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1994 (206)
1Author    C. LarkeRequires cookie*
 Title    Low Frequency Nuclear Quadrupole Resonance with SQUID Amplifiers  
 Abstract    The dc S Q U ID (Superconducting Q Uantum Interference Device) can be configured as an am pli­ fier o f spin-echos with a noise temperature of approximately 10 mK (f/1 M Hz) at an operating temperature of 1.5 K. A Fourier transform spectrometer based on a S Q U ID with a superconducting input circuit and operated in a flux-locked loop is used to obtain nuclear quadrupole resonance (N Q R) spectra in a broadband m ode over the bandwith 0 -1 M Hz. Spin-echo spectra of 14N in N H 4C 104 reveal sharp N Q R resonances, obtained simultaneously, at 17.4, 38.8 and 56.2 kHz. At 1.5 K, the measured longitudinal and transverse relaxation times Tx and T2 for the 38.8 kH z transi­ tion are 63 ± 3 ms and 22 + 2 ms, respectively. 
  Reference    Z. Naturforsch. 49a, 5 (1994); received O ctober 18 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0005.pdf 
 Identifier    ZNA-1994-49a-0005 
 Volume    49 
2Author    TiloB. Lasberg, D.Ieter SuterRequires cookie*
 Title    Determination of the Sign of Nuclear Quadrupole Interaction by Laser-Radiofrequency Double-Resonance  
 Abstract    We describe a new type of laser-radiofrequency double-resonance experiment, which allows to determine not only the absolute value but also the sign of nuclear quadrupole coupling constants. This determination of the sign, which is essential for the comparison with calculated EFG tensors, is not possible with purely magnetic experiments. The m ethod has a high resolution and, because of the optical detection, also a high sensitivity. As an example, the quadrupole coupling constant for Pr3 + :YA103 was measured at 4.38 K and was found to be negative. 
  Reference    Z. Naturforsch. 49a, 14—1 (1994); received August 8 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0014.pdf 
 Identifier    ZNA-1994-49a-0014 
 Volume    49 
3Author    B. BliimichRequires cookie*
 Title    Wideline 2H -NM R Spectroscopy and Imaging of Solids  
 Abstract    Recent developm ents, focussing on reduction of the rf excitation power by stochastic excitation, on im provements in sensitivity and excitation bandwidth by magic angle spinning, and on com ­ bining wideline spectroscopy with spatial resolution for investigations o f spatially inhom ogeneous objects are reviewed. 
  Reference    Z. Naturforsch. 49a, 19—2 (1994); received August 5 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0019.pdf 
 Identifier    ZNA-1994-49a-0019 
 Volume    49 
4Author    C.Requires cookie*
 Title    ^-Radiation Detected NMR in Solid and Liquid Neon  
 Abstract    Spin-polarized ^-active 23N e (Tx,2 = 37.2s) nuclei were created by capture of polarized cold neutrons in solid and liquid neon. The angular asymmetry of the ^-radiation was used to m onitor the nuclear polarization. From nuclear m agnetic resonance curves the value for the dipole m om ent |/x(23Ne)| = 1.079(1) n.m. (uncorrected) was obtained which is more precise than the literature value. Com paring the measured spin-lattice relaxation rates with those of stable 21N e the nuclear quadru­ pole m om ent of 23N e was determined. It agrees with a shell model calculation. The feasibility of 23Ne-/?-NM R for investigations in condensed rare gases in demonstrated. Key words: /5-radiation detected N M R , Solid and liquid N eon, / i(23N e), ß (23N e), Nuclear spin relaxation. 
