bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theory of NQR Pulses
Authors: Sanctuary B. C. , Krishnan Mangala S. 
Published: February 2015

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 I = 3 / 2 in an axially symmetric electric field gradient (EFG).
Numerical Simulation of Magnetic Resonance Experiments: Concepts and Applications to Static, Rotating and Double Rotating Experiments
Authors: Baldus M. , Levante T. O. , Meier B. H. 
Published: February 2015

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. Applications to magic angle spinning and double rotation are discussed.
A Theoretical Study of the Vibrational Dependence of the Nuclear Quadrupole Coupling Constants of some Diatomic Molecules
Authors: Lucken E.A.C. 
Published: February 2015

Abstract
The nuclear quadrupole coupling constant was calculated as a function of inter nuclear distance for nine quadrupolar nuclei in eight diatomic 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.
Crystal Structure and NQR of Two Copper (I) Complexes of 4,6-Dimethylpyrimidine-2-thione
Authors: Ramaprabhu Sundara , Lucken Edwin A. C. , Bernardinelli Gérald 
Published: February 2015

Abstract
The crystal structure and 63Cu NQR spectra of two neutral hexanuclear Cu(I) complexes of 4,6-dimethylpyrimidine-2-thione, (Hdmpt); [dmptCu]66CHCl3 (l) and [dmptCu]6C2H4Cl2 (2), are reported. The number and relative intensities of the NQR resonances are in agreement with the results of the crystallographic study. The temperature-dependence of the resonances reveals that both compounds undergo a phase-change in the temperature range 77 K -300 K, both of which may be associated with the loss of a symmetry-element present in the high-temperature phase. The 35Cl resonances of CHCl3 in 1 could be observed in the low-temperature phase but the corresponding resonances for C2H4Cl2 in 2 were not detected.
63,65Cu and 79,81Br NQR Studies of Halogenocuprate Complexes of Triphenylphosphine
Authors: Ramaprabhu Sundara , Amstutz Nahid , Lucken Edwin A. C. 
Published: February 2015

Abstract

63,65Cu and 79,81Br spectra of halogenocuprate (I) complexes containing [CuPPh3 X2]- (X = Cl, Br, I) anions with different cations were recorded in the range 77 K -300 K. The results confirm the previous trend that, for a given ligand, 63Cu NQR frequencies are in the order Cl> Br > I. 63Cu NQR frequencies in [CuPPh3 X2]- are compared with those in neutral Cu(Ph3)2 X(X = Cl, Br) complexes and with the [CuX2]- (X = Cl, Br) anions, other three-coordinate Cu(I) complexes.
Tetraguanidium Hexabromocadmate, [C(NH2)3]4[CdBr6]. Crystal Structure and Bromine Nuclear Quadrupole Resonance
Authors: Krishnan V.G. , Dou Shi-qi , Weiss Alarich 
Published: February 2015

Abstract
The 79, 81Br NQR spectra of tetraguanidinium hexabromocadmate, [C(NH2)3]4[CdBr6] have been studied as a function of temperature from 77 K to 390 K and the crystal structure of the compound was determined at room temperature. The title compound crystallizes monoclinic, P21/c, with four formula units in the unit cell, a = 839.2(3) pm, b = 1895.8(6) pm, c= 1527.4(5) pm, β= 108.14(1)°. The anion [CdBr6]4⊖ is an isolated octahedron, with bond lengths 275≤d(Cd-Br)/pm ≤ 281, and bond angles 88 ≤(Br-Cd-Br)/° ≤95, slightly distorted by hydrogen bonds N -H ··· Br. The 81Br NQR sextet, in dependence from temperature, shows positive and negative temperature coefficients. At 77 K the 81Br NQR frequencies have been found between 42.42 MHz and 31.99 MHz; the 79Br NQR at the frequencies expected from the nuclear quadrupole moment ratio Q(79Br)/Q(81Br). Relations between the 81Br NQR spectrum, the crystal structure, and the hydrogen bonds are discussed.
Ionic Dynamics in Plastic Crystal KNO2 Studied by 39K and 15N NMR
Authors: Kenmotsu Motoko , Honda Hisashi , Ohki Hiroshi , Ikeda Ryuichi , Erata Tomoki , Tasaki Akira , Furukawa Yoshihiro 
Published: February 2015

