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1986[X]
61Author    S. Sengupta, S. Rhadakrishna, R.A M ArinoRequires cookie*
 Title    Nuclear Quadrupole Resonance Studies in MICA  
 Abstract    Aluminum -27 NQ R transitions were detected in Muscovite Mica at room temperature using double resonance by level crossing (DRLC) techniques. Three lines were observed with frequencies of 572.5, 1052.0, and 1624.5 kHz. These lines are assigned to the octahedrally coordinated site, A104(0 H) 2. The corresponding quadrupole coupling constant, e^qQ/h, and asymmetry parameter, rj, are 3554.8 kHz and 0.265, respectively. The remaining tetrahedrally coordinated sites, A104, gave no discernible signal, perhaps due to the greater 27A 1 -'H distance. 
  Reference    Z. Naturforsch. 41a, 341 (1986); received August 2 1985 
  Published    1986 
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 TEI-XML for    default:Reihe_A/41/ZNA-1986-41a-0341.pdf 
 Identifier    ZNA-1986-41a-0341 
 Volume    41 
62Author    S. Elschner, J. PeterssonRequires cookie*
 Title    NMR Investigation of the Quadrupolar Glass Na(CN)xCli_x Static and Dynamic Behaviour of the CN Molecules in the Quadrupolar Glass Na(C N)xC l,_, Studied by B Na and 35C1 N M R  
 Abstract    The freezing process of the CN dumbbells in the orientational glass Na (C N)YC l!_x was studied by 23N a and 35C1 N M R for several concentrations x. The systems with x ^ 0.7 undergo structural phase transitions, whereas systems with x ;$ 0.7 stay cubic on the average down to lowest temperatures. For concentrations x % 0.65, the temperature dependences of the NMR line widths give evidence that the transition into the glass state essentially consists in a deform ation of the local potential leading to a formation of preferential directions for the orientations of the CN ions. The temperature dependence of the spin lattice relaxation tim e T, shows that the motion of the CN ions in their deformed potentials remain fast. With decreasing concentration x, the influence of the collective interactions between the CN ions become less pronounced and a gradual transition to systems with decoupled CN ions can be observed. 
  Reference    Z. Naturforsch. 41a, 343 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0343 
 Volume    41 
63Author    Catherine Bessada, AlainH. Fuchs, Alain Péneau, Henri SzwarcRequires cookie*
 Title    Glassy Crystals VI. Nitrogen-14 Quadrupole Resonance in Glassy Crystalline Thiazole  
 Abstract    Crystalline thiazole has been studied by nitrogen-14 nuclear quadrupole resonance in the 77 -206 K temperature interval that contains a glass transition at 174 K. The temperature dependences of the relaxation time T], of the frequencies and the am plitudes of the NQR signals have been determined for lines v+ and v_. N o crystal-crystal phase transition has been observed, so that the glass transition at T'% can be observed on heating and on cooling. The T, measurements have shown the existence "of a large-am plitude motion which is different from that which is "frozen" at T 'g\ it corresponds to a secondary relaxation process which is still active in the glassy crystalline phase. Further studies will attempt to assign it to a definite molecular motion. 
  Reference    Z. Naturforsch. 41a, 348 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0348 
 Volume    41 
64Author    MangalaS. Krishnan, B. C. SanctuaryRequires cookie*
 Title    A Spherical Tensor Method for Pure NQR  
 Abstract    The multipole operator technique is used to exploit the rotational invariance of the Hamiltonian. The technique and its effectiveness for the pure quadrupole hamiltonian with arbitrary asymmetry parameter are discussed for spins ^ 5/2. The time evolution of the quadrupolar alignment tensor is presented analytically for various spins. The dynamics of the full density matrix are given. 