  Reference    Z. Naturforsch. 49a, 27 (1994); received July 23 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0027.pdf 
 Identifier    ZNA-1994-49a-0027 
 Volume    49 
5Author    J. Seliger, V. Ž. Agar, R. BlincRequires cookie*
 Title    H -14N Nuclear Quadrupole Double Resonance with Multiple Frequency Sweeps  
 Abstract    A new highly sensitive XH -14N nuclear quadrupole double resonance technique is presented which is based on magnetic field cycling and on the application of multiple frequency sweeps of an r.f. magnetic field. The sensitivity and the resolution o f the new technique are estimated. Some experimental results obtained by the new technique are presented. Key words: 14N nuclear quadrupole resonance; D ouble resonance; M agnetic field cycling; A dia­ batic fast passage. 
  Reference    Z. Naturforsch. 49a, 31 (1994); received July 3 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0031.pdf 
 Identifier    ZNA-1994-49a-0031 
 Volume    49 
6Author    H. Robert, D. PusiolRequires cookie*
 Title    On the Reconstruction of NQR Nutation Spectra in Solids with Powder Geometry  
 Abstract    In single crystals the NQ R nutation frequency depends on the relative orientation of the coil and the quadrupole axes. In powders the nutation lineshape is a superposition of spectra from the randomly oriented single crystals, so that powder patterns appear in such experiments if the recon­ struction is performed by the Fourier transform method. In this paper an alternative reconstruction method of nutation spectra is suggested making use of the Hankel Transform. In this way the nutation spectra are simplified. Singularities arising with experiments for the determination of the asymmetry parameter rj can easily be resolved. In the particular case of an axially symmetric quadrupolar tensor and a hom ogeneous radiofrequency field one can reduce the powder pattern to a single line w ithout heterogeneous broadening with respect to orientation. Further improvement o f the nutation spectra can be achieved by taking advantage of the maximum entropy method, which strongly reduces apodisation and noise problems. Applications of the new data m anipulation techniques to N Q R imaging m ethods published elsewhere and 2D zero-field N Q R spectroscopy are reported. 
  Reference    Z. Naturforsch. 49a, 35—4 (1994); received August 14 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0035.pdf 
 Identifier    ZNA-1994-49a-0035 
 Volume    49 
7Author    M. Ariusz, M. Aćkow Iak, M. Arek BojarskiRequires cookie*
 Title    Automatically Tuned Probe Head System for Pulsed NQR Spectroscopy in Extreme Thermodynamic Conditions * M ich ał O stafin  
 Abstract    A com plete N Q R probe-head system operating in the frequency ranges 0 .5 -1 5 0 and 150— 300 M H z is described. The head is particularly suited for N Q R experiments carried out at a remote location, for example in a low-temperature cryostat or high-pressure chamber. M oreover, the head system includes a microprocessor-controller for automated tuning of the probe to the operating frequency of the associated N Q R spectrometer. The controller can be easily interfaced to a PC via standard serial port. 
  Reference    Z. Naturforsch. 49a, 42 (1994); received July 23 1993 
  Published    1994 
  Keywords    Nuclear quadrupole resonance, Pulsed spectrometers, Instrum entation 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0042.pdf 
 Identifier    ZNA-1994-49a-0042 
 Volume    49 
8Author    O. Tte R, K. K., Ze Lm, G. M., Je Rb, A. SeegeraRequires cookie*
 Title    Investigation of Intrinsic Point Defects in Metals by Nuclear Quadrupole Double Resonance  
 Abstract    The paper reviews the principal features of the Nuclear Q uadrupole D ouble Resonance (N Q D O R) technique, with particular emphasis on its application to the investigation o f imperfec­ tions in cubic metals. N Q D O R permits measurements o f the electric field gradients (EFG) at quadrupole-m oment-carrying nuclei in the neighbourhood of point defects and thus to obtain "fingerprints" of these defects. An N Q D O R facility set-up at the M ax-Planck-Institut für M etall­ forschung in Stuttgart is described. It has been used to study the intrinsic defects introduced into Cu and dilute Cu/Be alloys by low-temperature irradiation with electrons or protons or by cold-work. It is shown that all well-resolved irradiation-induced EFG observed in the present work are due to one kind o f defect only, which is identified as the <100) dumbbell self-interstitial. When considered together with measurements of the electrical resistivity on the same specimens, the annealing be­ haviour of the N Q D O R lines supports the so-called two-interstitial model o f radiation damage in face-centred cubic metals rather than the one-interstitial model. 
