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1992[X]
61Author    Rainer Kimmich, Eberhard Rommel, Peter Nickel, Daniel PusiolRequires cookie*
 Title    NQR Imaging  
 Abstract    A rotating-frame NQR imaging (ßNQRI) procedure based on pure NQR is reported. The tech-nique is suitable for powdery or crystalline solid materials containing quadrupole nuclei. The spatial information is encoded by gradients of the radio frequency amplitude of the excitation pulse. A special deconvolution procedure has been developed for the analysis of the spatial information encoded in the pseudo-FID of the NQR signal in the case of powder geometry. The technique is applicable to rotationally symmetric as well as to asymmetric electric field gradient tensors. The RF gradients are suitably produced by surface coils. The prominent advantage of surface-coil NQR is that objects larger than the coil diameter can be investigated. The imaging procedure then provides depth resolution in a range of the order of the coil radius. The technique is particularly suitable for the detection of gradients of physical parameters influencing the NQR line shift and of spatial distributions of the chemical composition. Examples are stress or temperature gradients. Two-dimensional images have been produced by rotating the sample step by step. For each orientation a profile across the sample is evaluated as the projection on the direction of the radio-frequency gradient. A projection-reconstruction formalism then permits the rendering of two-dimensional NQR images. 
  Reference    Z. Naturforsch. 47a, 361—366 (1992); received June 8 1991 
  Published    1992 
  Keywords    NQR, Imaging, Rotating-frame zeugmatography, Surface coil, Backprojection, Decon-volution 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0361.pdf 
 Identifier    ZNA-1992-47a-0361 
 Volume    47 
62Author    A. C. Legon, P. W. FowlerRequires cookie*
 Title    Weak Complexes of Dinitrogen: An Approach to the 14 N-Nuclear Quadrupole Coupling Constant of Free N 2  
 Abstract    The 14 N-nuclear quadrupole coupling constants z afl (14 N<2>) and x aa (14 N (1)) for the ground-states of the dimers 14 N (2) ' N (1| • • • HCCH and 14 N (2) 14 N (1) • • • HC 15 N have been corrected for zero-point effects and for the electrical effects of the subunit HX to give two estimates /(14 N) = —5.01 (13) and — 5.07 (8) MHz, respectively, for the coupling constant of the isolated 14 N 2 molecule. 
  Reference    Z. Naturforsch. 47a, 367—370 (1992); received August 27 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0367.pdf 
 Identifier    ZNA-1992-47a-0367 
 Volume    47 
63Author    S.F J CoxRequires cookie*
 Title    Detection of Quadrupole Interactions by Muon Level Crossing Resonance  
 Abstract    The positive muon proves to be a very versatile and sensitive magnetic resonance probe: im-planted in virtually any material its polarisation may be monitored via the asymmetry in its radioactive decay, giving information on the sites occupied by the muon in lattices or molecules, and the local fields experienced at these sites. The scope of these experiments has been greatly extended by the development of a technique of cross relaxation or level crossing resonance which allows quadrupole splittings on nuclei adjacent to the muon to be measured. The principles of the tech-nique and the conditions necessary for detection of the spectra are described, together with a number of applications. Of especial interest is the manner in which muons mimic the behaviour of protons in matter. In metal lattices, for instance, muons invariably adopt the same interstitial sites as do protons in the dilute hydride phases, so that they can be used to study problems of localisation and diffusion common to those of hydrogen in metals. Studies of the muon level crossing resonance in copper have given valuable information on the crystallographic site, electronic structure and low temperature mobility of the interstitial defect. In semiconductors, muons are expected to trap at other impurities -notably acceptors -in processes analogous to the passivation of dopants by hydrogen. Muon resonance offers the exciting prospect of spectroscopic study of these passivation complexes. In molecular materials, substitution of protons by muons can be thought of rather like deuteration. Muons implanted in ice produce a significant change in the quadrupole coupling constant of adjacent 17 Ö nuclei which may be traced to the effects of the large muon zero point energy; the resonance spectrum also exhibits temperature dependent features which may be informa-tive on the nature and lifetime of defects in the ice structure. Muon level crossing resonance has already been studied in an oxide superconductor and this relatively young field is now wide open for quadrupole interaction studies in other materials, using a variety of nuclei. 
