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61Author    I. V. Zolotaryov, A. S. Kim, P. G. NeufeldRequires cookie*
 Title    About Excitation of a Quadrupole Spin Echo  
  Reference    Z. Naturforsch. 55a, 353—354 (2000); received November 29 1999 
  Published    2000 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0353.pdf 
 Identifier    ZNA-2000-55a-0353 
 Volume    55 
62Author    Taka-Aki Nihei, Shin'. Ichi, Ishimaru, Ryuichi IkedaRequires cookie*
 Title    C1 NQR Studies of Hydrogen Transfer in Crystalline /7-Chlorobenzoic Acid  
 Abstract    35 C1 NQR frequencies and spin-lattice relaxation times 7, Q were measured inp-ClC 6 H 4 C0 2 H(PCB A) and p-ClQF^CC^DtPCBA-d,) at 77-333 K. T lQ in PCB A gave a shallow minimum of 8.0 ms at ca. 110 K, which could be explained by a double proton transfer mechanism in the carboxylic acid dimer referring to *H NMR data giving a T 1H minimum at almost the same temperature. PCBA-d, showed temperature dependent NQR frequencies quite analogous to those in PCBA, whereas their r 1Q behavi-our was quite different in its minimum value and its temperature as well as temperature gradient. These results were explained by suppressed deuteron tunnelling and the Ubbelohde effect. 
  Reference    Z. Naturforsch. 55a, 355—358 (2000); received August 27 1999 
  Published    2000 
  Keywords    CI NQR, Hydrogen-Bond, Hydrogen-transfer, Tunneling 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0355.pdf 
 Identifier    ZNA-2000-55a-0355 
 Volume    55 
63Author    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 
64Author    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 
65Author    Uwe Hoppe, Rainer Kranold, Dörte Stachel, Andrea Barz, AlexC. HannonRequires cookie*
 Title    Variation in P-O Bonding in Phosphate Glasses -A Neutron Diffraction Study  
 Abstract    Two different lengths of P-0 bonds in the P0 4 units of phosphate glasses are found by neutron diffraction experiments of high resolution in real space. The two lengths are related to bonds of the phosphorus atom with the terminal and the bridging oxygen atoms. The mean lengths and widths of both P-0 distance peaks change as a function of the glass composition. In a large range, starting from vitreous P 2 O s up to the pyrophosphate composition, the behavior of the bond lengths is compared with that in the related crystals and with that resulting from ab initio calculations. The bond lengths depend not only on the species of the participating oxygen atoms and on the number of links of the concerning P0 4 unit but also on the number of links of the neighboring P0 4 unit and on the species of the modifier cation. 
  Reference    Z. Naturforsch. 55a, 369—380 (2000); received October 6 1998 
  Published    2000 
  Keywords    Neutron Diffraction, Short-range Order, Phosphate Glasses 
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 Identifier    ZNA-2000-55a-0369 
 Volume    55 
66Author    J.Nomssi Nzali, W. HoyerRequires cookie*
 Title    X-ray Investigations of Liquid Bismuth-Copper Alloys  
 Abstract    Liquid copper, bismuth, and eleven bismuth-copper alloys were investigated at temperatures above the liquidus with X-ray diffraction. The experimental procedure was adjusted to reduce the effects of evaporation. The Faber-Ziman total structure factors S(Q) feature a splitting of the first maximum and negative values for Q around 1 A -1 in a large concentration range. The results are compared to previous neutron diffraction results by Zaiss and Steeb, to square-well potential model calculations by Gopala Rao and Satpathy and to a simple segregation model. The segregation model reproduces the features qualitatively. Partial structure factors are assessed by fitting both neutron and X-ray scattering results with reverse Monte-Carlo simulation. 