  Reference    Z. Naturforsch. 49a, 47 (1994); received October 26 1993 
  Published    1994 
  Keywords    Nuclear quadrupole double resonance, Self-interstitials, Vacancies, Radiation dam ­ age, Intrinsic point defects in copper 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0047.pdf 
 Identifier    ZNA-1994-49a-0047 
 Volume    49 
9Author    G. L. Petersen, P. J. Bray, R.A M ArinoRequires cookie*
 Title    A New Pulsed Nuclear Quadrupole Resonance Spectrometer  
 Abstract    A new pulsed nuclear quadrupole resonance spectrometer is described and a number of Nitrogen-14 spectra are shown and discussed. The spectrometer is computer interfaced and both data acqui­ sition and all adjustments other than the matching network tuning are automatic. Spectra may be produced using fast Fourier transforms or by the Clark Method. The latter is particularly valuable when very wide line widths are encountered. 
  Reference    Z. Naturforsch. 49a, 65—7 (1994); received November 18 1993 
  Published    1994 
  Keywords    Nuclear quadrupole resonance, Spectrometer, Instrumentation, Fourier transform 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0065.pdf 
 Identifier    ZNA-1994-49a-0065 
 Volume    49 
10Author    B. C. Sanctuary, M. Angala, S. K. Rish, N. AnRequires cookie*
 Title    Theory of NQR Pulses  
 Abstract    Pulses applied to spin systems with I > 1/2 in the absence of any external fields, the NQR case, are fundamentally different from NMR pulses. In particular, both rotating and counter-rotating components of the rf field must be kept in NQR, whereas only the "in phase" component need be retained in NMR. NQR pulses are illustrated for 7 = 3 / 2 in an axially symmetric electric field gradient (EFG). 
  Reference    Z. Naturforsch. 49a, 71—7 (1994); received October 27 1993 
  Published    1994 
  Keywords    NQR, Pulse, Density matrix, NMR 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0071.pdf 
 Identifier    ZNA-1994-49a-0071 
 Volume    49 
11Author    M. Baldus, T. O. Levante, B.H M EierRequires cookie*
 Title    Numerical Simulation of Magnetic Resonance Experiments: Concepts and Applications to Static, Rotating and Double Rotating Experiments  
 Abstract    An object-oriented programming environment for numerical simulation of magnetic resonance spectra is introduced and applied to NQR and NMR of quadrupolar nuclei. Using a Floquet approach it is possible to perform simulations of spin systems that are described by explicitly time-dependent Hamiltonians in full analogy to simulations of time-independent systems. Applica­ tions to magic angle spinning and double rotation are discussed. 
  Reference    Z. Naturforsch. 49a, 80—8 (1994); received August 31 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0080.pdf 
 Identifier    ZNA-1994-49a-0080 
 Volume    49 
12Author    PascalP M AnRequires cookie*
 Title    Solomon Echoes Extended to Soft Pulse Excitation  
 Abstract    Solomon echoes, produced by two in-phase pulses separated by a delay r2, are derived in taking into account the first-order quadrupolar interaction during the pulses. Consequently, the results are valid for any ratio of the quadrupolar coupling, coQ, to the amplitude of the radiofrequency pulse, <yRF. Six echoes are predicted after the second pulse: three, detected as inner satellite signals, occur at t 4 = r2, t 4 = 2 t 2 and t 4 = 3 1 2; the other three, detected as outer satellite signals, occur at t 4 = r 2 /2, t 4 = t 2 , and t4 = 3 t 2 /2. These echoes originate from the refocusing of single-and multi-quantum off-resonance coherences developed during the first pulse. Four of them are allowed echoes, the other two are forbidden ones. However, there is no echo for the central transition. From a practical point of view this means that r2 must be short compared to TFID, the duration of the FID of the central transition. The behavior of the echo amplitude versus the second pulse length is discussed for several ratios of coQ/coRF. 