Abstract
The spin-lattice relaxation time of 39K NMR observed in the low-temperature phase (T<264.1 K) of KNO2 is explained by the quadrupole mechanism contributed from a newly found NO2
- motion. The in-plane C3 reorientation and the overvall NO2 rotation as well as the self-diffusion were shown in the intermediate phase (T ≤ 314.7 K) and the high-temperature plastic phase (T < melting point: 710 K), respectively, by observing 39K and 15N NMR relaxation times and 15N lineshapes.
Successive Phase Transitions and High Ionic Conductivity of Trichlorogermanate (II) Salts as Studied by 35C1 NQR and Powder X-Ray Diffraction
Authors: Yamada K. , Isobe K. , Okuda T. , Furukawa Y. 
Published: February 2015

Abstract
A series of trichlorogermanate(II) salts (AGeCl3, A = Rb, Cs, CH3N H3, and (CH3)4N) have been synthesized and characterized by 35Cl NQR , 35Cl NMR , AC conductivity, DTA, and X-ray diffraction techniques. In the temperature range studied two, two, five, and four phases were confirmed for the Rb, Cs, CH3NH3, and (CH3)4N salts, respectively. From the 35Cl NQR and structural data, isolated pyramidal GeCl3 anions were recognized in the low temperature phases. With increasing temperature the relaxation times of the 35Cl NQR decreased exponentially and the signals disappeared far below the melting point. This suggests that the reorientation of the anion about the pseudo three-fold axis is excited. With further increase in temperature, the ionic conductivity of CH3NH3GeCl3 and (CH3)4NGeCl3 increased drastically at the phase transitions to their cubic perovskite phases (CH3NH3GeCl3:σ= 10-1 Sm-1 at 400 K, (CH3)4NGeCl3: σ = 5 x 10-2 Sm-1 at 420 K). The mobile ion was confirmed to be the chloride ion by means of 35Cl NMR and X-ray diffraction.
Phase Transitions in 4,4´-Dichlorobenzophenone as Studied by 35Cl FT-NQR
Authors: Nakayama Hirokazu , Eguchi Taro , Nakamura Nobuo 
Published: February 2015

Abstract
The temperature dependence of 35Cl NQR frequencies in 4,4´-dichlorobenzophenone was measured between 9.3 and 372 K by the pulse Fourier-transform method. Successive phase transitions were observed at 189 and 194 K. Concerning these phase transitions, the curious thermal hysteresis phenomenon found in a previous NQR experiment was not reproduced in the present study. It also follow s that NQR indicates another phase transition around 220 K, although no thermal anomaly was detected there by DTA. Tentative explanations for these three phase transitions are presented in relation to the incommensurability between 189 and 220 K. In addition, a novel phase transition was found to occur at 331 K according to both DTA and 35Cl NQR. A single NQR line observed at room temperature splits into two components above 331 K, suggesting that the symmetry above 331 K is lower than that at room temperature. This is the behavior of re-entrant phase transition, and it reveals the quasi-continuous nature.
Inequivalent Reorientation of the Trichloromethyl Groups in 1,4-Bis(TrichloromethyI) Benzene as Studied by Pulsed 35Cl NQR
Authors: Niki Haruo , Odahara Hirotaka , Tamaki Katsuji , Hashimoto Masao 
Published: February 2015