  Reference    Z. Naturforsch. 55a, 381—389 (2000); received May 29 1999 
  Published    2000 
  Keywords    Bismuth, Copper, Liquid Alloys, X-ray Diffraction, Microsegregation 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0381.pdf 
 Identifier    ZNA-2000-55a-0381 
 Volume    55 
67Author    Hideta Ishihara, Keizo Horiuchi, V. G. Krishnan, Ingrid Svoboda, Hartmut FuessRequires cookie*
 Title    Isolated versus Condensed Anion Structure VI: X-ray Structure Analysis and 81 Br NQR of Guanidinium Pentabromodicadmate(II), [C(NH 2 ) 3 ]Cd 2 Br 5 , fns-Hydrazinium Pentabromocadmate(II), [H 2 NNH 3 ] 3 CdBr 5 , and fo's-Hydrazinium Tetrabromocadmate(II)-Tetra Hydrate, [H 2 NNH 3 ] 2 CdBr 4 -4H 2 0  
 Abstract    The structure of the condensed bromocadmate anions in [C(NH 2) 3 ]Cd 2 Br 5 (1) and [H 2 NNH 3 ] 3 CdBr 5 (2) were studied at room temperature by X-ray diffraction. (1) crystallizes with double-chains bridged by Br atoms (orthorhombic, Pmmn, Z= 2, a = 1394.0(5), b = 394.5(1), c = 1086.9(5) pm). This chain structure was not described previously. (1) shows three 8 'Br NQR lines at temperatures between 77 and 323 K. Structural phase transitions take place at 283 K and at 535 K. (2) crystallizes with Br bridged zigzag-chains (monoclinic, P2[, Z=2,a = 943.1(1), b = 778.8(2), c = 942.0(2) pm, ß = 102.10(2)°) and shows a first-order phase transition around 304 K with a large thermal hysteresis. Below the transition point five 81 Br NQR lines are observed at temperatures between 122 and 304 K, and above the transition point four 81 Br NQR lines at tem-peratures between 288 and 353 K. Two 81 Br NQR lines are observed in [H 2 NNH 3 ] 2 CdBr 4 -4H 2 0 (3) at temperatures between 77 and around 320 K with positive temperature coefficients. 
  Reference    Z. Naturforsch. 55a, 390—396 (2000); received November 19 1999 
  Published    2000 
  Keywords    NQR, DSC, Crystal Structure, Phase Transition, Bromocadmate 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0390.pdf 
 Identifier    ZNA-2000-55a-0390 
 Volume    55 
68Author    Woo-Pyo HongRequires cookie*
 Title    Analytical Dark Solitary Wave Solutions for the Higher Order Nonlinear Schrödinger Equation with Cubic-quintic Terms  
 Abstract    By means of the coupled amplitude-phase method we find analytical dark solitary wave solutions for the higher order nonlinear Schrödinger equation with cubic-quintic terms describing the effects of quintic nonlinearity on the ultra-short (femtosecond) optical soliton propagation in non-Kerr media. The dark solitary wave solution exists even for the coefficients of quintic terms much larger than those of cubic terms. 
  Reference    Z. Naturforsch. 55a, 397—0 (2000); received December 8 1999 
  Published    2000 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0397.pdf 
 Identifier    ZNA-2000-55a-0397 
 Volume    55 
69Author    Sen-Yue LouRequires cookie*
 Title    High Dimensional Schwartz KP Equations  
 Abstract    The usual (2+l)-dimensional Schwartz Kadomtsev-Petviashvili (KP) equation is extended to (n+l)-dimensions. The extension is Painleve integrable in the sense that it possesses the Painleve property. A (3+l)-dimensional special one is just found when we solve a real (3+l)-dimensional KP equation approximately. 
  Reference    Z. Naturforsch. 55a, 401—404 (2000); received January 2 1999 
  Published    2000 
  Keywords    High Dimensional Integrable Models, Schwartz KP Equation, Painleve Property 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0401.pdf 
 Identifier    ZNA-2000-55a-0401 
 Volume    55 
70Author    HansH. DiebnerRequires cookie*
 Title    On the Entropy Flow between Parts of Multi-component Systems, Partial Entropies and the Implications for Observations  
 Abstract    The concept of the time dependent instantaneously occupied phase space volume is applied to multi-component systems. It allows for the investigation of entropy flows betweeen the components of the system and the evaluation of partial entropies assigned to the subsystems. We give numerical examples by means of molecular dynamics simulations of a 100-particle gas. Using a symplectic exactly reversible algorithm, a consistent and reliable evalutation of energy and entropy exchanges as well as the intake of work is achieved. The entropy flow which is related to an information flow is linked to an observational situation. This yields a further indication for the necessity of an intrinsic observer for a better understanding of the physical world. In addition, it indicates the Gödelian structure of cognition in a most serious way because only "first-principle" assumptions are made. Thereby, the paradoxical situation which is created by Jaynes' concept of an "anthropomorphic entropy" can be resolved by putting the anthropomorphic contents of thermodynamics down to an ontological basis. This is a straightforward extension of Szilard's and Brillouin's information theoretical treatment of cognition. 
