cookie* | | | Title
| I-NQR, 119 Sn Mössbauer Effect, and Electrical Conductivity of MSnI 3 (M = K, NH 4 , Rb, Cs, and CH 3 NH 3 ) | | | | Abstract
| In a series of MSnI 3 compounds (M = K, NH 4 , Rb, Cs, CH 3 NH 3) two types of coordination around the central Sn(II) were found by 127 I-NQR and powder X-ray diffraction techniques. They are square pyramidal (for M = NH 4 , Rb) and octahedral (for M = CH 3 NH 3). CsSnI 3 , on the other hand, showed a drastic structural change of the anion at 425 K from a square pyramid to a regular octahedron. Associated with this phase transition, the electrical conductivity increased from 4xlO~ 3 Scm _1 to about 10 2 S cm" 1 . This metallic modification was characterized by 127 I-NQR and 119 Sn Mössbauer spectroscopy. | | | |
Reference
| Z. Naturforsch. 45a, 307—312 (1990); received August 24 1989 in revised form October 28 1989 | | | |
Published
| 1990 | | | |
Keywords
| NQR, Mössbauer effect, Perovskite compound, Phase transition, Electrical conductivity | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0307.pdf | | | | Identifier
| ZNA-1990-45a-0307 | | | | Volume
| 45 | |
| 45 | Author
| R. Blinc | Requires cookie* | | | Title
| NQR in Dipolar and Quadrupolar Glasses | | | | Abstract
| It is shown that nuclear quadrupole resonance and quadrupole perturbed magnetic resonance represent a powerful technique to determine the local polarization distribution and its second moment, the Edwards-Anderson order parameter, in proton and deuteron glasses. For quadrupolar glasses the local orientational distribution function can be determined from the inhomogeneous NMR or NQR lineshape, thus allowing for a measurement of the quadrupolar Edwards-Anderson order parameter. The comparison of the temperature dependences of the thus obtained order parameters with theoretical predictions then allows for a discrimination between the different possible models of the glassy transition. | | | |
Reference
| Z. Naturforsch. 45a, 313—322 (1990); received August 22 1989 | | | |
Published
| 1990 | | | |
Keywords
| NQR, Glasses, Order parameters | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0313.pdf | | | | Identifier
| ZNA-1990-45a-0313 | | | | Volume
| 45 | |
| 46 | Author
| F. Milia, G. Papavassiliou, E. Giannakopoulos | Requires cookie* | | | Title
| Elementary Excitations in Order-Disorder Systems Studied by NQR | | | | Abstract
| The 35 C1 spin-lattice and spin-spin relaxation times T x and T 2 as functions of temperature and impurity concentration were analytically calculated and experimentally verified for the incommen-surate phase of [R^ _ JC (NH 4) Jt ] 2 ZnCl 4 . The results agree with the theoretical predictions for both the amplitude and Goldstone modes of fluctuations. | | | |
Reference
| Z. Naturforsch. 45a, 323—326 (1990); received September 81989 in revised form October 23 1989 | | | |
Published
| 1990 | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0323.pdf | | | | Identifier
| ZNA-1990-45a-0323 | | | | Volume
| 45 | |
| 47 | Author
| Masao Hashimoto, Akiko Shono, Yoshiyuki Mido, Haruo Niki, Hiroshi Hentona, Koichi Mano | Requires cookie* | | | Title
| Narrowing of the 3 5 CI NQR Lines of Trichloroacetamide Caused by Its Ferroelectric Phase Transition | | | | Abstract
| Dielectric measurements on single crystals and DSC of the title compound (monoclinic, space group P2 X) revealed a ferroelectric transition at ca. 355 K (AH xs 0.5 kJ mol"Powder x-ray diffraction indicated that the high temperature phase is also monoclinic and the change in volume at the transition is very small. A displacement of hydrogen atoms is considered as responsible for the appearance of ferroelectricity. The 35 C1 NQR signals at ca. 77 K were considerably broad, but a drastic narrowing took place after the compound had once experienced the phase transition. A tentative assignment of the NQR spectrum was made from a calculation of the NQR frequencies based on the CNDO/2 method. Another phase transition was evidenced by a small drift of the DSC curve and a slight anomaly of the dielectric behavior around 358 K. The present *H NMR experi-ments gave no indication of the onset of torsional motion of the NH 2 group reported to occur at ca. 210 K. | | | |