Abstract
The temperature dependence of T1 of 35Cl NQR of the title com pound evidenced that the three crystallographically inequivalent CCl3 groups have different potential barriers against reorientation (about 30, 36, and 42 kJ/mol). An intramolecular interaction between π-electrons on the benzene ring and the C -Cl bond is proposed to interpret the characteristic frequency splitting common to the 35Cl NQR spectrum of each of the three inequivalent CCl3 groups. The magnitude of T2 of each Cl atom is interpreted by intra-and intermolecular H ··· Cl interactions. It was found that only part of the temperature dependence of the NQR frequency can be interpreted by reorientation.
35Cl NQR Relaxation and Hydrogen Bond in Some Chloral Hemiacetals
Authors: Hashimoto Masao , Matsumoto Shuji , Kunitomo Masakazu , Niki Haruo , Odahara Hirotaka , Tamaki Katsuji 
Published: February 2015

Abstract
The crystal structure of chloral ethylhemiacetal has been determined at 291 K: monoclinic, space group C2
2 - P21, Z = 2, a = 854.5(1), b = 594.0(3), c = 853.3(1) pm, β = 108.30(2)°, R = 0.0962. A sharp decrease of the spin lattice relaxation time T1 found for the 35Cl NQR of the CCl3 groups in chloral methyl-, ethyl-and n-heptylhemiacetals is attributed to the onset of reorientation of the group over a potential barrier o f ca. 39, 37, and 32 kJ/mol, respectively. An unusual T1 vs. 1/T curve with a T1 minimum superimposed on the sharp decrease of T1 due to the reorientation was observed for each of the three 35Cl NQR lines of nHp-CH . This phenomenon is tentatively ascribed to a fluctuation of EFG caused by jumping motion of the hydrogen atom s in the OH groups.
Ionic motion and Disordered Structure in the Rotator Phase of Butylammonium Chloride Studied by Temperature Dependences of 35Cl and 2H NMR
Authors: Hattori Mineyuki , Onoda Yoshito , Erata Tomoki , Smith M.E. , Hattori Masakazu , Ohki Hiroshi , Ikeda Ryuichi 
Published: February 2015

Abstract
Temperature dependences of 35Cl and 2H quadrupole coupling constants and 35Cl NMR spin-lat­tice relaxation times in polycrystalline samples were measured in the rotator phase of the butylammonium chlorides C4H9NH3C1 and C4H9ND3C1, obtainable above the phase transition temperature of 241 K. A rapid decrease o f the quadrupole coupling constants of both nuclei upon heating is attributed to increasing dynamic disorder formed around the polar head. The presence of self-diffussion of Cl- ions was revealed from the spin-spin relaxation time and resonance line-width in single crystals, and confirmed by measuring the dc electrical conductivity.
NQR Spin-Lattice Relaxation of Re in Perrhenates
Authors: Szabo A.J. , Brown R. J. C. 
Published: February 2015

Abstract
The temperature dependence of the spin-lattice relaxation time T1 for the Re NQR in KReO4 , NH4ReO4 and ND4ReO4 has been measured between 77 K and 323 K. The relaxation is electric quadrupolar in all cases, and because of the large quadrupole moment of Re, T1 is short. In KReO4 T1 follows a T2 dependence. In NH4ReO4 , T1 decreases more rapidly than T-2 above about 100 K; between 170 K and 250 K T1 is smaller than 100 (is and could not be measured, but above 250 K, T1 increases to about 140 μs, and the measured data near room temperature lie close to the T-2 extrapolation from the T1 values below 100 K. These results are interpreted as normal anharmonic Raman quadrupolar relaxation, with a T-2 dependence on temperature, combined with an additional relaxation process due to switching of the ammonium ion between two possible orientations.
Nuclear Quadrupole Interaction and Ionic Dynamics in Sodium Superionic Conductors
Authors: Nakamura Nobuo 
Published: February 2015