  Reference    Z. Naturforsch. 49a, 89 (1994); received July 23 1993 
  Published    1994 
  Keywords    Quadrupole effect, Spin-5/2, Spin echo NM R, Solomon echoes 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0089.pdf 
 Identifier    ZNA-1994-49a-0089 
 Volume    49 
13Author    U. RmRequires cookie*
 Title    Nitrogen-14 NQR Multiple-Pulse Spin-locking in the Axial Electric Field Gradient  
 Abstract    The behavior of a nuclear spin-1 system with the Hamiltonian including: a) the interaction of the electric quadrupole moment of nuclei with the axial gradient of the crystal electric field; b) a homonuclear and heteronuclear dipole-dipole coupling; and c) the interaction with a multiple pulse radiofrequency field of arbitrary orientation was considered. The effective Hamiltonian is con­ structed by using the Floquet theory. The secular parts of the homonuclear and heteronuclear dipole-dipole interaction was found and the quasi-equilibrium magnetization was calculated. 
  Reference    Z. Naturforsch. 49a, 97 (1994); received September 4 1993 
  Published    1994 
  Keywords    NQR, Multiple-pulse spin-locking, Nitrogen-14 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0097.pdf 
 Identifier    ZNA-1994-49a-0097 
 Volume    49 
14Author    H. Anspeter, H. UberRequires cookie*
 Title    Calculation of Quadrupole Coupling Constants: From Gas to Liquid  
 Abstract    Nuclear quadrupole coupling constants for D, 14N and 170 calculated with basis sets of high local quality are reviewed. It is confirmed that the concept of high local quality gives reliable results for many molecules in the gas phase. The calculations are extended to the condensed phase by combining quantum chemical calculations with molecular dynamics simulations. An excellent agree­ ment with experiment is obtained for the deuterium coupling in liquid D 20 and a fair agreement for 170 coupling in liquid H 2170 . The 21N e nmr relaxation time in liquid neon is calculated to be within about 20% of experimental values, an exact comparison being difficult due to only roughly known pressures in the experiment and not adequately treated quantum effects in the simulations. Comparisons in the dense supercritical region at higher temperatures would be of interest, but experimental data are lacking. 
  Reference    Z. Naturforsch. 49a, 103—115 (1994); received July 23 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0103.pdf 
 Identifier    ZNA-1994-49a-0103 
 Volume    49 
15Author    G. Erald Frantz, Hagen Dufner, P. C. SchmidtRequires cookie*
 Title    Theoretical Investigation on the Nuclear Quadrupole Interaction of CH3CI, CH2C12 and CHC13  
 Abstract    The nuclear quadrupole interaction of 3 5 C1 in C H 3 C1, C H 2 C12 and CHC13 has been studied theoretically by the H artree-Fock-R oothaan procedure. The influence of the crystal field on the nuclear quadrupole coupling constant is incorporated by the cluster approach and by using point charges that are consistent with the external potential. 
  Reference    Z. Naturforsch. 49a, 116—124 (1994); received November 11 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0116.pdf 
 Identifier    ZNA-1994-49a-0116 
 Volume    49 
16Author    P. W. Fowler, H. M. KellyRequires cookie*
 Title    Sternheimer Factors and Electric-Field-Gradient Hyperpolarisabilities for Ions in Crystals  
 Abstract    Analytic coupled Hartree-Fock calculations of the electric field gradient response properties y (the Sternheimer shielding factor) and e (the dipole-dipole-electric field gradient hyperpolarisability) have been carried out on anions in clusters that simulate that crystal environment. The systems studied are F _ in LiF and NaF, C l-in LiCl and NaCl, O 2-in MgO, S2_ in MgS, and H~ in LiH. Both properties show large reductions from free-ion values and significant variation with lattice param ­ eter, and the results indicate that damped values of anion Sternheimer factors will be necessary in accurate simulation of N Q R data or modelling of properties of ion-pairs. 