  Reference    Z. Naturforsch. 47a, 371—381 (1992); received September 16 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0371.pdf 
 Identifier    ZNA-1992-47a-0371 
 Volume    47 
64Author    E. Rommel, P. Nickel, F. Rohmer, R. Kimmich, C. Gonzales, D. PusiolRequires cookie*
 Title    Two-dimensional Exchange Spectroscopy Using Pure NQR  
 Abstract    Exchange between positions with different resonance frequencies can be studied by two-dimen-sional spectroscopy originally developed for the NMR case. Cross intensity reflects changes of the resonance frequency due to different line shifts or anisotropic interactions. We now present analogous experiments carried out with pure NQR of polycrystalline samples. The specific require-ments are discussed in comparison to 2D exchange NMR spectroscopy. The method has been demonstrated with chloroform and p-chlorobenzotrichloride, where the resonances of the 35 C1 nuclei were investigated. Isomeric changes taking place in these compounds reveal themselves as cross-peaks provided the right ranges of the temperature and the mixing time are chosen. The corresponding dependences were recorded and are discussed. 
  Reference    Z. Naturforsch. 47a, 382—388 (1992); received August 1 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0382.pdf 
 Identifier    ZNA-1992-47a-0382 
 Volume    47 
65Author    H.-R Blank, M. Frank, J. Heindl, M. Kaltenhäuser, H. Köchner, W. Kreische, N. Müller, S. Porscher, T. WagnerRequires cookie*
 Title    A Simple Model to Explain 19 F-TDPAD Amplitude Characteristics  
 Abstract    Since many years the 19 F-TDPAD method (TDPAD = time differential perturbed angular distri-bution) has been used to investigate electric field gradients in fluorine compounds. In these experi-ments always a strong reduction of the observed interaction amplitudes is observed. To explain these characteristics, a simple kinematic model is suggested. 
  Reference    Z. Naturforsch. 47a, 389—394 (1992); received July 29 1991 
  Published    1992 
  Keywords    TDPAD, Quadrupole interaction, Fluorine, Perturbation amplitude, Temperature dependence 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0389.pdf 
 Identifier    ZNA-1992-47a-0389 
 Volume    47 
66Author    Feng Zhenye, EdwinA C Lücken, Jacques DiolotRequires cookie*
 Title    A Computer-controlled, Fully Automatic NMR/NQR Double Resonance Spectrometer  
 Abstract    A completely automatic computer-controlled NMR/NQR double resonance spectrometer is described. It features automatic tuning of the low, variable frequency power amplifier, thus permit-ting untended use over long periods, with high sensitivity and signal reproducibility. The sample is transferred between the low-frequency, zero-field region and the high-field region using compressed air and the possibility of switching on a field of several tens of gauss during the transfer of the sample is also included. 
  Reference    Z. Naturforsch. 47a, 395—400 (1992); received July 27 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0395.pdf 
 Identifier    ZNA-1992-47a-0395 
 Volume    47 
67Author    Osamu Ege, Sanyo Hamai, Hisao NegitaRequires cookie*
 Title    Zeeman NQR Studies on Polycrystals of Copper Compounds, Arsenic Compounds, and Chlorine Compounds  
 Abstract    Powder Zeeman NQR (PZNQR) spectra of 63 Cu, 75 As, and 35 C1 in various compounds have been observed at 77 K. On the basis of the types of simulated integral curves of PZNQR absorption, the estimated asymmetry parameters of the electric field gradients have been divided into three classes; (1) measurable, (2) small (smaller than about 0.05), and (3) very small (probably zero). The asymmetry parameters have been found to be very small (Cu, NQR frequency = 26.704 MHz) in Cu,0; 0.40 (63 Cu, 32.617 MHz) in KCu(CN) 2 ; very small (75 As, 116.820 MHz) in As 2 0 3 ; very small (75 As, 78.950; 35 C1, 25.0567 and 25.4036 MHz) and small (35 C1, 24.9581 MHz) in ASC13; very small (75 As, 98.501 and 99.046 MHz) in As(C 6 H 5) 3 ; small (38.389 MHz), 0.15 (38.464 MHz), and 0.14 (38.503 MHz) for 35 C1 in hexachlorobenzene; small (35.847 MHz) and very small (39.154, 39.603, and 39.615 MHz) for 35 C1 in l-chloro-2-(trichloromethyl)-benzene; small (32.619 MHz) and very small (32.878 MHz) for 35 C1 in 1,4-dichlorobutane; very small (37.828 and 38.051 MHz) for 35 C1 in 1,1,1 -trichloroethane. 
