bluuebunny/crossref_metadata_2025_split huggingface dataset:
63Cu NQR Studies of Two-and Three-coordinated Complexes of Cu(I) with Siloxyl Ligands
Authors: Khajehnouri Fereidoun , Motallebi Shahrokh , Lucken E. A. C. 
Published: February 2015

Abstract
We report the 63Cu NQR spectra of seven two-and three-coordinated complexes with the siloxyl ligand. R3SiO-. The frequencies are compared to those of other two- and three-coordinated species, and it is demonstrated that the partial field gradient of the R3SiO- group is very similar to that of Cl-.
Electronic Characteristics of Sn-Hal Bonds in Hexa-and Pentacoordinate Tin(IV) Adducts of Type RnSnHal4-nLx
Authors: Kravchenko E.A. , Burtzev M.Yu. 
Published: February 2015

Abstract
The σ-and π-electron effects of alkyl/phenyl substituents on the Sn-Hal bonds in penta- and hexacoordinate tin(IV) chloro and iodo adducts are discussed based on their 35Cl and 127I NQR spectra. Unexpectedly high 127I EFG asymmetry parameters were found in most dialkyl(phenyl)-substituted adducts of thin(VI) iodides.
Electric Field Effect on NQR in Ferroelectric Materials
Authors: Jung Jae Kap , Kim Hae Jin , Han Kee Tae , Choh Sung Ho 
Published: February 2015

Abstract
The electric field effect on NQR in ferroelectric materials, 93Nb in LiNbO3 and 14N in NaNO2 and SC(NH2)2 , has been investigated at 77 K. In these crystals with single domain, only the line shift due to the external electric field was observed. In the case of NaNO2 powder and a crystal with multi-domains, line broadening was observed in the external electric field. These phenomena can be explained with the fact that the direction of spontaneous polarization in a domain is related to the direction of the applied electric field. The rate of the NQR line-shift due to the electric field is remarkably smaller in mostly ionic crystals, such as LiNbO3 and NaNO2 , than in a molecular crystal such as SC(NH2)2 . This is due to the strong ionic bonding in ionic crystals. Also, the difference of the Stark shift'between NaNO2 and SC(NH2)2 is discussed in terms of the local electric field and polarizability at the resonant nuclear site.
23Na Spin-Lattice Relaxation Measurements in Dehydrated Na-X Zeolite
Authors: Igarashi Mutsuo , Okubo Noriaki , Hashimoto Shuichi , Cha Deok Joon , Yoshizaki Ryozo 
Published: February 2015

Abstract
The spin-lattice relaxation time T1 of 23Na-NMR in a dehydrated Na-X zeolite has been measured from 20 to 300 K. The recovery curve is not single-exponential at all measured temperatures and T1
-1 increases with the square of temperature around room temperature. The results are analyzed by assuming non-equivalent sites and by applying the theory of the Raman process based on covalency.
Magnetic Properties of the Bismuth Oxide α — Bi2O3
Authors: Kharkovskii A.I. , Nizhankovskii V.l. , Kravchenko E. A. , Orlov V. G. 
Published: February 2015

Abstract
A very unusual magnetic behaviour of α - Bi2O3 was observed in a wide range of temperatures and magnetic fields. A longitudinal magnetoelectric effect was found at 4.2 K. The existence of an antiferroelectrically ordered subsystem of electric dipoles in α - Bi2O3
is proposed. The mechanism of spin-orbit coupling is regarded as the physical origin for the occurrence of the ordered magnetic moments in α - Bi2O3.
An NQR Study of Inclusion Compounds Formed Between Small Chlorine-containing Molecules and bis(N-alkylimidazolidine-2-thione)Cu(I) Halide Complexes
Authors: Zhao Ya-Nan , Ramaprabhu Sundara , Lücken Edwin A.C. 
Published: February 2015

Abstract
Twenty-five inclusion complexes formed by bis(N-alkylimidazolidine-2-thione)cuprous halides with the small, chlorine-containing guest molecules CCl4, CHCl3, CH2Cl2, CH3CCl3 or C2H2Cl2 , have been prepared. Their 63Cu and 35Cl NQR spectra have been measured over the temperature range 77-300 K. For the corresponding bromides the 79Br and/or 81Br spectra have also been investigated. The studies reveal the number and symmetry of different inclusion site. The onset of rapid reorientation of the guest molecules is indicated by the fading out of their NQR signals between 77 and 300 K, whereas the resonances from the host molecules usually persist throughout this temperature range. However, as evidenced by discontinuities in the temperature-dependence of the NQR frequencies of the hosts, sixteen of the complexes show one or more phase-changes in this temperature-range.
Structure and Successive Phase Transitions of RGeBr3 (R = Alkylammonium) Studied by Means of NQR
Authors: Gotou Shusaku , Okuda Tsutomu , Takahashi Toshirou , Terao Hiromitsu , Yamada Koji 
Published: February 2015

Abstract
A series of tribromogermanate(II) complexes RGeBr3 (R = CH3NH3, (CH3)2NH2, (CH3)4N, C2H5NH3, (C2H5)4N) have been synthesized and characterized by 81Br NQR, AC conductivity, DTA, and X-rax diffraction. These measurements revealed the presence of successive phase transitions in these complexes. The crystal structures of Phases I and II in (NH3)4NGeBr3 were derived from the Rietveld analysis of powder X-ray diffraction. The electric conductivity was considerably high in CH3NH3GeBr3 and (NH3)4NGeBr3. The conduction mechanism is discussed on the basis of 81Br NQR spin-lattice relaxation times and crystal structures.
Motion of Water Molecules and Hydrogen Bonds in Zinc Hexachlorostannate (IV) Hexahydrate as Studied by 1H NMR and 35Cl NQR
Authors: Ishikawa A. , Sasane A. , Hirakawa Y. , Mori Y. 
Published: February 2015

