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2000[X]
1Author    J. G. Correia, J. P. Araújo, J. G. Marques, A. R. Ramos, A. A. Melo, J. C. SoaresRequires cookie*
 Title    Electron-Gamma PAC: New Possibilities for NQI Studies  
 Abstract    The application of hyperfine interaction techniques to problems in solid state physics has been stead-ily growing over the last decade with the use of radioactive ion beam facilities such as ISOLDE at CERN. New applications of the e~-y Perturbed Angular Correlation (PAC) technique are underway at ISOLDE using probe nuclei with highly converted cascades. In this paper we present the motivation for extend-ing PAC experiments to elements/isotopes not usable with the conventional y-y PAC technique. Examples will be shown where the long-lived 73 As/ 73 Ge, the short lived 127 Ba/ 127 Cs and the 197m Hg/ l97 Hg decay cascades are applied to measurements of nuclear quadrupole interactions in materials. 
  Reference    Z. Naturforsch. 55a, 3—14 (2000); received September 11 1999 
  Published    2000 
  Keywords    Nuclear Techniques, Hyperfine Fields, Semiconductors, Superconductors 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0003.pdf 
 Identifier    ZNA-2000-55a-0003 
 Volume    55 
2Author    H. J. JänschRequires cookie*
 Title    Study of Li Diffusion on Metal and Semiconductor Surfaces via NQI Presented at the XVth International Symposium on Nuclear Quadrupole Interactions  
  Reference    Z. Naturforsch. 55a, 15—20 (2000); received August 23 1999 
  Published    2000 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0015.pdf 
 Identifier    ZNA-2000-55a-0015 
 Volume    55 
3Author    Shuan Dong, Kazuhiko Yamada, Gang WuRequires cookie*
 Title    Oxygen-17 Nuclear Magnetic Resonance of Organic Solids  
 Abstract    We report solid-state l7 0 NMR determinations of the oxygen chemical shift (CS) and electric field gradient (EFG) tensors for a series of 17 0-enriched organic compounds containing various functional groups. In several cases, analysis of the n O magic-angle-spinning (MAS) and static NMR spectra yields both the magnitude and relative orientations of the 17 0 CS and EFG tensors. We also demonstrate the feasibility of solid-state 17 0 NMR as a potentially useful technique for studying molecular structure and hydrogen bonding. 
  Reference    Z. Naturforsch. 55a, 21—28 (2000); received September 11 1999 
  Published    2000 
  Keywords    Oxygen-17, Solid State NMR, Organic Compounds, Chemical Shift Tensor, Quadrupole Coupling Constant 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0021.pdf 
 Identifier    ZNA-2000-55a-0021 
 Volume    55 
4Author    Ming-Yuan Liao, Raju Subramanian, RachelL. Yung, GerardS. HarbisonRequires cookie*
 Title    Two and Three Dimensional Nuclear Quadrupole Resonance in the Investigation of Structure and Bonding  
 Abstract    A variety of two dimensional two-and three-dimensional NQR experiments are reviewed, showing their application to the determination of field gradients for important sites in peptides and proteins, for assigning connected transitions of nuclei with spin > 5/2, and for determining hexadecapolar coupling constants. The quadrupole coupling tensor for 63 Cu in the active site of a protein, bovine erythrocyte (Cu, Zn) superoxide dismutase, has been measured and is compared with the results of ab initio calculations. 
  Reference    Z. Naturforsch. 55a, 29—36 (2000); received August 26 1999 
  Published    2000 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0029.pdf 
 Identifier    ZNA-2000-55a-0029 
 Volume    55 
5Author    David Stephenson, JohnA S Smith, St Augustine, Tobago TrinidadRequires cookie*
 Title    Low Frequency NQR using Double Contact Cross-relaxation  
 Abstract    A cross-relaxation technique is described which involves two spin contacts per double reso-nance cycle. The result is an improvement in signal to noise ratio particularly at low frequencies. Experimental spectra and analyses are presented: 14 N in ammonium sulphate showing that the tech-nique gives essentially the same information as previous studies; 14 N in ammonium dichromate determining e 2 Qq/h as (76±3) kHz and r} = 0.84±.04; 7 Li in lithium acetylacetonate for which the spectrum (corrected for Zeeman distortion) yields e~Qq/h = (152 ±5) kHz and r\ -.5 ±.2. Calculated spectra are presented to demonstrate the r\ dependence of the line shapes for 7 Li. 