Abstract
Recent work on the 23N a quadrupole interaction in the NASICON family is reviewed. The applicability and the limitation of the two-dimensional nutation NMR to complex systems with more than one quadrupolar nuclear sites is discussed and the possibility of sodium ion exchange in some of the NASICON-type com pounds is pointed out. The microscopic mechanism of the site exchange is examined by molecular dynamics simulation. A model potential energy function for the site exchange and /or hopping transport o f the sodium ions is proposed. It interprets qualitatively the difference between the activation energies deduced by NMR and by conductivity measurement.
The Energy Dispersion of the Chain Band in YBa2Cu3O6+x and Its Effect on the Cu(2) NQR Frequency
Authors: Eremin M. V. , Markendorf R. , Solovjanov S. G. 
Published: February 2015

Abstract
The energy dispersion of the chain band has been determined in the framework of the Hubbard model. The results are in agreement along the ⌈-S and ⌈ -Y lines of the Brillouin zone with photoemission data. The amount of d3z
2
-r
2 states is zero at y = 0 and increases to 10% at y = 1. The admixture is due to the hybridization of C u (l) dy
2
-z
2 states with Cu(2) d3z
2
-r
2 states via apical oxygen. The effect of this admixture on the NQR frequency of Cu(2) is discussed.
Local Magnetic Fields in some Bismuth Compounds. A Survey of Experimental Evidences
Authors: Kravchenko E. A. , Orlov V. G. 
Published: February 2015

Abstract
The splittings observed in the 209Bi nuclear quadrupole resonances of α-Bi2O3, in zero magnetic field, follow the typical pattern of a Zeeman perturbed NQR spectrum. The lineshapes in Bi3O4Br also indicate a poorly resolved splitting that points to the presence of an internal magnetic field in the order of 200 G. This exceeds notably the dipole nuclear magnetic fields (about several G), but is orders of magnitude smaller than paramagnetic fields produced by unpaired electron spins.
The results obtained using a SQUID and μSR-technique can also be interpreted as indicative of magnetic properties not conventionally expected in such compounds.
The Influence of Reverse Nonradiative Excitation Energy Transfer on the Fluorescence Spectra of Two-component Fluorescent Solutions
Authors: Bojarski  , Kawski A. , Kukliński B. , Diehl H. 
Published: February 2015

Abstract
The reverse non-radiative excitation energy transfer (RNEET) in the system of rhodamine 6G (R6G, donor) and rhodamine B (RB, acceptor) is investigated. The presence of RNEET from the energy acceptors to the energy donors is dem onstrated using steady-state fluorescence and fluorescence anisotropy techniques. The spectra are deconvoluted and obtained results are analysed.
Photoselection of Luminescent Molecules in Anisotropic Media in the Case of Two-Photon Excitation. Part I. Theoretical Considerations
Authors: Kawski A. , Piszczek G. 
Published: February 2015

Abstract
Photoselection of elongated luminescent molecules oriented in a stretched polymer film is considered theoretically for the case of two- and three-photon excitation, having in mind the employment of this phenomenon for determining the angle between the absorption and emission transition moments. Two-photon photoselection provides information on electronic excited states which are not detectable by conventional one-photon spectroscopy due to selection principles.
ESR of Gamma Irradiation Damage Centers in Single Crystals of Thriethanolamine Hydrochloride
Authors: Birey Mehmet , Aktas Huseyin , Zengin D. Mehmet 
Published: February 2015

Abstract
We have observed two radicals in the ESR spectra of y-irradiated single crystals of thriethanolamine hydrochloride: R -ṄH and HN = Ċ - R .
Dielectric Properties of 4-Cyanobiphenyl in 1,4-Dioxane Solution
Authors: v. Homhardt S. , Stockhausen M. , Jadżyn J. , Kędziora P. , Ghoneim A. , Turky G. 
Published: February 2015

Abstract
The static and dynamic dielectric properties o f the title system are reported for a concentration series from about 8 mmol/1 up to 2.3 mol/I at 20 °C. The apparent moment (4.2 D , extrapolated to infinite dilution) decreases with increasing concentration, the relaxation time increases proportional to viscosity, that is, somewhat steeper than usually observed. Com parison with other molecules suggests that these features are mainly due to the high dipole moment rather than being specifically related to the prolate shape o f the molecule. The broadening o f the spectrum toward the high frequency side, on the other hand, may be due to the molecular shape.
Relation between NMR Properties and Electrical Resistivity in Li-Ge, Li-Sn and Li-Pb Liquid Alloys
Authors: Xu R. , van der Lugt W. 
Published: February 2015

