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1Author    YuA. Ossipyan, O. V. Zharikov, V. L. Matukhin, V. N. Anashkin, I. A. Safin, A. I. Pogorelcev, G. B. Teitelbaum, Yba, Cu, IodinationRequires cookie*
 Title    Cu NQR Study in a High-J c Superconductor YBa 2 Cu 3 0 6A l x  
 Abstract    NQR-spectra and nuclear relaxation of 63 Cu in ceramic samples of the Y-Ba-Cu-O system with various oxygen content have been compared with those in iodinated YBa 2 Cu 3 O eA . 
  Reference    Z. Naturforsch. 47a, 21—26 (1992); received August 8 1991 
  Published    1992 
  Keywords    NQR-spectra, Relaxation, Superconductivity 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0021.pdf 
 Identifier    ZNA-1992-47a-0021 
 Volume    47 
2Author    A. Pajzderska, J. Wąsicki, S. LewickiRequires cookie*
 Title    Molecular Motion in Tetraphenyltin Studied by NMR  
 Abstract    NMR second moment and spin-lattice relaxation times in the laboratory (60 and 25 MHz) and in the rotating frame (B { = 2.1 mT) were studied for polycrystalline tetraphenyltin Sn(C 6 H 5) 4 in a wide tem-perature range. Two kinds of motions were detected: isotropic rotation of whole molecules and reorien-tations/oscillations of phenyl rings. A dependence of the potential energy of the molecule in the crystal on the angle of the phenyl ring rotation about the Sn-C bond was obtained on the basis of atom-atom calculations. The amplitude of the ring-oscillations at 133 K was estimated as ± 7°. Below room tem-perature the magnetisation recovery is significantly non-exponential, which may be interpreted as due to the correlated motion of phenyl rings. 
  Reference    Z. Naturforsch. 54a, 488—494 (1999); received June 7 1999 
  Published    1999 
  Keywords    NMR, Relaxation, Potential Energy 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0488.pdf 
 Identifier    ZNA-1999-54a-0488 
 Volume    54 
3Author    İsmail Sert, M. Maral Sünnetçioglu, Rıza Sungur, Gökçe BingölRequires cookie*
 Title    Dynamic Nuclear Polarization Studies of TANOL/water-glycerol Solutions  
 Abstract    Dynamic Nuclear Polarization (DNP) studies of TANOL/water-glycerol solutions were per-formed at 1.53 mT. The samples have either various water-glycerol ratios at constant concen-tration or various concentrations at a constant water-glycerol ratio. The low field EPR spectra were recorded, the DNP parameters(enhancement factors, coupling constant, leakage factor) were determined, electronic relaxation times were measured. Depending on the values obtained, the interactions between nuclei and electrons are discussed. 
  Reference    Z. Naturforsch. 55a, 682—686 (2000); received April 19 2000 
  Published    2000 
  Keywords    DNP, EPR, Relaxation, Nitroxides 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0682.pdf 
 Identifier    ZNA-2000-55a-0682 
 Volume    55 
4Author    MarcoL H Gruwel1, RoderickE. WasylishenRequires cookie*
 Abstract    e u te riu m N M R S tu d y o f th e S o lid -S o lid P h a s e T ra n s itio n in P h e n e th y la m m o n iu m B ro m id e 30, 1991 Using 2H NMR, the dynamics of the cation in phenethylammonium bromide were studied in the two solid phases. Line shape and spin-lattice relaxation rate studies of the ammonium headgroups and the adajacent methylene groups indicate the onset of alkyl-chain motion prior to the first order phase transition. In the low-temperature phase the line shape and the spin-lattice relaxation rates of the -ND3 groups are consistent with C3 jumps and an activation energy of 54±4 kJ mol"1. However, in the high-temperature phase the spin-lattice relaxation studies indicate the presence of small-angle diffusion of the -ND3 groups around the C3 symmetry axis. In this phase the -CD2-groups show line shapes typical of large-amplitude two-site jumps occurring at a rate > 107 s~ l. In the low-temperature phase, at temperatures below 295 K, the -CD2-2H NMR line shapes indicate that the C-D bonds are essentially static. 