  Reference    Z. Naturforsch. 55a, 37—10 (2000); received September 11 1999 
  Published    2000 
  Keywords    NQR, l4 N, 7 Li, Low Frequency, Double Resonance 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0037.pdf 
 Identifier    ZNA-2000-55a-0037 
 Volume    55 
6Author    A. C. Junqueira, A. W. Carbonari, J.Mestnik Filho, R. N. SaxenaRequires cookie*
 Title    Electric Field Gradient at Nb Site in the Intermetallic Compounds Nb 3 X (X = AI, In, Si, Ge, Sn) Measured by PAC  
 Abstract    The electric field gradient (efg) at the Nb site in the intermetallic compounds Nb 3 X (X = Al, In, Si, Ge, Sn) was measured by the Perturbed Angular Correlation (PAC) method using the well-known gamma-gamma cascade of 133 -482 keV in lxl Ta from the ß~ decay of 1K1 Hf, substituting approximately 0.1 atom percent of Nb. The PAC results show that V zz drops by nearly 40% when X changes from Al to In, and by about 25% when X changes from Si to Ge and Sn. This behavior is most probably related to the change in the degree of sp hybridization in these compounds. The V zz values of the studied compounds do not follow the well known universal correlation for the efg's in non-cubic metals but the observed trend is well reproduced by results of ab-initio electronic structure calculations. In the case of Nb 3 Al a linear temperature dependence of the quadrupole frequencies was observed in the temperature range of 6.5 to 1210 K. 
  Reference    Z. Naturforsch. 55a, 41—14 (2000); received August 25 1999 
  Published    2000 
  Keywords    Electric Field Gradient, PAC Measurements, Nb-based Alloys, Quadrupole Interactions 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0041.pdf 
 Identifier    ZNA-2000-55a-0041 
 Volume    55 
7Author    K. Królas, M. Rams, J. WojtkowskaRequires cookie*
 Title    Quadrupole Interaction of 172 Yb and 168 Er Nuclei in the First Excited 2 + State  
 Abstract    We have measured the hyperfine interactions in YbVC>4 and YbPC>4 using 172 Yb perturbed angular correlation spectroscopy for 90 -1094 keV and 1094 -79 keV 7-7 cascades. The quadrupole interaction frequency varied with temperature from 0 to 2 GHz. Precise information was obtained from both cascades independently even using the cascade with the intermediate state of the half life as short as 1.6 ns. 
  Reference    Z. Naturforsch. 55a, 45—18 (2000); received September 11 1999 
  Published    2000 
  Keywords    Quadrupole Interaction, Perturbed Angular Correlations, 172 Yb, 16X Er, YbVCV 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0045.pdf 
 Identifier    ZNA-2000-55a-0045 
 Volume    55 
8Author    M. Marszałek, H. Saitovitch, P.R J SilvaRequires cookie*
 Title    Hyperfine Interactions at 181 Ta in Hf 2 Ni 7 and Zr 2 Ni 7  
  Reference    Z. Naturforsch. 55a, 49—53 (2000); received September 11 1999 
  Published    2000 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0049.pdf 
 Identifier    ZNA-2000-55a-0049 
 Volume    55 
9Author    G. B. Furman, S. D. Goren, A. M. Panich, A. I. ShamesRequires cookie*
 Title    Spin Diffusion in Pure Multiple-Pulse NQR  
 Abstract    We present a detailed theoretical and experimental NQR multiple-pulse spin-locking study of spin-lattice relaxation and spin diffusion processes in the presence of paramagnetic impurities in solids. The obtained diffusion equation was obtained allows to find the time dependence of the magnetization in the effective field. The spin lattice relaxation times were calculated, both for direct and diffusion regimes, as functions of the correlation time and multiple-pulse parameters. Measurements of relaxation times in rotating frame allow to determine the diffusion coefficient and the radius of the diffusion barrier in 7-irradiated polycrystalline samples of NaCIO}. 