  Reference    Z. Naturforsch. 47a, 401—408 (1992); received July 26 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0401.pdf 
 Identifier    ZNA-1992-47a-0401 
 Volume    47 
68Author    G. B. Furman, I. M. Kadzhaya, G. E. Kibrik, A. Yu, I. G. Poljakov, ShaposhnikovRequires cookie*
 Title    NQR Spin Echo in the Effective Fields of Multiple-Pulse Sequences  
 Abstract    Results of a study, both theoretical and experimental, of a new kind of NQR spin echo technique are reported and discussed. 
  Reference    Z. Naturforsch. 47a, 409—411 (1992); received November 21 1991 
  Published    1992 
  Keywords    NQR, Spin echo, Multiple-pulse sequence 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0409.pdf 
 Identifier    ZNA-1992-47a-0409 
 Volume    47 
69Author    G. B. Furman, I. M. KadzhayaRequires cookie*
 Title    Zeeman Effect of Pure NQR in a Rotating Frame (CW and Pulsed Excitation)  
 Abstract    The Zeeman effect in a rotating frame is considered for the case when the quadrupolar nuclear spin system is acted on by two radio-frequency fields. 
  Reference    Z. Naturforsch. 47a, 412—414 (1992); received November 21 1991 
  Published    1992 
  Keywords    NQR, Zeeman effect, Radio-frequency field Rotating frame 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0412.pdf 
 Identifier    ZNA-1992-47a-0412 
 Volume    47 
70Author    S. S. Kim, J.R P Jayakody, R. A. MarinoRequires cookie*
 Title    Experimental Investigations of the Strong Off-Resonant Comb (SORC) Pulse Sequence in 14 N NQR  
 Abstract    The behavior of induction signals during steady-state pulse irradiations in 14 N NQR was inves-tigated experimentally. It has long been known that the signal response to a long sequence of rf pulses will dramatically increase for pulse spacings less than T 2 . This increase is exponential, and can result in signals comparable to optimally prepared Free Induction Decays. Because these "SORC" signals recur as long as the pulsing continues, very efficient signal-averaging can result. The dependence of these quasi steady-state signals on pulse parameters and on frequency offset are presented, together with a discussion of the applicability of the method. 
  Reference    Z. Naturforsch. 47a, 415 (1992); received December 11 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0415.pdf 
 Identifier    ZNA-1992-47a-0415 
 Volume    47 
71Author    Roberto Ambrosetti, Claudia Forte, Domenico RicciRequires cookie*
 Title    N Fourier Transform Nuclear Quadrupole Resonance. Instrumentation: Measurements on Cyanuric Chloride  
 Abstract    A Matec pulsed instrument, already equipped with a laboratory-built data system, has been considerably improved by adding new capabilities, such as versatile pulse sequence programming. Among other things, this allows automated Tx relaxation measurements. The instrument has been employed to record the 14 N NQR FT spectrum of cyanuric chloride and measure its Ti relaxation time from 77 K to the melting point at 418 K. The four-line 14 N spectrum indicates the presence of two chemically inequivalent sites. The intensity ratio of the lines identifies the site pertaining to a couple of symmetry-related 14 N nuclei. The lines smoothly decrease in frequency up to the melting point, where they remain narrow and almost equally spaced. Considering previous results at 4.2 K, this indicates that a single phase is stable over the entire accessible temperature range. The relaxation time Tj decreases smoothly with increasing temperature, with a T~ 2 law, from nearly 180 s at 77 K to about 1 s near the melting point, where a precipitous decrease starts. The high Ti values found are consistent with the lack of nuclei having high magnetic moment. 
