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1986[X]
41Author    R. BlincRequires cookie*
 Title    17O NQR and the Mechanism of the Phase Transition in KH2PO4 Type H-bonded Systems  
 Abstract    17O quadrupole and 17O-proton magnetic dipolar coupling data are used to discriminate between three alternative phase transition driving mechanisms in KH2PO4 type H-bonded systems: (i) the proton order-disorder model; (ii) the P (or Se) ion order-disorder model, and (iii) the PO4 (or SeO3) orientational order-disorder model. The data for KH3(SeO3)2, CsH2PO4 and KH2PO4 definitely exclude models (ii) and (iii) and agree with the predictions of model (i). 
  Reference    Z. Naturforsch. 41a, 249 (1986); received October 12 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0249 
 Volume    41 
42Author    J. Pirnat+, J. L. Uznik+, Z. TronteljRequires cookie*
 Title    Electric Field Gradient Modulation in Incommensurate Systems X2YZ4* -*  
 Abstract    The subject of the paper is the plane wave limit of static incommensurate displacement modulation in the crystal structure, which is related to the commensurate ferrophase modulation. Using the point charge model, the corresponding electric field gradient modulation and quadrupole perturbed NMR spectra are calculated. The corrections up to the 4th order owing to the incoherent displacements of the charges in the vicinity of the resonant nucleus are considered. Comparison with the experimental data shows a reasonable agreement. 
  Reference    Z. Naturforsch. 41a, 256 (1986); received August 1 1985 
  Published    1986 
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 TEI-XML for    default:Reihe_A/41/ZNA-1986-41a-0256.pdf 
 Identifier    ZNA-1986-41a-0256 
 Volume    41 
43Author    H. Irokazu, N. Akayam, N. Obuo, N. Akam Ura, Hideaki ChiharaRequires cookie*
 Title    NQR Parameters in Incommensurate Cs2CdBr4 and Cs2HgBr4 Crystals  
 Abstract    The temperature dependence o f the 81Br spin-lattice relaxation times for Cs2CdBr4 and C s2HgBr4 was measured in the low temperature and the commensurate phases. For the com m en­ surate phase o f Cs2CdBr4 rapid shortening o f the T, o f vB ~ vc was observed on approaching the "lock-in" transition point. It is probably due to an anisotropic critical fluctuation. On the other hand, T, in the low temperature phase o f Cs2HgBr4 behaves like an order parameter but no critical decrease o f Tx was observed in the commensurate phase. 
  Reference    Z. Naturforsch. 41a, 261—264 (1986); received July 22 1985 
  Published    1986 
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 TEI-XML for    default:Reihe_A/41/ZNA-1986-41a-0261.pdf 
 Identifier    ZNA-1986-41a-0261 
 Volume    41 
44Author    J. Dolinsek, R. BlincRequires cookie*
 Title    MN Electric Field Gradient Tensors in Incommensurate |N(CH3)4 l2ZnCl4  
 Abstract    The 14N electric field gradient tensors have been determined in the paraelectric phase at 7' = 26 °C and in the incommensurate phase at r = 16 °C. The results in the incommensurate phase are typical for the "non-local" case and show the presence of two out of phase components of the modulation wave. The phase shift between the linear and the quadratic terms in the expansion of the frequency in powers of the order parameter is as large as 45°. 