  Reference    Z. Naturforsch. 55a, 54—60 (2000); received August 25 1999 
  Published    2000 
  Keywords    NQR, Paramagnetic Impurities, Spin Diffusion 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0054.pdf 
 Identifier    ZNA-2000-55a-0054 
 Volume    55 
10Author    J. L. Schiano, M. D. GinsbergRequires cookie*
 Title    A Pulsed Spectrometer Designed for Feedback NQR  
 Abstract    A pulsed NQR spectrometer specifically designed to facilitate real-time tuning of pulse sequence parameters is described. A modular approach based on the interconnection of several rack-mounted blocks provides easy access to all spectrometer signals and simplifies the task of modifying the spectrometer design. We also present experimental data that demonstrates the ability of the spectrometer to increase the signal to noise ratio of NQR measurements by automatically adjusting the pulse width in the strong off-resonant comb pulse sequence. 
  Reference    Z. Naturforsch. 55a, 61—66 (2000); received August 28 1999 
  Published    2000 
  Keywords    Nuclear Quadrupole Resonance, Spectrometer Design, Real-time Programmable Pulse Sequence Generator 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0061.pdf 
 Identifier    ZNA-2000-55a-0061 
 Volume    55 
11Author    J. L. Schiano, A. J. Blauch, M. D. GinsbergRequires cookie*
 Title    Optimization of NQR Pulse Parameters using Feedback Control  
 Abstract    A new method for increasing the probability of detecting nuclear resonance signals is demon-strated experimentally. It is well known that the detection of signals with a low signal to noise ratio (SNR) results in missed detections of false alarms. In situations where the noise is correlated or where limited data is averaging, it may not be possible to achieve a desired SNR through averaging alone. We present an alternative approach in which a feedback algorithm automatically adjusts pulse parameters so that the SNR and probability of correct detection are increased. Experimental results are presented for the detection of 14 N NQR signals. 
  Reference    Z. Naturforsch. 55a, 67—73 (2000); received August 28 1999 
  Published    2000 
  Keywords    Nuclear Quadrupole Resonance, Feedback Control, Receiver Operating Characteristics 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0067.pdf 
 Identifier    ZNA-2000-55a-0067 
 Volume    55 
12Author    M. Marszałek, Jerzy Grębosz, Jacek Jaworski, Zbigniew Stachura, Mirosław Ziębliński, Bernd Sulkio-ClefpRequires cookie*
 Title    The 8-Parameter List Mode for 7-7 Perturbed Angular Correlation Measurements  
 Abstract    A new TDPAC spectrometer which is based on the principle of event by event data acquisition (list mode) in order to reduce a background, avoid systematic errors and increase efficiency of the setup is described. The principal demand on the new spectrometer is the simultaneous measurement of all events containing the time and energy signals of the four detectors appearing in a preset common time window. For this purpose an 8-parameter list mode data acquisition system has been developed. 
  Reference    Z. Naturforsch. 55a, 74—78 (2000); received September 11 1999 
  Published    2000 
  Keywords    Time Differential Perturbed Angular Correlations (TDPAC), Spectrometers, List Mode, Event by Event, Data Acquisition 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0074.pdf 
 Identifier    ZNA-2000-55a-0074 
 Volume    55 
13Author    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 
14Author    Tetsuo Asaji, Tomohiro IshizakaRequires cookie*
 Title    Effect of Deuteration on Ammonium Motion and Structural Phase Transition Studied by Nuclear Quadrupole Resonance  
 Abstract    35 C1 NQR measurements revealed two phase transitions at 14.5 K and 70 K in NH4ICI4. By deuteration of the ammonium ions, the respective transition temperature increased to 27 K and 74 K. In the lowest-temperature phase of NH4ICI4, by the deuteration a remarkable change of the temperature dependence of the 35 C1 NQR frequencies was observed. The NQR spin-lattice relaxation-time minimum, ascribable to the modulation effect of the electric field gradient (EFG) due to a motion of the ammonium ions, was observed at 7 K and 11 K in NH4ICI4 and ND4ICI4, respectively. The activation energy of the ammonium motion and the fluctuation fraction q /q of the EFG were determined to be 0.32 kJ moP 1 and 1.3xlO~ 3 for NH4ICI4, and 0.30 kJ mol -1 and 0.88xl0~ 3 for ND4ICI4. The experimental result suggests that the inter-ionic interaction between the ammonium ion and the ICl^ complex anion is weakened by the deuteration. However, the frequency shift observed in the lowest-temperature phase is much larger in ND4ICI4 than in NH4ICI4. This suggests that the lattice distortion in NH4ICI4 is suppressed to a great deal by the tunneling rotation of NH4 ions. The effective inter-ionic interaction responsible for the lattice distortion, the transition temperature and the enhancement of tunneling of NH4 as compared with ND4 is discussed for NH4ICI4 as well as for previously reported NH4AUCI4 and ct-N^HgCb. 