Abstract
Recent measurements of the electrical resistivity of liquid Li-Ge alloys enable us to check relations between NMR properties and resistivity in non-metallic alloys derived by Warren in 1971. It is shown that the predicted linear relationships hold, but that the proportionality between the square root of the conductivity and the Knight shift is violated to some degree. A possible cause is the neglect of quadrupole interactions. Also, the relations only hold if the composition rather than the temperature is taken as the implicit parameter.
Electron Paramagnetic Resonance of some Irradiated Ammonium Compounds
Authors: Köksal Fevzi , Yavuz Metin 
Published: February 2015

Abstract
Gamma irradiation damage centres in (NH4)2SiF6, (NH4)2SnCl6, (NH4)2PtCl6, [(CH3)2NH2]2SnCl6, (NH4)2PdCl6 and ultraviolet irradiation damage centres in (CH3)4NCH3COO and (CH3)4NBr have been investigated by electron paramagnetic resonance spectroscopy. It has been found that the radicals produced in (NH4)2SiF6 and (NH4)2SnCl6 is N2H4
+ , and those in (NH4)2PtCl6 are NH3
+ and (PtCl6)3-. In [(CH3)2NH2]2SnCl6 the species is (CH3)2NH+ , and in (NH4)2PdCl6 the species is (PdCl6)3 -. Furthermore, it has been shown that the ultraviolet irradia­ tion produces ĊH3 and CO2
- radicals in (CH3)4NCH3COO and ĊH3 radical in (CH3)4NBr. The EPR parameters of the observed radicals have been determined.
On the Enclathration of NaB(OH)4 in the β-Cages of Sodalite: Crystallization Kinetics and Crystal Structure
Authors: Buhl J.-Ch. , Mundus C. , Löns J. , Hoffmann W. 
Published: February 2015

Abstract
The hydrothermal formation of sodium hydroxyborate enclathrated sodalite synthesized from an initial ternary mixture of mullite, cristobalite and corundum has been investigated. Depending on temperature and pressure the compound Na7.5[AlSiO4]6[B(OH)4]1.5 · 2H2O could be synthesized in form of polycrystalline powder as well as in form of single crystals. The kinetics of the sodalite growth could be determined at 423 K and 473 K. 29Si-and 27Al MAS NMR was shown to be the preferred method to describe the conversion into sodalite quantitatively. Evidence for the first formation of polycrystalline sodalite has been found after the total dissolution of mullite and cristobalite.
Single crystal X-ray diffraction data were used for the structure determination and refinement. The position and orientation of the hydroxyborate anions within the sodalite's /β-cages could only be found in the course of a "rigid body" refinement with constraints for the B(OH)4 tetrahedron. The boron atoms are located in an off-centre position within the sodalite cages. One out of the four oxygen atoms of the hydroxyborate group is positioned near the centre of a face of the sodium tetrahedron, whereas the three remaining oxygen atoms are near to the middle of its edges.
Mössbauer Studies of Nickel-Iron Hydrotalcites
Authors: Pegelow U. , Winterer M. , Mosel B. D. , Schmalzb M. , Schöllhorn R. 
Published: February 2015