  Reference    Z. Naturforsch. 41a, 265 (1986); received July 23 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0265 
 Volume    41 
45Author    Atsushi Kubo, Ryuichi Ikeda, Daiyu NakamuraRequires cookie*
 Title    Structural Phase Transition and Molecular Motion of p-Chlorobenzamide as Studied by the Temperature Variations of 35C1 NQR Frequencies, Chlorine Nuclear Quadrupolar Relaxation Times, and *H Magnetic Dipolar Relaxation Times  
 Abstract    The temperature dependences of 35Cl NQR frequencies, 35Cl (37Cl) nuclear quadrupolar relaxation times (T ,c 1q), 'H NMR absorption, and of 'H NMR relaxation times were observed for / 7-chlorobenzamide,/?-ClC6H4CONH2 and its 7V-deuterated analog. The existence of three 35Cl NQR lines already reported was confirmed for the known low temperature phase below 316 K. A single sharp 35Cl NQR line was detected in the high temperature phase up to 447 K just below the melting point 451 K. At lower temperatures, three different 35C1 T]C]Q values attributable to the fluctuation of the electric field gradient due to rotational oscillation were observed. With increasing temperature, these r lcla decreased rapidly and yielded almost the same value immediately below r tr suggesting the onset of a slow motion. I he H / , of the high temperature phase gave a T, minimum and could be explained through the 180° flip motion of the phenyl ring with an activation energy of 44 kJ m ol-1 . 
  Reference    Z. Naturforsch. 41a, 270 (1986); revised version received September 20 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0270 
 Volume    41 
46Author    I. A. Kjuntsel, V. A. Mokeeva, G. B. Soifer, I. G. ShaposhnikovRequires cookie*
 Title    A Phase Transition and Molecular Dynamics in Crystalline Q H 5CHCI2 by 35C1 NQR Investigations  
 Abstract    The NQR frequency v and the spin-lattice relaxation time T, of 35Cl nuclei in crystalline (<y,o>)-dichlorotoluene, C6H5CHC12, have been measured at temperatures above 77 K. The existence of a second-order phase transition was discovered at Tc = 94 K. At this point the low-temperature NQR spectrum consisting of five lines passes into the high-temperature doublet. The behaviour of v and Tx as functions of temperature near the critical point Tc is investigated and corresponding parameters are obtained. The NQR signals fade out about 185 K due to the reorientational motion with the potential barrier of 33.9 kJ/mole. 
  Reference    Z. Naturforsch. 41a, 275 (1986); revised version received September 29 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0275 
 Volume    41 
47Author    D. T. Amm, S. L. SegelRequires cookie*
 Title    133Cs Nuclear Quadrupole Coupling in CsOH * H2O Through the 232 K Transition  
 Abstract    The 133Cs NMR has been observed in a pseudosingle crystal of CsOH -H20 in all three solid state phases. The 133Cs quadrupole coupling constant varies almost linearly with temperature throughout the three phases (e^qQ/h = 156 ± 1 kHz at 193 K, 101 ± 1 kHz at 295 K, 36.4 ± 0.5 at 410 K). There is also a discontinuous change of (13 ± 2) kHz in the cesium coupling at the monoclinic to Hex ß transition. In contrast to previous neutron scattering experiments, which indicate significant atomic motion in the Hex a phase, the temperature dependence of the proton NMR indicates that proton diffusion occurs in the Hex ß phase. 
  Reference    Z. Naturforsch. 41a, 279 (1986); revised version received September 25 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0279 
 Volume    41 
48Author    T. J. Bastow, D. T. Amm, S. W. Segel, R. D. HeydingRequires cookie*
 Title    Low Temperature Phase of NaOD  
 Abstract    The existence of a new phase of NaOD below 160 K is reported. NQR , NMR and DTA spectra are given and preliminary X-ray powder diffraction measurements are discussed. 
  Reference    Z. Naturforsch. 41a, 283 (1986); revised version received September 25 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0283 
 Volume    41 
49Author    Maria Zdanowska-FraczekRequires cookie*
 Title    The Proton Motion Effect in the Ferroelectric Phase of NH4H(ClCH2COO)2  
 Abstract    The effects of pressure up to 3 • 102 MPa on the 35C1 NQR line splitting in the ferroelectric phase of NH4H (ClCH2COO)2, was studied from 77 K to Tc. The results are interpreted in terms of the so called pseudo-spin-lattice coupled m ode model. A correlation was found between the magnitude of the 35C1 NQ R line splitting and the pseudo-spin com ponent (S '.) (the order parameter o f the applied model). 