  Reference    Z. Naturforsch. 55a, 83—89 (2000); received August 26 1999 
  Published    2000 
  Keywords    Isotope Effect, Tunneling, Phase Transition, Ammonium, NQR 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0083.pdf 
 Identifier    ZNA-2000-55a-0083 
 Volume    55 
15Author    Michael Uhrmacher, Klaus-Peter LiebRequires cookie*
 Title    Phase Transitions in Oxides Studied by Perturbed Angular Correlation Spectroscopy  
 Abstract    Radioactive atoms located on cation sites in oxide matrices can be used to monitor phase transitions by measuring the electric or magnetic hyperfine interactions by means of Perturbed Angular Correlations spectroscopy. The article illustrates three types of phase transitions studied with 11 'in tracers and their daughter nuclei m Cd, namely magnetic, structural and REDOX phase transitions in binary and ternary polycrystalline or single-crystalline oxides. In this context, we also discuss the question of identifying the probes' lattice site(s), the scaling of the Electric Field Gradients in oxides, the influence of the (impurity) probes themselves on the phase transitions, and the occurrence and mechanisms of dynamic interactions. Recent results on " 1 In in pure and Li-doped In 2 S 3 will also be presented. 
  Reference    Z. Naturforsch. 55a, 90—104 (2000); received August 26 1999 
  Published    2000 
  Keywords    Phase Transitions, Oxides, Perturbed Angular Correlations, 111 In, Point Charge Model 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0090.pdf 
 Identifier    ZNA-2000-55a-0090 
 Volume    55 
16Author    S. V. Verkhovskii, B. Z. Malkin, A. Trokiner, A. Yakubovskii, E. Hallet, A. Ananyev, A. Gerashenko, Yu Piskunov, S. Saikin, A. Tikhomirov, V. OzhoginRequires cookie*
 Title    Quadrupole Effects on 73 Ge NMR Spectra in Isotopically Controlled Ge Single Crystals  
 Abstract    NMR spectra of 73 Ge (nuclear spin / = 9/2) in perfect single crystals of germanium with different isotopic content were measured at 80, 300, and 450 K. The observed specific line shapes gave evidence of the isotopic disorder, in particular, abnormal broadening of the spectrum was found for the magnetic field directed along the [111] axis. Local lattice deformations in the germanium crystal lattice due to "isotopic disorder" were calculated in the framework of the adiabatic bond charge model. The results were applied to study random non-cubic crystal field interactions with the nuclear quadrupole moments and corresponding effects on NMR spectra. The simulated second moment of the resonance frequency distributions caused by the magnetic dipole-dipole and electric quadrupole interactions are used to analyze the lineshapes, theoretical predictions being in a qualitative agreement with the experimental data. 