  Reference    Z. Naturforsch. 55a, 405—411 (2000); received January 8 2000 
  Published    2000 
  Keywords    Information Flow, Intrinsic Observer, Phase Space Volume, Molecular Dynamics, Entropy Flow 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0405.pdf 
 Identifier    ZNA-2000-55a-0405 
 Volume    55 
71Author    Hiroyuki IshidaRequires cookie*
 Title    H NMR Study of Ionic Motions in High Temperature Solid Phases of (CH 3 NH 3 ) 2 ZnCl 4  
 Abstract    The reorientation of the tetrahedral complex anion ZnCl 4 2-and the self-diffusion of the cation in (CH 3 NH3) 2 ZnCl4 were studied by 'H NMR spin-lattice relaxation time ('H T X) experiments. In the second highest-temperature phase, the temperature dependence of *H T X observed at 8.5 MHz could be explained by a magnetic dipolar-electric quadrupolar cross relaxation between 'H and chlorine nuclei, and the activation energy of the anion motion was determined to be 105 kJ mol -1 . In the highest-temperature phase, the activation energy of the self-diffusion of the cation was determined to be 58 kJ mol -1 from the temperature and frequency dependence of 'H T X . 
  Reference    Z. Naturforsch. 55a, 412—114 (2000); received January 8 2000 
  Published    2000 
  Keywords    Nuclear Magnetic Resonance, Molecular Motion, Cross Relaxation, (C^N^^ZnCfj 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0412.pdf 
 Identifier    ZNA-2000-55a-0412 
 Volume    55 
72Author    Harald StumpfRequires cookie*
 Title    Covariant Regularization of Nonlinear Spinorfield Quantum Theories and Probability Interpretation  
 Abstract    By a decomposition theorem a higher order nonlinear spinorfield equation can be transformed into a set of first order nonlinear spinorfield equations, i. e. into an auxiliary field formulation which allows canonical quantization. The quantum dynamics of the auxiliary fields is expressed in algebraic Schrödinger representation and admits only unphysical state spaces with indefinite metric. Regularization of the classical theory is transferred into quantum field theory by a noninvertible map from the corresponding auxiliary field state space into an associated physical state space, the metric of which is positive definite. For the effective dynamics in the physical state space probability current conservation is proved, and for physical states which describe composite particle configurations the existence of the state space is demonstrated. 
  Reference    Z. Naturforsch. 55a, 415—432 (2000); received October 23 1999 
  Published    2000 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0415.pdf 
 Identifier    ZNA-2000-55a-0415 
 Volume    55 
73Author    P. Kierzkowski, B. Pranszke, A. Kowalski, M. MenzingerRequires cookie*
 Title    Electronic Energy Partitioning in the Reactions of Metastable Mg*( 3 Pj) Atoms with F 2 , Cl 2 , Br 2 ,1 2 , IC1, IBr  
 Abstract    Chemiluminescent reactions of metastable Mg*(3 Pj) atoms with F 2 , Cl 2 , Br 2 , I 2 , IC1, IBr molecules were studied in a beam-gas experiment. For all homonuclear targets the MgX(A 2 FI -X 2 X +) emission was observed, but for IC1 and IBr reactants the Mgl(A-X) emission was absent and only MgCl(A-X) or MgBr(A-X) spectra were found. In addition, for the I 2 , IBr, IC1, Br 2 reactions, broad pseudocontinua extend from above 400 nm into the infrared. These pseudocontinua are ten-tatively attributed to the Mgl, MgBr (B' 2 Z + -X 2 Z +) transition. The total attenuation cross sections, chemiluminescence cross sections and quantum yields were measured. The quantum yields are all below 5%. The results are analyzed using information theory. The low yields for the Mg* + F 2 system are explained by a barrier in the entrance channel. For other reactions the low yields are most probably caused by predissociation of the MgX*(A 2 n) products. 