  Reference    Z. Naturforsch. 41a, 353 (1986); revised version received September 23 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0353 
 Volume    41 
65Author    F. P. Temme, B. C. SanctuaryRequires cookie*
 Title    Symmetry Partitioning over Liouville Space for Evolution under the Anisotropic Quadrupolar Spin-Spin Interaction  
 Abstract    The structure of the anisotropic indirect quadrupolar spin-spin interaction, and its effect on the spin dynamics associated with pure NQR time-dom ain response, is considered in terms o f spherical tensor operator bases and multipole theory. The advantages of symmetry-adapting the Liouville bases is discussed for I S 3/2 spin systems. In particular, symmetrized state space bases for the «-fold quadrupole cluster under Sn are introduced and enumerated for I = 3 /2 and n ^ 4, as an initial step in the process. Symmetrized Liouville space bases for the [A]2 problems involving [3 /2 :3 /2 ] and [5 /2 :5 /2 ] spin pairs under the group S2 are presented to illustrate the structure of the multipole calculations of the spin evolution under the specific spin-spin interaction term. Such systems are of especial interest on account of the nature of the molecular solids Br2 and I2. 
  Reference    Z. Naturforsch. 41a, 361 (1986); revised version received September 30 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0361 
 Volume    41 
66Author    N. E. Ainbinder, G. B Furman, G. E. Kibrik, A. Yu Poljakov, I. G. ShaposhnikovRequires cookie*
 Title    Relaxation Processes in NQR Multiple-Pulse Spin-Locking  
 Abstract    A theory of the spin-lattice and spin-spin relaxation processes in quadrupole spin systems with / > 1/2 in the situation of the multiple-pulse NQR spin locking is proposed for the pulse sequence MW-4. The theory is based on the assumption that for t ^ T2 the change of the spin system is a quasi-equilibrium process. Rate equations for inverse generalized temperatures are obtained and the kinetic coefficients calculated for the case of exponential correlation functions. The above assumption was confirmed for some substances containing the 35C1 and 123Sb, and the time constant T]e characterizing the spin echo signal decay was investigated and compared with the time constant T, in the case of continuous spin locking. 
  Reference    Z. Naturforsch. 41a, 366 (1986); received July 23 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0366 
 Volume    41 
67Author    S. Towta, D. G. HughesRequires cookie*
 Title    Orientation Dependence of the Nuclear Quadrupole Spin-lattice Relaxation of 23Na in NaNO2  
 Abstract    The nuclear quadrupole relaxation probability Wx of 23Na in a single crystal of Na NO2 has been studied by applying a selective 180° pulse to the centre line and monitoring the exponential approach to equilibrium of the satellites. The orientation dependence of Wx at 170 K is similar in form to that at 298 K, indicating that the lattice motions responsible for the relaxation are similar at both temperatures. Ratios of the A/-tensor components obtained by fitting the W, data have been compared with the results of various point charge calculations. It indicates that the relaxation is primarily caused by interaction with the four nearest oxygen atoms and confirms that the NO2 groups oscillate and reorient primarily about the c axis. 
  Reference    Z. Naturforsch. 41a, 370 (1986); received July 23 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0370 
 Volume    41 
68Author    Masao Hashimoto, Masahiro Adachi, Koichi ManoRequires cookie*
 Title    Relaxation of Lattice Imperfections as Studied by Chlorine NQR  
 Abstract    The intensities, linewidths, and frequencies of 35C1 NQR signals in 6-nitro-2,4-bis(trichloro-m ethyl)-benzo[l,3]dioxine were found to vary remarkably depending on the crystallization methods and annealing. This finding was correlated to the degree of crystal disorder. For a sample obtained by slow crystallization from an ethanolic solution of the compound, the growth of the height of the NQR absorption signal due to annealing was measured as a function of the isothermal annealing time. A kinetic analysis of the growth process gave an activation energy of approx. 110 kJ/mole for the relaxation process of the im perfection dominating the NQR signals. The dimorphism of the compound and the magnitude of the activation energy suggest the presence of misoriented molecules accompanied by vacancies in the crystal lattice of the stable phase. 