  Reference    Z. Naturforsch. 41a, 286 (1986); received July 22 1985 
  Published    1986 
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 TEI-XML for    default:Reihe_A/41/ZNA-1986-41a-0286.pdf 
 Identifier    ZNA-1986-41a-0286 
 Volume    41 
50Author    Mariusz Maćkowiak, Maria Zdanowska-Fną, Piotr Zek, Jan Kozioł, Stankowski, Alarich WeissRequires cookie*
 Title    High Pressure NQR Study of the Phase Transition in Anilinium Iodide  
 Abstract    The 127I NQR frequency in anilinium iodide C6H5NH3®Ie was studied at pressures up to 300 MPa and within the temperature range 77 K -290 K. With increasing pressure the order-disorder transition point Tc is shifted to higher temperatures. The pressure coefficient of the phase transition temperature amounts to dTc/dp = 4.2 x 10-2 deg M Pa-1. The pressure coefficient of the NQR frequency is negative. In addition, the 12'I nuclear quadrupole coupling constants and the respective asymmetry parameters t] were evaluated as a function of pressure. The results confirm the close connection between the mechanism of the phase transition and the dynam ics o f the N -H ® . .. 
  Reference    Z. Naturforsch. 41a, 290 (1986); revised version received October 1 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0290 
 Volume    41 
51Author    E. A. Kravchenko, V. G. Morgunov, Z.B M V V Ukhametshina, G. A. Chibrikin, YagodinRequires cookie*
 Title    Temperature Dependence of NQR Spectra and Phase Transitions in Alkali Metal Hexaiodozirconates and Hafnates (IV)  
 Abstract    H exaiodom etallates o f the type R 2M L (R = Li, N a, K, Rb, Cs; M = Zr, Hf) have been studied over a wide temperature region using l2T NQ R. They show a notable diversity o f structures. The values o f the 127I e2 Q q/li in hafnates appeared to exceed those in related zirconates by about 10%. This, together with the more positive temperature coefficients o f the NQ R spectra in zirconates is accounted for by a slightly greater 7r-character in the Z r -I than the H f -I bonds in related compounds. Several 1st and 2nd order phase transitions have been detected in N a 2MI6 (I) and R b 2MI6 (II). In (I) the high-temperature phase has a structure o f lower symmetry than the low-temperature phase, and the 1st order phase transition point reveals an extremely large range o f hysteresis. 
  Reference    Z. Naturforsch. 41a, 294—2 (1986); received July 20 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0294 
 Volume    41 
52Author    Roberto Ambrosetti, RoccoA. Ngelone ', JuanM. Urgich2Requires cookie*
 Title    A 14N FT-NQR Investigation on Solid Pyridine and Pyridine-D5  
 Abstract    The FT -N Q R spectra o f l4N in both pyridine and pyridine-D 5 show four sets o f resonance lines at — 196 °C, which disappear reversibly at — 191.5 °C and — 187 °C , respectively. This is interpreted as a phase transition, possibly o f the order-disorder type. The N Q R results can thus be reconciled with X-ray measurements at — 180 °C which suggested a single site for pyridine. The sim ilarity o f the N Q R spectra o f different samples o f both compounds, frozen and cooled with widely different procedures, suggests that the high m ultiplicity o f the N Q R spectra is not the result o f coexistence o f different crystal phases. It is shown that previously available data from IR, Raman and N Q R spectroscopies can all be put in a non-contradictory scheme. 
  Reference    Z. Naturforsch. 41a, 299 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0299 
 Volume    41 
53Author    D. T. Amm, S. L. Segel, T. J. Bastow, K. R. JeffreyRequires cookie*
 Title    Deuterium and Sodium Quadrupole Interactions in Sodium Hydroxide The Monoclinic Phase  
 Abstract    The temperature dependence of the 23NaOH Pure Quadrupole Resonance Frequency has been studied from 77 K to 550 K and shows a change in slope and a discontinuous change in frequency of 6 ± 2 kHz at the orthorhom bic to monoclinic phase transition at 505 K At 292 K the -3Na N Q R frequency is 1.778 ± 0.001 MHz, 77 < 0 .0 4 The temperature dependence of the deuterium quadrupole coupling was fit to a librating molecule model between 293 K and 570 K (QCC = 245 ± 2 kHz, rj = 0.05 ± 0 .0 1 at 293 K) and confirms that the frequency of the libration decreases in the high temperature m onoclinic phase. X-ray studies indicate that down to 10 K there are no further phase transitions in NaOH. On the other hand, it is now known that NaO D , orthorhombic at room temperature, monoclinic at high temperature, suffers another transition at 160 K to yet another monoclinic phase. 