  Reference    Z. Naturforsch. 55a, 105—110 (2000); received September 11 1999 
  Published    2000 
  Keywords    Isotopic Disorder, Ge Single Crystal, NMR Spectra, Quadrupole Effects 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0105.pdf 
 Identifier    ZNA-2000-55a-0105 
 Volume    55 
17Author    K. P. Ramesh, J. Ramakrishna, K. S. Suresh, C.Raghavendra RaoRequires cookie*
 Title    Pressure Dependence of the Chlorine NQR in Chloro Pyridines  
 Abstract    The "CI NQR frequency (VQ) and spin lattice relaxation time) in 2,6-dichloropyridine, 2 amino 3,5-dichloropyridine and 6 chloro 2-pyridinol have been measured as a function of pressure up to 5.1 kbar at 300 K, and the data have been analysed to estimate the temperature coefficients of the NQR frequency at constant volume. All the three compounds show a non linear variation of the NQR frequen-cy with pressure which can be described by a 2 nd order polynomial in pressure. The rate of change of the NQR frequency with pressure is positive and decreases with increasing pressure. The spin lattice re-laxation time 7, in all the three compounds shows a small increase with pressure, indicating that the re-laxation is mainly due to the torsional motions. 
  Reference    Z. Naturforsch. 55a, 111—116 (2000); received August 25 1999 
  Published    2000 
  Keywords    Chlorine NQR, Spin-Lattice Relaxation Time, Pressure Dependence, 2,6 dichloropyridine, 2-amino 3,5-dichloropyrine, 6-chloro 2-pyridinol 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0111.pdf 
 Identifier    ZNA-2000-55a-0111 
 Volume    55 
18Author    Yasumasa Tomita, Hiroshi Ohki, Koji Yamada, Tsutomu OkudaRequires cookie*
 Title    Dynamic Behavior of Group 13 Elements in Bromocomplexes as Studied by NQR and NMR  
 Abstract    NMR, NQR, powder X-ray diffraction, DTA and AC conductivity were measured in RMBr 4 (R = Ag, Cu; M = Al, Ga) and RMiBr 7 (R = Li, Ag; M = Al, Ga). In RMBr 4 , the activation energy of Cu + diffusion was evaluated from ^Cu NMR and was in good agreement with that from S1 Br NQR. In CuAlBr 4 , the e 2 Qq/h value of 63 Cu NMR and the 77 value of 27 AI NMR changed linearly with decreasing temperature, although the e 2 Qq/h value of 27 AI NMR did not change so much. These temperature dependences are supposed to be due to Cu + diffusion and not to a variation of the lattice constants. In RMiBr 7 , the activation energy was obtained from the spin-lattice relaxation time T x of 81 Br NQR and is ascribed to a modulation of the cation diffusion. The line width of 7 Li NMR in LiAl 2 Br 7 was about 5.9 kHz in the low-temperature phase and 0.4 kHz for the high-temperature phase. The 27 A1 NMR spectrum was broadened by the quadrupole interaction and unchanged up to 400 K, suggesting that diffusion of Li + ions occurs in the high-temperature phase. 
  Reference    Z. Naturforsch. 55a, 117—123 (2000); received August 25 1999 
  Published    2000 
  Keywords    T x of 81 Br NQR, 27 A1 NMR, 7 Li NMR, 63 Cu NMR, Cation Diffusion 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0117.pdf 
 Identifier    ZNA-2000-55a-0117 
 Volume    55 
19Author    Ho Choh, JaeKap JungRequires cookie*
 Title    Sung  
 Abstract    External influences on the 14 N NQR of ferroelectric NaN0 2 , such as changes of the temperature, electric field, stress, gamma-ray irradiation, and impurity doping are reviewed. They normally cause either a frequency shift or a broadening of the 14 N NQR lines and are strongly related to the change of the spontaneous polarization. 
  Reference    Z. Naturforsch. 55a, 124—128 (2000); received August 23 1999 
  Published    2000 
  Keywords    l4 N NQR, Ferroelectric NaN0 2, Spontaneous Polarization, External Effects, Impurity 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0124.pdf 
 Identifier    ZNA-2000-55a-0124 
 Volume    55 
20Author    GaryS. Collins, LukeS., -J Peng, MatthewO. ZacateRequires cookie*
 Title    Search for Nucleation of Phase Embryos in Binary Alloys by Impurity Atoms  
  Reference    Z. Naturforsch. 55a, 129—133 (2000); received August 25 1999 
  Published    2000 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0129.pdf 
 Identifier    ZNA-2000-55a-0129 
 Volume    55 
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