  Reference    Z. Naturforsch. 41a, 374 (1986); revised version received October 12 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0374 
 Volume    41 
69Author    CarlosA. Martin, MarianoJ. Zuriaga2Requires cookie*
 Title    The Effect of Lattice Vacancies on the NQR Parameters * *  
 Abstract    Lattice vacancy effects on NQR parameters such as the transition frequency (vQ), the spin-lattice relaxation time (T ,), and the linew idth (zfv) are studied, and expressions are proposed to describe their temperature behaviour. These expressions are applied to analyse the case of solid chlorine and values are derived for the energy and entropy associated with the creation of a vacancy and its migration energy. 
  Reference    Z. Naturforsch. 41a, 378 (1986); revised version received September 19 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0378 
 Volume    41 
70Author    J. Kasprzak, J. Lus, J. PietrzakRequires cookie*
 Title    Anomaly of Nuclear Quadrupole Relaxation in Cu20 Prepared at Low Temperatures  
 Abstract    The 63Cu and 65Cu NQR transitions in powder samples of cuprous oxide have been investigated from 77 to 500 K and at room temperature after annealing up to 1100 K Significant differences in T\ , NQR linewidth A v, and their temperature dependences were found among the samples prepared in different ways. For Cu2O samples obtained in low temperatures (below 380 K), the temperature dependence of T\ below 380 K is of activation character with Ea = 0.07 eV. These results are interpreted in terms of an electron hopping mechanism. Thermal processing of these samples permits to obtain irreversible electronic state and then the spectroscopic parameters are the same as for the samples obtained in high temperatures (above 1320 K). 
  Reference    Z. Naturforsch. 41a, 382 (1986); revised version received Septem ber 20 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0382 
 Volume    41 
71Author    R. J. Trepanier, M. A. WhiteheadRequires cookie*
 Title    Line Width Narrowing with 14N Nuclear Quadrupole Resonance Lines at 296 K and 77 K Using a High Powered Pulsed Spectrometer  
 Abstract    The dependence of the NQR line width on the RF pulse intensity and period using a continuous steady state pulse train for polycrystalline 14N compounds shows a dependence on the asymmetry parameter rj, the temperature, and the crystal structure. 
  Reference    Z. Naturforsch. 41a, 386 (1986); revised version received N ovem ber 25 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0386 
 Volume    41 
72Author    R. J. Trepanier, M. A. WhiteheadRequires cookie*
 Title    The Effect of Moisture on the N.Q.R. Relaxation of Hexamethylenetetramine at 298 K  
 Abstract    With low and and high power transient methods we have found line width narrowing of the v0 signal of HMT that contains small amounts of water at 298 K. Samples were prepared by hum idifying to moistures between 0% and 28% by weight. A minimum line width was observed around HMT : 1 H20 and is likely due to reduced dipole-dipole interactions arising from a 6.4% increase in the cell dimensions. This would account for a narrowing of 140 Hz and when offset by 50 Hz from broadening due to a smaller T, yields the experimental minimum line width. The smaller T] also indicates a reduction in the C3 rotation barrier of 2.2 kJ/mole. The v+ and v_ lines corresponding to H bonded nitrogen were found but the v0 corresponding to the R3m structure of HMT : 6 H20 was not observed. The v0_of dry HMT was seen with all samples. This implies that humidified HMT has a predominate 143 m crystal structure. When more than 1 H:0 per HMT was present the v0 line width was broadened in proportion. This is indicative of a non-uniform H20 distribution within the lattice. 
  Reference    Z. Naturforsch. 41a, 392 (1986); revised version received September 15 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0392 
 Volume    41 
73Author    B. M. AnallahRequires cookie*
 Title    Delayed Double Resonance Between Quadrupolar Levels: Observation of a Nuclear Spin Emission Signal in s-Triazine  
 Abstract    A delayed double resonance experiment was carried out using a Robinson-type continuous-wave spectrometer. The sam ple chosen was s-triazine at liquid helium temperature, where the relaxation times are o f the order o f ten hours. Line pairings between the two N itrogen -14 N Q R sites were confirmed. Emission signals from v_ transitions were observed after successively saturating first the v_ line and then the v+ line. The results are understood in terms o f a sim ple model o f spin population dynamics. 