Reference
| Z. Naturforsch. 45a, 327—333 (1990); received August 26 1989 in revised form November 1 1989 | | | |
Published
| 1990 | | | |
Keywords
| NQR, Phase transition, Ferroelectricity, Hydrogen bond, Disordered structure | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0327.pdf | | | | Identifier
| ZNA-1990-45a-0327 | | | | Volume
| 45 | |
| 48 | Author
| A. E. Wolfenson, D. J. Pusiol, A. H. Brunetti, FaM A F | Requires cookie* | | | Title
| C1 NQR Study of 4,4 , -Dichlorobenzophenone | | | | Abstract
| Pulsed NQR has been used to get information about the two phase transitions (PT) in 4,4'-di-chlorobenzophenone. The measurements of the NQR spectrum and spin-lattice relaxation suggest that the PT's correspond to a normal-incommensurate and to the lock-in of a commensurate structure at lower temperature. Strong hysteresis has been observed, which could be assigned to memory effects produced by defect migrations. | | | |
Reference
| Z. Naturforsch. 45a, 334—338 (1990); received August 23 1989 in revised form November 28 1989 | | | |
Published
| 1990 | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0334.pdf | | | | Identifier
| ZNA-1990-45a-0334 | | | | Volume
| 45 | |
| 49 | Author
| Masahiko Suhara, Koichi Mano | Requires cookie* | | | Title
| NQR and Phase Transitions in Hexachlorocyclopropane Crystal | | | | Abstract
| 35 C1 NQR and DSC studies on phase transitions in hexachlorocyclopropane (HCCP), C 3 C1 6 , are reported. It is found that HCCP has three solid phases: A high temperature disordered phase (Phase I) above 301 K (no NQR spectrum was observed); a metastable phase (Phase II), which exhibited 6 NQR lines from 77 to 270 K; a low temperature phase (Phase III) in which a 24-multiplet of 35 C1 NQR lines at 77 K, the most complex multiplet spectrum ever reported was observed. DSC measurement shows a A-type transition at 301 K and a broad transition of very slow rate at 285 K. The structure and mechanism of phase transitions in HCCP crystal are discussed. | | | |
Reference
| Z. Naturforsch. 45a, 339—342 (1990); received August 23 1989 | | | |
Published
| 1990 | | | |
Keywords
| Nuclear quadrupole resonance, Phase transition, Crystal structure, Differential scan-ning calonmetry, Order-disorder transition | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0339.pdf | | | | Identifier
| ZNA-1990-45a-0339 | | | | Volume
| 45 | |
| 50 | Author
| Hiromitsu Terao, Tsutomu Okuda | Requires cookie* | | | Title
| Br and 127 I NQR and Phase Transitions in CH 3 NH 3 HgBr 3 and CH 3 NH 3 HgI 3 | | | | Abstract
| The 81 Br and 127 I NQR spectra were recorded in CH 3 NH 3 HgBr 3 and CH 3 NH 3 HgI 3 , respec-tively. In addition to a phase transition at 338 K, successive phase transitions take place at 127 + 1, 184 + 1, and 243±5 K in CH 3 NH 3 HgBr 3 . On heating, the resonance lines of CH 3 NH 3 HgI 3 disap-pear near a phase transition at 328 K and one line appears above this temperature. The temperature variations of the resonance frequencies of the terminal halogen atoms in both crystals are extraor-dinarily steep. This indicates the large amplitude molecular motions expected for the CH 3 NH 3 cations which are linked to the terminal halogen atoms through N-H • • • X type H-bonding. | | | |
Reference
| Z. Naturforsch. 45a, 343—348 (1990); received August 26 1989 in revised form November 15 1989 | | | |
Published
| 1990 | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0343.pdf | | | | Identifier
| ZNA-1990-45a-0343 | | | | Volume
| 45 | |
| 51 | Author
| J. Pirnat, J. Lužnik, Z. Trontelj, P. K. Kadaba | Requires cookie* | | | Title
| Iodine NQR and Phase Transitions in [N(CH 3 ) 4 ] 2 ZnI 4 * a | | | | Abstract