  Reference    Z. Naturforsch. 55a, 433—140 (2000); received November 26 1999 
  Published    2000 
  Keywords    Chemiluminescence, Energy Transfer, Atomic Collisions, Molecular Collisions, Luminescence 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0433.pdf 
 Identifier    ZNA-2000-55a-0433 
 Volume    55 
74Author    G. Klapper, F. Lewen, S. P. Belov, G. WinnewisserRequires cookie*
 Title    Sub-Doppler Measurements and Rotational Spectrum of 13 C ls O  
 Abstract    The rotational spectrum of n C lx O has been measured up to 1 THz. The lowest rotational transitions of 1l s O (J = 2 *-1 to J = 6 *— 5) have been measured by saturation-dip spectroscopy with an experi-mental accuracy of 2 kHz. These five low J rotational transitions cover the frequency range between 209 and 628 GHz. The narrow linewidths of about 20 kHz of the saturation dips allowed to resolve the two main hyperfine components. The splitting is caused by coupling of the 1 C nuclear spin with the rotation of the molecule. The appropriate coupling constant C/(' C O) is 33.90(81) kHz. In addition we have measured in the Doppler limited mode, the line positions of the rotational tran-sitions 7 = 7*-6,7 = 8*-7, and J = 9 *-8 with accuracies of 5 kHz. We provide a set of improved con-stants together with frequency predictions up to 4.1 THz (J = 40 *-39). 
  Reference    Z. Naturforsch. 55a, 441—443 (2000); received November 29 1999 
  Published    2000 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0441.pdf 
 Identifier    ZNA-2000-55a-0441 
 Volume    55 
75Author    A. Kawski, P. Bojarski, B. KuklinskiRequires cookie*
 Title    Local Temperature of Fluorescent Centres in Polymer Films Determined from Universal Kennard-Stepanov Relation between Absorption and Fluorescence Spectra  
 Abstract    Based on the Kennard-Stepanov relation between the extinction coefficient and fluorescence inten-sity in their overlapping region, local temperatures T* are determined for several dyes and stilbene de-rivatives in PVA and PVC polymers. It is found that excitation energy excess for tf exc > v 0 . 0 causes lo-cal heating in a rigid polymer, and the temperature difference A.T= T*-Tholds during the emission pro-cess. Such a behaviour results from slow geometrical relaxation in a polymer. Excitation energy excess is also evidenced by the fact that the intensity distribution in the emission band depends slightly on the excitation wavelength. This effect is stronger for higher energy excess. 
  Reference    Z. Naturforsch. 55a, 444—448 (2000); received November 12 1999 
  Published    2000 
  Keywords    Universal Relation between Absorption and Fluorescence Spectra, Local Temperature, Polymer Fluorescent Solutions 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0444.pdf 
 Identifier    ZNA-2000-55a-0444 
 Volume    55 
76Author    Stanisław Urban, Jerzy Kędzierski, Roman DąbrowskiRequires cookie*
 Title    Analysis of the Dielectric Anisotropy of Typical Nematics with the Aid of the Maier-Meier Equations  
 Abstract    Using the experimental data on the dielectric anisotropy, density, polarizability, dipole moment, and order parameter in the nematic phase of seven typical liquid crystalline substances, the applicability of the Maier-Meier theory for the description of the dielectric properties of nematics is checked. Substanc-es with different polarity and different tendency to form associates in the nematic phase were studied. It is found that the Maier-Meier equations describe fairly well the dielectric permittivity components of nematics. The estimated values of the angle ß formed by the dipole moment with the long molecular axis are compared with those obtained in other studies. 