  Reference    Z. Naturforsch. 49a, 125—128 (1994); received 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0125.pdf 
 Identifier    ZNA-1994-49a-0125 
 Volume    49 
17Author    P. Blaha, K. Schwarz, P. Dufek, G. Vielsack, W. WeberRequires cookie*
 Title    The Breathing Mode of B a B i0 3: Electric Field Gradient and Total Energy Calculations  
 Abstract    We present ab initio full-potential linearized augmented plane wave (LAPW) band structure calculations for BaBiOa. We focus on total energies and electric field gradients at the oxygen site and present results for the breathing mode in the experimentally observed cubic and monoclinic struc­ tures of doped and undoped Baj _JC K xB i0 3. 
  Reference    Z. Naturforsch. 49a, 129—132 (1994); received 
  Published    1994 
  Keywords    B aB i03, Total energy, Electric field gradient, Energy band structure, Breathing mode 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0129.pdf 
 Identifier    ZNA-1994-49a-0129 
 Volume    49 
18Author    E.A C LuckenRequires cookie*
 Title    A Theoretical Study of the Vibrational Dependence of the Nuclear Quadrupole Coupling Constants of some Diatomic Molecules  
 Abstract    The nuclear quadrupole coupling constant was calculated as a function of inter nuclear distance for nine quadrupolar nuclei in eight diatom ic molecules by the STO 321G method. From the value of the field-gradient and its first and second derivatives the vibrational dependence of the coupling constants were calculated and shown to com pare satisfactorily with experiment. The behaviour of the field-gradient as a function of inter nuclear distance can in most cases be rationalized in terms of the field-gradient that will arise for the infinitely separated atoms. 
  Reference    Z. Naturforsch. 49a, 133—136 (1994); received August 23 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0133.pdf 
 Identifier    ZNA-1994-49a-0133 
 Volume    49 
19Author    MichaelH P Alm Er1, JohnA B Lair-Fish2Requires cookie*
 Title    Quadrupole Coupling Assignments in Inorganic Periodic Systems by ab initio Calculation of Electric Field Gradients  
 Abstract    Ab initio SCF calculations were performed in the unit cell environment, making use of the periodic behaviour to compute a wave-function for the bulk material. Electric field gradient (EFG) calcula­ tions were performed on the resulting wave-functions, and these are compared with experimental quadrupole coupling parameters. Examples of inorganic molecular and ionic crystals (nitrogen, chlorine and lithium nitride) and minerals or partially covalent lattice structures (alumina, petalite, a-quartz, boron oxide, boron nitride and sulphur nitride) are described. The effects of the basis set in these calculations are considered, and the limitations imposed by the nature of the calculation are described. 
  Reference    Z. Naturforsch. 49a, 137—145 (1994); received July 23 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0137.pdf 
 Identifier    ZNA-1994-49a-0137 
 Volume    49 
20Author    MichaelH P Alm Er3, JohnA B Lair-FishbRequires cookie*
 Title    Quadrupole Coupling in some H-bonded Organic Systems by ab initio Lattice Calculations of Electric Field Gradients  
 Abstract    We present ab initio H artree-Fock lattice calculations performed in the unit cell environment, to compute a wave-function and the derived electric field gradients for the bulk material. These calculations differ from cluster calculations by including the effects of more distant neighbour molecules. Examples considered are ammonia, formamide, oxamide, urea, thiourea, uracil, para-banic acid, alloxan, guanidine bicarbonate and melamine. 
  Reference    Z. Naturforsch. 49a, 146—154 (1994); received November 8 1993 
  Published    1994 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-0146.pdf 
 Identifier    ZNA-1994-49a-0146 
 Volume    49 
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