  Reference    Z. Naturforsch. 47a, 421—429 (1992); received August 23 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0421.pdf 
 Identifier    ZNA-1992-47a-0421 
 Volume    47 
72Author    V. S. Grechishkin, N. Ja, SinjavskyRequires cookie*
 Title    Two-dimensional Two-frequency NQR Spectroscopy  
 Abstract    Two-dimensional NQR spectroscopy is experimentally accomplished by direct detection; for-bidden transitions are also recorded. Two-dimensional spectra with cross-peaks are used in assigning lines in complex spectra. A method is described of increasing the 14 N NQR sensitivity by saturating the line v0 whilst observing the NQR at a frequency v_. The presence of a low magnetic field is shown to improve the conditions for localised NQR observations. 
  Reference    Z. Naturforsch. 47a, 430—438 (1992); received July 18 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0430.pdf 
 Identifier    ZNA-1992-47a-0430 
 Volume    47 
73Author    D. Ya, V. L. Osokin, R. H. Ermakov, V. A. Kurbanov, ShagalovRequires cookie*
 Title    The Quasistationary States in Multipulse NQR  
  Reference    Z. Naturforsch. 47a, 439—445 (1992); received August 10 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0439.pdf 
 Identifier    ZNA-1992-47a-0439 
 Volume    47 
74Author    Hideaki Chihara, Koichi ManoRequires cookie*
 Title    Recent Development of Nuclear Quadrupole Resonance Spectra Database  
 Abstract    The Nuclear Quadrupole Resonance Spectra (NQRS) Database contains all the numerical data of resonance frequencies that have been published since 1950, the year NQR was discovered, through the end of 1989. The total number of records compiled is 10,155 as of May, 1991. One record usually covers data of a particular polymorphic modification of a crystalline substance. About 3/4 of all the records deal with organic or organometallic substances. Recent changes in the data content and format, development of online and stand-alone search software, statistics of the database, and updating problems are described. A personal computer version of the database with load/search software was prepared and is described in the Appendix. 
  Reference    Z. Naturforsch. 47a, 446—452 (1992); received August 3 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0446.pdf 
 Identifier    ZNA-1992-47a-0446 
 Volume    47 
75Author    S. A. Lifits, S. I. Anisimov, J. Meyer-Ter-VehnRequires cookie*
 Title    Shock Waves produced by Impulsive Load: Equation of State Effects  
 Abstract    A numerical study of the flow after impulsive load of a plane material surface is carried out. It is shown that the flow is asymptotically self-similar provided one can neglect the cold components in the equation of state. In this case the effective exponent s(r) = d ln(Xs)/d ln(r), derived from the shock trajectory X s (t) does not depend on the initial pressure pulse and approaches the exponent a of the self-similar problem for time t-* oo. For equations of state containing a cold pressure term, s (r) is larger than a and changes non-monotonically with time. Some features of the flow related to the presence of cold components in pressure and internal energy are discussed. 
  Reference    Z. Naturforsch. 47a, 453—459 (1992); received September 9 1991 
  Published    1992 
  Keywords    Shock wave, Impulsive load, Equation-of-state, High pressure, Self-similar flow 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0453.pdf 
 Identifier    ZNA-1992-47a-0453 
 Volume    47 
76Author    H. KleykampRequires cookie*
 Title    X-ray Emission Wavelengths of Argon, Krypton, Xenon, and Curium  
 Abstract    The wavelengths of the L series of argon, krypton and xenon, the K series of argon, and the M series of curium were measured by means of wavelength dispersive X-ray microanalysis. The spec-imens for the investigations were TiC layers which had been HF sputtered under reduced argon pressure by the PVD method, krypton and xenon implanted zeolites, and a curium doped borosil-icate glass. The obtained relative intensities of the X-ray emission lines were normalized to the maximum intensity of the line of the respective series. 