  Reference    Z. Naturforsch. 41a, 305 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0305 
 Volume    41 
54Author    Y. M. Seo, J. Pelzl, C. DimitropoulosRequires cookie*
 Title    Temperature and Pressure Variation of the Cl-NQR in A2PbCl6-Crystals  
 Abstract    The 35C1 NQR frequency and spin-lattice relaxation rate in the compounds A2PbCl6 (A = C s, Rb, N H 4, K) have been investigated in the range 4.2 K to 500 K, and as a function of pressure at room temperature. NQR experiments conducted on (K: N H 4)2PbCl6 mixed crystals have been used to com plete the NQR-frequency versus temperature diagram of K2PbCl6, revealing two structural transitions at TC l = 358 K and at TC 2 = 333 K. 
  Reference    Z. Naturforsch. 41a, 311 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0311 
 Volume    41 
55Author    HubertS. Ch, M. Id, B. Au, R.Theodore Zafiropoulos, Wolfgang Bublak, Paul Burkert, FrankH. KöhlerRequires cookie*
 Title    High Resolution and Solid State NMR Investigations of Subvalent Gallium Compounds  
 Abstract    The 71G a NMR spectra of Ga[GaX4] melts and of solutions in benzene and other hydro­ carbons show discrete sharp Ga1 and broad Ga111 resonances. In the light of recent structure determinations, the solution Ga1 signals must be attributed to bis(arene)Ga+ complexes in which the gallium atom is rj6-bonded to the hydrocarbons. The low line widths and strong high field shifts are attributed to an almost spherical shielding of the metal nucleus by the 4 s2 electrons. Solid state 69Ga and 71Ga NMR spectra of Ga[GaCl4] crystalline powder show only Ga1 resonances. While the 71Ga1 line is rather narrow, the 6^Ga' line has a complex fine structure. Consistent with the crystal structure of Ga[GaCl4], the Ga1 ion is calculated to have a very low quadrupole coupling constant e2qQ/h = 1.7 ± 0.1 M Hz and an asymmetry parameter >7 = 0.44. Experimental and simulated line shapes (using literature models) are in satisfactory agreement, implying that the 69Ga signal splitting is due to second order quadrupolar effects for the central m = + 1/2 *=? — 1/2 transition. The analogous splitting o f the 7'Ga NMR line is too small to be detected. 
  Reference    Z. Naturforsch. 41a, 315 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0315 
 Volume    41 
56Author    Tsutomu Okuda, N.Obuhiko Tanaka, Sumio Ichiba, Koji YamRequires cookie*
 Title    Nuclear Quadrupole Resonance in Chloro-and Bromoantimonate(III) Complexes  
 Abstract    35Cl, 81Br, and 121Sb NQR spectra were observed in complexes of the type RxSbyX z with anion stoichiometries SbCl4 , SbClg-, SbBr4 , SbBr^~, SbBr^-, and Sb2Br^~. Several complexes show widely spaced halogen resonance lines and unusual temperature dependences of the NQR frequencies. These findings are accounted for in terms of a three-center four-electron bond of the X-Sb-X group and cation-anion interaction. 