Abstract
Hydrotalcite-like Fe-Ni-hydroxides [Ni2/3
IIFe1/3
III(OH)2](CO3)1/6(H2O)y , [Ni3/4
IIFe1/4
III(OH)2]-(CO3)1/8(H2O)y and [Ni3/4
II/IIIFe1/4
III(OH)2](CO3)0.14(H20)y as well as the ternary oxide NaNi2/3Fe1/3O2 have been studied by 57Fe-Mössbauer spectroscopy. All samples contain Fe3+ in a high spin state. The quadrupole interaction is smaller if a magnetic splitting is present, which may indicate a non-parallel arrangement of the principal axis of the EFG and the hyperfine field. The temperature dependence of the spectra has been understood in terms of collective cluster excitations. In this model the magnetic energy of a single domain depends on the direction of the total magnetic moment and on magnetic interaction with the neighbourhood. The spectral lineshape could be fitted assum­ing uniaxial relaxation.
From Dispersion to Laminarity in Dynamical Systems
Authors: Zumofen G. , Klafter J. 
Published: February 2015

Abstract
We study transport in dynamical systems characterized by intermittent chaotic behavior with coexistence of dispersive motion due to periods of localization, and of enhanced diffusion due to periods of laminar motion. This transport is discussed within the continuous-time random walk approach which applies to both dispersive and enhanced motions. We analyze the coexistence for the standard map and for a one-dimensional map.
Theory of linear response applied to the lithium isotope effects on the mobilities in molten LiCl
Authors: Schäfer Lutz , Klemm Alfred 
Published: February 2015

Abstract
Expressions in terms of group-velocity time-correlation functions for the ionic mobilities of molten 6LiCl,7 LiCl and (6Li,7 Li)Cl are derived, taking the time-averaged zero momentum of inertia of each of the three groups of ions into account. MD-simulations have been performed for 6LiCl and 7LiCl, yielding agreement between the simulated and the published experimental reduced isotope effect, although the temperature -volume conditions of the simulations did not conform with natural LiCl.
No Decelerated β-Decay of Tritium Solved in Titanium
Authors: Wicke Ewald 
Published: February 2015

Abstract
Experimental results on the interaction of tritium with fine
particles of titanium, published in Phys. Lett. A and attributed
to decelerated β-decay of tritium solved in titanium, are
instead explained by adsorption of tritium on the surface of
the particles, formation of tritium oxide when oxygen is present,
and normal β-decay.
Finite Larmor Radius and Hall Effects on Thermal Instability of a Plasma in Porous Medium
Authors: Sharma R. C. , Bhardwaj V. K. 
Published: February 2015

Abstract
The thermal instability of a plasma in a porous medium in the presence of a finite Larmor radius (FLR) and Hall effects is considered. Oscillatory m odes due to the presence of a magnetic field (and hence the presence of FLR and Hall effects) are introduced. For stationary convection, the FLR may have a stabilizing or destabilizing effect, but a completely stabilizing one for a certain wave-number range. Similarly, the Hall currents may have a stabilizing or destabilizing effect but a completely stabilizing one for the same wave-number range under certain condition, whereas the medium permeability always has a destabilizing effect for stationary convection.
Einfluß des Silberkations auf das Fluoreszenzverhalten polyzyklischer aromatischer Kohlenwasserstoffe
Authors: Komfort Michael , Küster Jörn , Dreeskamp Herbert 
Published: February 2015

Abstract
Combining the results of fluorescence and triplet-triplet absorption measurements, the influence of silver perchlorate on the excited states of pyrene, phenanthrene, 9-cyanophenanthrene, 9,10-diphenylanthracene and 9,10-dicyanoanthracene in fluid solutions has been investigated. In corre­ spondence with a small energy gap between the lowest excited singlet state and the nearest lower triplet state an external heavy atom effect has been found to be responsible for the fluorescence quenching in the case of pyrene, phenanthrene and 9-cyanophenanthrene. In the case of 9,10-diphenylanthracene and 9,10-dicyanoanthracene, where this energy gap is large, an exciplex emission is observed with no significant increase of triplet state formation. Furthermore, 9-cyanophenanthrene and 9,10-dicyanoanthracene under similar experimental conditions form ground state complexes with AgCIO4 with a red-shifted fluorescence. From time-resolved fluorescence measurements a dynamic equilibrium of association in the excited state is deduced.