  Reference    Z. Naturforsch. 55a, 449—456 (2000); received December 9 1999 
  Published    2000 
  Keywords    Nematic Liquid Crystals, Dielectric Anisotropy, Maier-Meier Equations 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0449.pdf 
 Identifier    ZNA-2000-55a-0449 
 Volume    55 
77Author    Young-Dae Jung, Soo-Yong RheeRequires cookie*
 Title    Photorecombination of Electrons in Dense Plasmas  
 Abstract    The plasma screening effect on the photorecombination of free electrons, with ions in a weakly plas-ma is investigated. The recombination cross section is obtained by the principle of detailed balance with the photoionization cross section of the hydrogenic ion including the plasma screening effects on the bound and continuum states of the electron. It is found that the plasma screening effects on the recom-bination cross section are less than 11% when the Debye length (A) is greater than ten times of the Bohr radius (a.) of the hydrogenic ion with nuclear charge Z. 
  Reference    Z. Naturforsch. 55a, 457—459 (2000); received November 5 1999 
  Published    2000 
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 Identifier    ZNA-2000-55a-0457 
 Volume    55 
78Author    Mohamed Fahmy, El-SayedRequires cookie*
 Title    Hydromagnetic Instability Conditions for Viscoelastic Non-Newtonian Fluids  
 Abstract    The effect of a horizontal magnetic field and a non-Newtonian stress tensor, as described by the Wal-ters B' model, on the instability of two second order fluids of high kinematic viscosities and viscoelas-ticities is investigated. For the potentially stable configuration, it is found that the system is stable or unstable for a wavenumber range depending on the kinematic viscoelasticity. For the potentially un-stable configuration, it is found that the stability criterion is dependent on orientation and magnitude of the magnetic field which is found to stabilize a certain range of the unstable configuration related to the viscoelasticity values. The behaviour of growth rates with respect to Alfven velocities are examined analytically, and it is found that the magnetic field has a dual role on the instability problem. For the exponentially varying stratifications, the system is found to be stable or unstable for the stable and un-stable stratifications under certain physical conditions, and the growth rates are found to increase or de-crease with increasing the stratification parameter values, according to some restrictions satisfied by the chosen wavenumbers range. 
  Reference    Z. Naturforsch. 55a, 460—466 (2000); received August 31 1999 
  Published    2000 
  Keywords    Hydrodynamic Stability, Non-Newtonian Fluid Flows, Magnetohydrodynamics 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0460.pdf 
 Identifier    ZNA-2000-55a-0460 
 Volume    55 
79Author    Norberto Morgante, Paolo Ghigna, Giorgio SpinoloRequires cookie*
 Title    Hole Injection Sequence in BaCu0 2 as Seen by XANES  
 Abstract    Cu-L in XANES data collected on Bao^CuO) samples with different oxygen content are report-ed. The near-edge structures are discussed together with previous conductivity measurements, and an estimate of the hole density evolution with oxygen doping is given. The reported results give evidence of the increase with <5 of the localization of doping holes on oxygen atoms. 
  Reference    Z. Naturforsch. 55a, 467—472 (2000); received December 27 1999 
  Published    2000 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0467.pdf 
 Identifier    ZNA-2000-55a-0467 
 Volume    55 
80Author    Liuping Chen, Thomas Gross, Hans-Dietrich LüdemannRequires cookie*
 Title    The T, /7-Dependence of the Chemical Shift of the Hydroxyl Protons in Deeply Supercooled Methanol and Water  
 Abstract    The hydroxyl proton chemical shifts 6 (H-O) of supercooled methanol (7" min = 149 K) and water have been determined (7" min = 183 K), and the pressure dependence of these shifts was measured up to 200 MPa. In both compounds the downfield shift of <5 (H-O) continues down to the lowest tempera-tures reached. This result disagrees with the two state models for the hydrogen bond formation in both liquids. The isotherms ö (H 2 0) show for T< 273 K an upfield shift that becomes more pronounced with decreasing temperature. For 6 (H-O-CH^), increasingp causes at all temperatures a downshift. 
  Reference    Z. Naturforsch. 55a, 473—477 (2000); received November 11 1999 
  Published    2000 
  Keywords    NMR, Supercooling, Pressure, Methanol, Water 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0473.pdf 
 Identifier    ZNA-2000-55a-0473 
 Volume    55 
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