| Using a superregenerative NQR spectrometer, the temperature dependence of 127 I NQR spectra in [N(CH 3) 4 ] 2 ZnI 4 was measured between 167 and 335 K. The measurements confirm two known structural phase transitions at 219 and 257.5 K. The correspondence between the distinct regions of iodine NQR spectra and the crystal structure is discussed. The relation of [N(CH 3) 4 ] 2 ZnI 4 to the incommensurate family with the general formula X 2 YZ 4 and the high temperature (paraphase) crystal space group D^ (Pmcn) is studied. | | | |
Reference
| Z. Naturforsch. 45a, 349—352 (1990); received August 23 1989 in revised form 25 November 1989 | | | |
Published
| 1990 | | | |
Keywords
| NQR, phase transitions, ferroelectric, crystal structure, displacement modulation | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0349.pdf | | | | Identifier
| ZNA-1990-45a-0349 | | | | Volume
| 45 | |
| 52 | Author
| Juan Murgich, Ismardo Bonalde, JoseA. Abanero | Requires cookie* | | | Title
| N Nuclear Quadrupole Resonance Study of the Phase Transitions of Ba[Fe(CN) 5 N0] -3H 2 0 | | | | Abstract
| The 14 N nuclear quadrupole resonance (NQR) of the cyanides in Ba[Fe(CN) s NO] • 3H 2 0 (BNP) was observed between 77 and 293 K. Phase transitions exist at 118,131 (both weakly first order) and 233 K (second order). Most of the cyanides were perturbed by the structural changes except for one of the trans cyanides that was only affected by the transition at 131 K. The mechanism of the phase transitions is interpreted in terms of soft modes resulting from the ion rearrangement produced by the slowing down of the water molecules upon cooling. A comparison of the NQR spectrum of BNP with that of Na ? [Fe(CN) 5 NO] • 3H 2 0 showed that the substitution of Na + by Ba 2 produced only minor changes in the charge distribution of the nitroprusside ion. | | | |
Reference
| Z. Naturforsch. 45a, 353—356 (1990); received August 25 1989 | | | |
Published
| 1990 | | | |
Keywords
| Magnetic Resonance (NQR), Nitroprussides, Phase Transitions | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0353.pdf | | | | Identifier
| ZNA-1990-45a-0353 | | | | Volume
| 45 | |
| 54 | Author
| R. Leiberich, P. C. Schmidt, N. Sahoo, T. P. Das | Requires cookie* | | | Title
| Augmented Plane Wave Study of Electric Field Gradients in Non-cubic Metals | | | | Abstract
| The electric field gradient (EFG) in body-centered tetragonal Indium metal and hexagonal closed packed Beryllium metal is calculated on the basis of a full potential scalar relativistic augmented plane wave procedure. The various contributions to the EFG in simple metals are discussed. The total EFG in In metal found theoretically is equal to q theor = 2.67 x 10 21 Vm" 2 . This value agrees well with the experimental data. Using the quadrupole moment Q deduced from the hyperfine splitting of the muon X-ray spectra one gets g exp = 2.46 x 10 21 Vm" 2 . The valence electrons of Indium give a direct contribution of q fl = 2.72 x 10 21 Vm" 2 , whereas the direct ionic contribution q ion is much smaller and has opposite sign: q ion = —0.01 x 10 21 Vm" 2 . There is a small net shielding contribution of q sh = —0.03 x 10 21 Vm -2 to the EFG composed of the ionic contribution g sh ion = -0.39 x 10 21 Vm" 2 and the valence electron contribution q sh ve = 0.36 x 10 21 Vm" 2 . | | | |
Reference
| Z. Naturforsch. 45a, 368—374 (1990); received October 11 1989 | | | |
Published
| 1990 | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0368.pdf | | | | Identifier
| ZNA-1990-45a-0368 | | | | Volume
| 45 | |
| 56 | Author
| N. G. Fazleyev | Requires cookie* | | | Title
| Theoretical Study of the Indirect Quadrupole-Quadrupole Interactions in Metals and Alloys | | | | Abstract
| The indirect multipole interactions of nuclei and impurity paramagnetic ions in metals and alloys via conduction electrons are investigated by means of the dielectric function method. The Hamilto-nian of the indirect quadrupole-quadrupole interaction of impurity paramagnetic ions and nuclei is constructed selfconsistently, taking into account the exchange interactions and correlations of the conduction electrons as well as the antishielding effects. It is shown that the energy of these indirect quadrupole interactions of the nuclei and the paramagnetic ions decreases with the distance as R ~ 3 , oscillating with a period which is determined by the wave vector on the Fermi surface and the distance R. The influence of these indirect quadrupole-quadrupole interactions on the width and shape of the NMR lines is studied. | | | |
