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1	Author	C. Larke	Requires 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

2	Author	TiloB. Lasberg, D.Ieter Suter	Requires 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

3	Author	B. Bliimich	Requires 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

4	Author	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

5	Author	J. Seliger, V. Ž. Agar, R. Blinc	Requires 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

6	Author	H. Robert, D. Pusiol	Requires 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

7	Author	M. Ariusz, M. Aćkow Iak, M. Arek Bojarski	Requires 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

8	Author	O. Tte R, K. K., Ze Lm, G. M., Je Rb, A. Seegera	Requires 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

9	Author	G. L. Petersen, P. J. Bray, R.A M Arino	Requires 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

10	Author	B. C. Sanctuary, M. Angala, S. K. Rish, N. An	Requires 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

11	Author	M. Baldus, T. O. Levante, B.H M Eier	Requires 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

12	Author	PascalP M An	Requires 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

13	Author	U. Rm	Requires 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

14	Author	H. Anspeter, H. Uber	Requires 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

15	Author	G. Erald Frantz, Hagen Dufner, P. C. Schmidt	Requires 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

16	Author	P. W. Fowler, H. M. Kelly	Requires 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

17	Author	P. Blaha, K. Schwarz, P. Dufek, G. Vielsack, W. Weber	Requires 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

18	Author	E.A C Lucken	Requires 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

19	Author	MichaelH P Alm Er1, JohnA B Lair-Fish2	Requires 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

20	Author	MichaelH P Alm Er3, JohnA B Lair-Fishb	Requires 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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