  Reference    Z. Naturforsch. 47a, 460—462 (1992); received October 24 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0460.pdf 
 Identifier    ZNA-1992-47a-0460 
 Volume    47 
77Author    E. Pitt, A. Scharmann, T. SuprihadiRequires cookie*
 Title    The Role of Singlet Oxygen in the Lyoluminescence of Saccharides  
 Abstract    Lyoluminescence, the radiation induced light emission during the dissolution of irradiated solid substances like alkali halides, saccharides, amino acids etc. was proposed as a method of dosimetry. It is established that lyoluminescence is a consequence of a reaction of radicals from radiolysis with oxygen dissolved in the solvent. The role of oxygen in the lyoluminescence of saccharides has been investigated. It has been proved that oxygen is not only necessary for the chemical reaction preceed-ing the lyoluminescence process, but that it is also the emission centre itself. Singlet oxygen is released from the disproportionation of peroxyl radicals produced during solution. The lyoluminescence emission peaks may be attributed to the simultaneous transitions [^gH 1 ^], [^Jl 1 ^] and l 1 !^]! 1 ^] to [ 3 Z~][ 3 2;~] of collisional pairs of singlet oxygen molecules. 
  Reference    Z. Naturforsch. 47a, 463—468 (1992); received December 6 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0463.pdf 
 Identifier    ZNA-1992-47a-0463 
 Volume    47 
78Author    W.-H Steeb, C. M. VilletRequires cookie*
 Title    On Lower Bounds for the Free Energy of the Hubbard Model  
 Abstract    Two lower bounds for the free energy of the Hubbard model are compared. One of the basic tasks in quantum statistics is the calculation the grand thermodynamic potential Q or Helmholtz free energy F for a given Hamiltonian-operator H. In almost all cases the free energies can-not be exactly calculated. Thus it is helpful to find upper and lower bounds for the free energies. Upper bounds are mainly based on the inequality [1, 2] . Ä Ä 
  Reference    Z. Naturforsch. 47a, 469—470 (1992); received December 13 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0469.pdf 
 Identifier    ZNA-1992-47a-0469 
 Volume    47 
79Author    A. Kawski, Z. Gryczyński, I. Gryczyński, J. KuśbaRequires cookie*
 Title    Directions of the Electronic Absorption Transition Moments in «-Substituted 4-Dimethylamino-trans-Styrenes  
 Abstract    Absorption transition moment directions of the diphenylphosphinyl (2 a) and methylsulphonyl (3 a) co-substtuted in 4-dimethylamino-trans-styrenes were determined in stretched poylvinyl alcohol (PVA) films based on measurements of the absorption anisotropics. It has been found that the long-wave absorption spectrum consists of two bands corresponding to differently directed transi-tion moments. The transition moment of the intensive long-wave *La band is lies along the long axis of these molecules whereas that of the short-wave band is oriented at (p = 38° for 2 a and q> = 35° for 3 a relative to the transition moment direction of the 1 La band. 
  Reference    Z. Naturforsch. 47a, 471—474 (1992); received December 7 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0471.pdf 
 Identifier    ZNA-1992-47a-0471 
 Volume    47 
80Author    Hans Bürger, Ralf Kuna, Gottfried Pawelke, Silvia Sommer, Walter ThielRequires cookie*
 Title    High Resolution FTIR Study of the v 8 Band and ab initio Calculation of the Harmonic and Anharmonic Force Field of Difluoromethanimine, CF 2 NH  
 Abstract    The v8 band of CF2NH near 830 cm" 1 has been measured with a resolution of 0.003 cm" 1 and rotationally analyzed. The band is unperturbed, and its rovibrational parameters are given up to fourth order. Theoretical harmonic and anharmonic force constants have been calculated at the 6-31 G** SCF level, and all vibration-rotation interaction constants ctt and anharmonicity constants xu are predicted. The theoretical results are compared with the available experimental data. 
  Reference    Z. Naturforsch. 47a, 475—479 (1992); received November 18 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0475.pdf 
 Identifier    ZNA-1992-47a-0475 
 Volume    47 
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