Reference
| Z. Naturforsch. 45a, 380—384 (1990); received August 23 1989 in revised form December 1 1989 | | | |
Published
| 1990 | | | |
Keywords
| Quadrupole, Interactions, Nuclei, Metals, Resonance | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0380.pdf | | | | Identifier
| ZNA-1990-45a-0380 | | | | Volume
| 45 | |
| 57 | Author
| W. W. Warren, R. E. Walstedt | Requires cookie* | | | Title
| NQR and NMR Studies of Spin Dynamics in High T c Superconducting Cuprates | | | | Abstract
| Recent NQR and NMR studies of Cu spin dynamics in metallic YBa 2 Cu 3 0 6+JC are reviewed. The Cu nuclear relaxation rates are shown to be inconsistent with weak correlation (band) theory and the Korringa relation, but the Cu spins retain important characteristics of itinerancy. These include pairing of the Cu d-spins in the superconducting state and strong sensitivity of the Cu spin dynamics to changes in carrier concentration associated with variation of the oxygen content. Samples of reduced oxygen content (T c = 60 K) are found to contain a high concentration of Cu + Cu(l) sites associated with "full chain-empty chain" vacancy ordering. These samples also exhibit remarkable precursive suppression of planar Cu(2) nuclear relaxation above T c . | | | |
Reference
| Z. Naturforsch. 45a, 385—392 (1990); received October 25 1989 | | | |
Published
| 1990 | | | |
Keywords
| NMR, NQR, Nuclear relaxation, Spin fluctuations, Superconductivity | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0385.pdf | | | | Identifier
| ZNA-1990-45a-0385 | | | | Volume
| 45 | |
| 58 | Author
| D. Brinkmann | Requires cookie* | | | Title
| Cu NQR Studies of the Superconductors YBa 2 Cu 3 O x and YBa 2 Cu 4 0 8 | | | | Abstract
| The paper reviews some copper NQR studies in the superconductors YBa 2 Cu 3 O x and YBa 2 Cu 4 0 8 performed at the University of Zürich. The following topics are discussed: the temperature and pressure dependence of the NQR frequencies; relation between linewidths and oxygen deficiency; the determination of the electric field gradients (EFG) and Knight shifts at the copper sites; discussion of some calculations of the EFG tensors; measurements of the various relaxation times in all phases. The results obtained in both structures are compared; possible interpretations are discussed. | | | |
Reference
| Z. Naturforsch. 45a, 393—400 (1990); received August 22 1989 | | | |
Published
| 1990 | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0393.pdf | | | | Identifier
| ZNA-1990-45a-0393 | | | | Volume
| 45 | |
| 59 | Author
| E. Lippmaa, E. Joon, I. Heinmaa, V. Miidel, A. Miller, R. Stern | Requires cookie* | | | Title
| Radio-Spectroscopic Studies of Magnetic Properties of High Temperature Superconductors | | | | Abstract
| We have performed 17 0 and 63 Cu NMR measurements in YBa 2 Cu 3 0 7 _ ä ((5% 0.15) oriented powder samples at Cu0 2 plane sites Cu(2) and 0(2, 3) in the temperature range 10-300 K. The temperature dependent Knight shift K(T) and spin lattice relaxation rate 1 -(T) of 0(2, 3) yield K 2 7"iT = const in accordance with the presence of free carriers at plane oxygen sites. A sharp decrease of T{~ 1 of Cu(2) below 120 K is associated with the opening of a gap in the spectrum of antiferromagnetic spin fluctuations of localized copper 3 d 9 electrons. The comparison of different temperature dependences of spin densities at the Cu and O sites shows the presence of two nearly independent spin systems. A close similarity of YBa 2 Cu 3 0 7 _ a with heavy fermion superconductors is discussed. | | | |
Reference
| Z. Naturforsch. 45a, 401—404 (1990); received August 26 1989 | | | |
Published
| 1990 | | | |
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| default:Reihe_A/45/ZNA-1990-45a-0401.pdf | | | | Identifier
| ZNA-1990-45a-0401 | | | | Volume
| 45 | |
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