  Reference    Z. Naturforsch. 41a, 396—3 (1986); received August 5 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0396 
 Volume    41 
74Author    Conley Stutz, KevinG. Arcia, S. Tephanie, C. OchranRequires cookie*
 Title    The Temperature Dependence of the N-14 NQR Spectrum, Relaxation Times, and Line Shapes of Cyanuric Fluoride *» *  
 Abstract    Measurements o f the N -14 N Q R spectrum, relaxation times, and line shapes as functions o f temperature o f cyanuric fluoride are reported. This material exhibits very wide lines and thus lends itself to determining the profile o f the lines from measurements o f the echo heights. The material also exhibits a phase transition similar to that found in s-triazine. The phase transition occurs at 115 ± 5 K. A comparison o f the results is m ade with those obtained previously for cyanuric chloride and s-triazine. 
  Reference    Z. Naturforsch. 41a, 399 (1986); revised version received October 17 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0399 
 Volume    41 
75Author    M. F. Orker, L. F. Reise, D. Sim, H. Saitovitch, P.R J SilvaRequires cookie*
 Title    Dynamical Quadrupole Interactions in the Hafnium Deuterium System  
 Abstract    The nuclear quadrupole interaction (NQI) at the site o f 18,Ta in H fD 2 has been investigated by tim e differential perturbed angular correlation measurements. Below 290 K the N Q I is static within a 300 nanosecond time window. Above 290 K dynamic effects related to the diffusion o f deuterium atoms start to appear, which have been analyzed in terms o f a 3-state stochastic model. Between 345 K and 500 K the jum p diffusion o f deuterium has an activation energy E .d = (0 .3 3 i |) eV. At higher temperatures the relaxation spectra suggest that transitions occur, first to the <5-phase, then to the a-phase o f the hafnium -deuterium system. At 600 K the mean residence tim e between jum ps is o f the order o f 2 nanoseconds. First measurements with H fH 2 show an isotope effect com patible with the prediction o f the classical rate theory for over-barrier diffusion. 
  Reference    Z. Naturforsch. 41a, 403 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0403 
 Volume    41 
76Author    MarianoJ. Zuriaga, CarlosA. MartinRequires cookie*
 Title    The Motion of the OH Group in p-Chlorophenol and its Influence on the 35C1 NQR Parameters*' *  
 Abstract    The 35C1 NQR transition frequencies and the spin-lattice relaxation times, T{, for both lines in p-chlorophenol have been measured in the temperature range 90-310 K. The frequency difference and the temperature derivatives for both lines clearly show the existence of two temperature intervals with distinct lattice contributions to the EFG. Similarly, 7", data show a normal behaviour due to spin-phonon interactions up to 240 K. Above this temperature T{ begins to shorten in an exponential manner. The hindered motions of the OH group are proposed as responsibles of these effects, and an activation energy of 26 kJ mol- 1 is determined. 
  Reference    Z. Naturforsch. 41a, 408 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0408 
 Volume    41 
77Author    CarlosA. Martin, MarianoJ. ZuriagaRequires cookie*
 Title    A Combined Analysis of the Cl NQR Transition Frequency and of the Specific Heat in Trichlorofluoromethane*'*  
 Abstract    The temperature dependences of the Nuclear Quadrupole Resonance (NQR) transition frequency (vq) and of the specific heat (Cp) in Trichlorofluoromethane (TCFM) are analyzed. In the analysis of vQ a procedure is developed and successfully applied that takes advantage of all the transition in the NQR spectrum on a simultaneous basis. An effective value of about 40 cm -1 is determined for the librational frequency of a TCFM molecule, and from the analysis of Cp the formation of defects is concluded, which are proposed to be lattice vacancies with a formation energy and entropy of 9.66kJ mol-1 and 29.6 Jmol-1K-1, respectively. The behaviour of Vq at the higher temperatures and the fade-out of the signals below the melting point are consistent with the presence of lattice vacancies. 