  Reference    Z. Naturforsch. 41a, 319 (1986); received July 23 1985 
  Published    1986 
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 TEI-XML for    default:Reihe_A/41/ZNA-1986-41a-0319.pdf 
 Identifier    ZNA-1986-41a-0319 
 Volume    41 
57Author    A. Ishikawa, A. Sasane, Y. Mori, D. N. Akam UraRequires cookie*
 Title    Chlorine-35 NQR Studies on KNFLOo.oiKo.^hSnCl^ Mixed Crystals  
 Abstract    The temperature dependence of 35C1 NQR frequencies was measured on the mixed crystal [(N H 4)00|Kp99]2SnCl6. Two phase transitions have been located at 7"cl = 259K and J ' c2 = 252K , which are lower by 3 K than the corresponding transition temperatures of the pure K2SnCl6 crystal. The DSC experiments showed that the NH^ concentration dependence o f ?c2 almost parallels that o f Tc]. The impurity effect resulting from the inclusion of a small amount of N H f1 ions in K2SnCl6 crystals is discussed in relation to the m icroscopic viewpoint of the phase transitions. 
  Reference    Z. Naturforsch. 41a, 326 (1986); revised version received October 8 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0326 
 Volume    41 
58Author    DagmarG. Klobasa, PaulK. Burkert, Gerhard MüllerRequires cookie*
 Title    Temperature Dependence of the 1271 Quadrupole Coupling in Periodates with Alkyl-or Aryl-Substituted Cations of Main Group V  
 Abstract    127I solid state NMR studies of metaperiodates with alkyl-or aryl-substituted cations of main group V revealed second order quadrupole effects with quadrupole coupling constants in the range of 2 -7 MHz. In (C 2H 5)4PI0 4 and (C 2H 5)4AsI0 4 the 127I quadrupole coupling constants show normal temperature coefficients 5 in the order of — 10-4 K_1 for 186 K < T < 300 K. For the metaperiodates with aryl-substituted cations (C6H 5)4P+, (C 6H 5)4A s+ and (C 6H 5)4Sb+ com plicated temperature dependences o f the 127I quadrupole interaction with phase transitions and anomalous positive temperature coefficients +0.2-10~2K _1 ^ 5 . ^ + 0.8 • 10~2K_I were observed. The relevance of possible mechanisms for the anomalous temperature coefficients, like break­ down of d -p backbonding, negative pressure coefficients, charge transfer, orientational change of tne EFG-tensor axes system and influence of reorientational motions is discussed for these compounds, including results from an X-ray investigation of (C 6H 5)4A s I 0 4 and 'H-solid state NM R measurements. 
  Reference    Z. Naturforsch. 41a, 330 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0330 
 Volume    41 
59Author    T. L. Haslett, R.J C Brown, Y. S. Park, H. F. ShurvellRequires cookie*
 Title    Isotope Shifts in Ammonium Perrhenate  
 Abstract    Isotope shifts in the NQR and Raman spectra of ammonium perrhenate due to l5N and 2H substitution are reported. The effect of isotopic substitution at the nitrogen on the NQR spectrum is zero; in the Raman spectrum the translational lattice modes of the ammonium ion are clearly differentiated from the torsional modes. The effect of deuteration on the NQR frequency has been measured to high accuracy and confirms that to a moderately good approxim ation the effect of deuteration is equivalent to the application of pressure. The effect of deuteration on the lattice parameters has been measured. NQR spectra of slightly deuterated am monium perrhenate show a shoulder with a characteristic shift due to short range influence of NH3D+. 
  Reference    Z. Naturforsch. 41a, 335 (1986); received July 29 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0335 
 Volume    41 
60Author    V. Krishnan, T.V Krishna Moorthy, J. RamRequires cookie*
 Title    Pressure Dependence of Chlorine NQR in Strontium Chlorate and Barium Chlorate Monohydrate  
 Abstract    The pressure dependence of the 35C1-NQR frequencies in barium chlorate monohydrate and strontium chlorate, has been investigated up to 7000 kg cm -2. B a(C 103) 2 • H 20 shows a single 35C1-NQR line at 29.337 MHz (T = 297 K. p = 1 bar). 
  Reference    Z. Naturforsch. 41a, 338 (1986); revised version received October 12 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0338 
 Volume    41 
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