  Reference    Z. Naturforsch. 46a, 691 (1991); received March 
  Published    1991 
  Keywords    2H NMR, Phase transition, Relaxation, Molecular jumps 
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 TEI-XML for    default:Reihe_A/46/ZNA-1991-46a-0691.pdf 
 Identifier    ZNA-1991-46a-0691 
 Volume    46 
5Author    R. Julian, C. Brown, MeganE. Shortreed, AndrewJ. Szabo, BrianM. Powell, StephenN. StuartRequires cookie*
 Title    NQR and Neutron Diffraction in Scheelites  
 Abstract    Measurements of the spin-lattice relaxation time for rhenium in KRe04 and NH4Re04 are reported; relaxation rates are extremely fast due to the large quadrupole moment of Re. Calculations of the electric field gradient in KRe04 show that the EFG is a very sensitive function of the orientation of the anion in the unit cell as well as of the unit cell dimensions, and that geometrical effects make a major contribution to the temperature dependence. Neutron diffraction in these two salts has been employed to determine the temperature dependence of structural parameters over a wide range of temperature, and preliminary results are reported. 
  Reference    Z. Naturforsch. 47a, 308—312 (1992); received August 4 1991 
  Published    1992 
  Keywords    NQR, Relaxation, Electric field gradient, Neutron diffraction 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0308.pdf 
 Identifier    ZNA-1992-47a-0308 
 Volume    47 
6Author    Ch Frommen, M. Mangold, J. PeblerRequires cookie*
 Title    Magnetic Solitons in the 1-D Antiferromagnetic Chains of Li 2 Mn 0 98 Fe 0 02 F 5 and Na 2 Mn 0 98 Fe 0 0 2 F 5  
 Abstract    Measurements of the 57 Fe Mössbauer effect and magnetic susceptibility have been performed on 57 Fe-doped quasi-l-d antiferromagnetic chains of Li 2 MnF 5 and Na 2 MnFg as a function of temper-ature. The Mössbauer spectra, fitted by the Blume-Tjon model, show definite relaxation effects near the Neel temperature, which are attributed to short-range order with temperature-dependent relax-ation times. The soliton model of non-linear excitations was applied. Experimental data confirm the predicted exponential temperature dependence of the thermal excitation of moving domain walls. From the activation energies E 2 Jk 2 as a function of 1-d exchange energies J/k the local anisotropy energy D/k of —3.7(2) K was derived on the basis of sine-Gordon theory. This result is in fair agreement with —3.5(1) K previously derived from magnetic susceptibility measurements. In the light of our results there is some evidence that at low bridging angle ß % 102(5)° a phase-transition from antiferromagnetic to ferromagnetic ordering occurs. 
  Reference    Z. Naturforsch. 51a, 939—949 (1996); received February 1 1996 
  Published    1996 
  Keywords    Magnetization Exchange and Anisotropy Energy, Relaxation, Solitons 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0939.pdf 
 Identifier    ZNA-1996-51a-0939 
 Volume    51 
7Author    David Stephenson, JohnA S Smith, St Augustine, Tobago TrinidadRequires cookie*
 Title    Double Resonance Detection Using Zero Field Level Crossing  
 Abstract    Double resonance level crossing detection cannot normally be used to record transitions between the quadrupole Zeeman levels. Neither can it be used if the quadrupole resonance frequency is larger than the proton NMR frequency in high field. A simple variation of the level crossing experiment is demonstrated which allows energy to be efficiently transferred from quadrupole to proton system and hence lead to detection in these two cases. In the case of the quadrupole Zeeman levels it allows transitions between the ±\ levels to be detected in a small magnetic field, allowing measurement of the asymmetry parameter (r\) for spin 3/2 systems. This is demonstrated for the 1X B nucleus in triethanolamine borate. Detection of high frequency quadrupole transitions is demonstrated from which relaxation information is obtained. 
  Reference    Z. Naturforsch. 53a, 301—304 (1998); received October 31 1997 
  Published    1998 
  Keywords    NQR, Asymmetry Parameter, Relaxation, n B, 35 C1 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0301.pdf 
 Identifier    ZNA-1998-53a-0301 
 Volume    53 
8Author    Roman GocRequires cookie*
 Title    Monte Carlo Calculation of the Correlation Functions for Molecular Rotation -Application to NMR  
 Abstract    The Monte Carlo method for calculating correlation functions for the rotational motion of atoms is presented. This method applies to crystalline solids and allows the determination of the correlation functions for any model of rotating atoms, molecules or ions constituting the material of interest, if only its crystal structure is known. The presented method permits the calculation of the correlation functions for a whole block of unit cells, not only for a single group of particles. The described method can be employed to calculate correlation functions used in the theoretical description of NMR, dielectric or neutron diffraction experiments. As an example the correlation functions and NMR relaxation time T\ of solid benzene are calculated by the Monte Carlo method for the. 