  Reference    Z. Naturforsch. 41a, 412 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0412 
 Volume    41 
78Author    B. H. Ruessink, C. M. AcleanRequires cookie*
 Title    Electric Field Nuclear M agnetic Resonance (Application to Nuclear Quadrupole Coupling)  
 Abstract    The technique of electric field NMR is outlined in terms of theoretical approach and of experimental method. As an illustration, new and recent values for quadrupole coupling constants measured in the liquid state are reported. They are compiled together with observations from the solid and the gas. A discussion concerning the differences between the phases is briefly given. Experimental results of quadrupole coupling constants for all of the three phases are still scarce. 
  Reference    Z. Naturforsch. 41a, 421 (1986) 
  Published    1986 
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 Identifier    ZNA-1986-41a-0421 
 Volume    41 
79Author    C. V. BorczyskowskiRequires cookie*
 Title    Optical Detection of NQR: Crystal Field and Matrix Effects on Halogenated Organic M olecules  
 Abstract    E lectron spin polarization o r alignm ent achieved in the excited trip let state o f organic m ole­ cules can be transferred into nu clear spin p o lariza tio n (alignm ent) d uring an optical pum ping cycle. D ue to this effect, q u a d ru p o le resonance (N Q R) investigations o f nuclei w ith concentra­ tions o f 10~5 m olar are possible in the electronic singlet g round and excited trip le t state in one and the sam e experim ent by th e applied optical p u m p in g cycle. By this conventional N M R sen­ sitivity is enhanced by several orders o f m agnitude, enabling investigations o f defect site struc­ tures in m olecular crystals. 
  Reference    Z. Naturforsch. 41a, 425 (1986); received July 22 1985 
  Published    1986 
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 Identifier    ZNA-1986-41a-0425 
 Volume    41 
80Author    R. AmbrosettiRequires cookie*
 Title    Deuterium Quadrupolar Parameters from and 2H NM R Spectra for Pyridine-d5, Benzonitrile-d5 and Chlorobenzene-d 5 Using Liquid Crystal Solvents  
 Abstract    The quadrupolar coupling constants (DQCC) and the asymmetry parameters (rj) for the ortho, meta and para deuterons in pyridine-d5, benzonitrile-d5 and chlorobenzene-d 5 were determined by NMR spectroscopy in oriented phases. The !H and 2H NMR spectra were recorded in the following solutions in liquid crystal solvents: pyridine + pyridine-ds in PCH, in ZLI 1167 and in EBBA; benzonitrile + benzonitrile-ds and chlorobenzene + chlorobenzene-d 5 in the same solvents. The order parameters of the non-deuterated solutes in the various solutions were calculated using the dipolar couplings of the proton spectra and the r* structures taken from the literature. The same order parameters were assumed to describe also the orientation of the deuterated solute in the corresponding solutions. Each 2H spectrum yielded three quadrupolar splittings for the three different deuterated positions in the labelled solute. The splittings from the three different solutions of the same solute, together with the order parameters and the rastructure, were used to determine DQCC and rjof the ortho, meta and para deuterons (Pyridine-ds: DQCCortho= 183(1) kHz, rionho = 0.030(5), DQCCmeta = 185(1) kHz, ^meta= o.030(10), DQCCPara= 188(6) kHz, ?/Para= 0.01(5). Benzonitrile-ds: DQCCortho= 171(12) kHz, >/ortho= 0.07(3), DQCCmeta= 175(12) kHz, nma*= 0.05(3), DQCCPara= 176(4) kHz, rjpara= 0.10(7). Chlorobenzene-d5: DQCCortho= 180(2) kHz, ^ortho= 0.06(1), DQCCmeta= 174(2) kHz, //meta = 0.09(3), DQCCPara= 182(4) kHz, //Para = 0.06(4)). The results are discussed, as well as the limits and possibilities of the method used. 
  Reference    Z. Naturforsch. 41a, 431 (1986) 
  Published    1986 
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 Identifier    ZNA-1986-41a-0431 
 Volume    41 
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