  Reference    Z. Naturforsch. 54a, 358—364 (1999); received March 9 1999 
  Published    1999 
  Keywords    Correlation Function, Monte Carlo, NMR, Relaxation 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0358.pdf 
 Identifier    ZNA-1999-54a-0358 
 Volume    54 
9Author    R. Goc, J. Wąsicki, S. LewickiRequires cookie*
 Title    Ammonium Ions Dynamics in NH 4 Br -Proton NMR T 1 Measurements and Simulations  
 Abstract    Monte Carlo simulation of correlation functions for ammonium bromide have been carried out and the NMR relaxation times T { resulting from these functions were calculated. Results of simulations are compared to experimental values of T x measured in the temperature range 92 K to 292 K. 
  Reference    Z. Naturforsch. 54a, 689—694 (1999); received October 29 1999 
  Published    1999 
  Keywords    NMR, NH 4 Br, Relaxation, Monte Carlo, Simulation 
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 TEI-XML for    default:Reihe_A/54/ZNA-1999-54a-0689.pdf 
 Identifier    ZNA-1999-54a-0689 
 Volume    54 
10Author    David StephensonRequires cookie*
 Title    Two-dimensional Two Contact Double Resonance Spectroscopy  
 Abstract    A two-dimensional spectroscopic technique is presented. Application of the technique to de-termine all the relaxation rates for a multi-level quadrupole system is discussed along with ex-perimental requirements. Theoretical and experimental data are analyzed for the 14 N, three level, spin 1 system. The analysis shows that all three relaxation rates can be obtained from a single two-dimensional spectrum, and that only 3 peaks in the 3 x 3 two-dimensional intensity matrix are needed to completely specify the problem. The 4-level spin 3/2 system is also examined. In theory, all six relaxation rates can be independently evaluated (for a suitable system) without necessitating measurement at the low frequency Zeeman separated levels. 
  Reference    Z. Naturforsch. 55a, 79—82 (2000); received September 11 1999 
  Published    2000 
  Keywords    NQR, 14 N, Relaxation, Two-dimensional, Cross-relaxation 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0079.pdf 
 Identifier    ZNA-2000-55a-0079 
 Volume    55 
11Author    U. Schlenz, A. Dölle, H. G. HertzRequires cookie*
 Abstract    o le c u la r M o tio n in L iq u id s : T h e P a r ti a ll y R ig id M o le c u le 1,2 ,3 » 4 -T e tr a h y d r o -5 ,6 -D im e th y l-l ,4 -M e th a n o n a p h th a le n e . T e m p e r a tu r e D e p e n d e n c e o f 13C M a g n e tic R e la x a tio n a n d C o r r e la tio n T im e s Dedicated to Professor W . Müller-Warmuth on occasion of his 65 th birthday For the hydrocarbon l,2,3,4-tetrahydro-5,6-dimethyl-l,4-methanonaphthalene (5,6-Me2-THMN) 13C longitudinal relaxation times and NOE factors were measured over a wide temperature range at frequencies of 22.63 and 100.62 MHz. Additionally, 13C transversal relaxation times were mea­ sured at 100.62 MHz. The relaxation data show that the dispersion region is already reached at moderate temperatures. The experimental data were modeled by the combination of the Vogel-Fulcher-Tammann ansatz and a scaling of the dipolar coupling constant with a factor of 0.70. From the fit of the data also activation parameters of the rotational motion of the molecules were obtained. Although the molecules of 5,6-Me2-THMN have a rigid structure (except the two inter­ nally rotating methyl groups), the model of the rotational diffusion of rigid bodies does not satisfactorily describe the relaxation data. 
  Reference    Z. Naturforsch. 50a, 631—642 (1995); received December 16 1994 
  Published    1995 
  Keywords    Liquids, Rotational Diffusion, Rotational Correlation Times, 13C Nuclear Magnetic Resonance, Relaxation 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-0631.pdf 
 Identifier    ZNA-1995-50a-0631 
 Volume    50