Abstract
The 1H NMR spin-lattice relaxation time T1, 35Cl NQR frequency νQ, and 35Cl NQR spin-lattice relaxation time T1Q of [Zn(H2O)6] [SnCl6] (zinc hexachlorostannate(IV) hexahydrate) have been measured at temperatures between 77 and 350 K. The NQR spin echo signal with νQ = 15.689 MHz at 77 K showed a positive temperature coefficient attributable to O-H-Cl type H-bonds in the crystal. νQ at 77 K is strongly correlated with the electronegativity χM of the metal M in the series of stannates [M(H2O)6] [SnCl6] (M = Mg, Ca, Mn, Co, Ni, Zn). A T1 minimum observed for the Zn salt is ascribed to 180° flips of water molecules with an activation energy of 20 kJ mol-1. The motion is influenced by repulsive forces among the water molecules within a cation rather than by attractive forces between the H-bonded H and CI atoms. T1Q proved to be mainly governed by lattice vibrations, weakly modulated by the fluctuating electric field gradient caused by the 180° flip motions.
Anharmonic Librations and the Temperature Dependence of NQR Frequencies
Authors: Mendonça Christovam , Rabbani Said R. 
Published: February 2015

Abstract
The temperature dependence of NQR frequencies of nuclei in molecules undergoing quasi-har-monic rotational oscillations is calculated. Following the model proposed by Bayer, the instanta-neous orientation of the electric field gradient principal axes is assumed to change from its average orientation as a result of rotational oscillations, while the EFG magnitude remains constant. The eigenstates and energy eigenvalues of a rotator in a potential of the form V(θ)= V2θ2 - K4θ4 are calculated by standard perturbation methods, followed by the evaluation of statistical averages of square angular amplitudes. For molecular crystals with more than one molecule in a unit cell the angular displacements are expressed in terms of normal coordinates, and the same procedure is followed. The final expression for the change in the NQR frequency consists of two terms, the first one being related to the harmonic part of the potential and the second one to the quartic term. At the absolute zero it yields a nonzero contribution to ⟨θ2⟩, and for high temperatures it reproduces the nonlinear character of νQ(T) observed experimentally. The model has been tested with measure-ments on solid Cl2 performed by Nakamura and Chihara, combined with libration mode frequencies measured in Raman spectroscopy by Cahill and Leroi and analysed according to our anharmonic libration picture. The fitting of our equation to experimental data supports Cahill and Leroi's hypothesis about the existence of an undetected libration mode in Cl2 Raman spectra of frequency near 60 cm- 1
Successive Phase Transitions in Potassium Hexachloroselenate(IV) Revealed by 35Cl NQR
Authors: Asaji Tetsuo , Ohkawa Masaki , Chiba Takehiko , Kaga Makoto 
Published: February 2015

Abstract
K2SeCl6 undergoes structural phase transitions of first order at 35 K, 65 K, and 79 K. The temperature dependence of the 35Cl NQR spin-lattice relaxation time suggests that the phase transitions at 65 K and 79 K are displacive ones associated with a resonant soft mode. The presence of a precursor cluster is suggested by the temperature dependence of the signal intensity above 79 K.
Anharmonic Lattice Vibrations and the Temperature Shift of Raman Spectral Lines
Authors: Mendonça Christovam , Rabbani Said R. 
Published: February 2015

Abstract
The temperature dependence of the average lattice mode frequency of a molecule undergoing librational motion in a quasi-harmonic potential has been calculated with the purpose of finding an explicit relationship between the observed shift of Raman spectral lines with temperature and the anharmonic term in the rotational potential. Calculations were carried out both for uncoupled and coupled oscillators. The equations obtained with this model provide good fittings for solid Cl2 and benzene data. This result can be applied to the analysis of the temperature dependence of NQR frequencies in molecular crystals.
NQR and NMR Studies of Phase Transitions in R2Pb[Cu(NO2)6] (R = K, Rb, Tl, Cs, and NH4)
Authors: Mizuno Motohiro , Asaji Tetsuo , Suhara Masahiko , Furukawa Yoshihiro 
Published: February 2015

Abstract

39K, 87, 85Rb, 133Cs, 205T1, and 1, 2H NMR spin-lattice relaxation times T1 and 14N NQR spin-lattice relaxation times T1Q were determined for R2Pb[Cu(NO2)6] (R = K, Rb, Tl, Cs, and NH4). T1 of 39K and 87Rb showed very short values in the incommensurate phase as compared with those in the other phases. When the commensurate-incommensurate phase transition point is approached from below, 14N T1Q of the R = K, Rb, Tl, and NH4 compounds showed rapid decrease. On the other hand, that of the R = Cs compound began to decrease first after passing beyond the corresponding transition point. The difference of the T1Q behavior may be ascribed to the difference of the condensed phonon mode in the incommensurate phase.
Chlorine NQR and Phase Transitions in NOCl
Authors: Pirnat J. , Trontelj Z. , Borrmann H. 
Published: February 2015

Abstract
Chlorine NQR studies of solid nitrosyl chloride NOCl at temperatures below 200 K were undertaken. They indicate an ionic character of the N-Cl chemical bond and confirm the phase transition near 140 K. Thermal hysteresis of the transition temperature was observed.
Phase Transition of C5H5 NHSbBr4 Having a Hypervalent Bond: A 2H NMR and X-Ray Diffraction Study [Phase Transition of C5H5NHSbBr4]
Authors: Yamada K. , Ohtani T. , Shirakawa S. , Ohki H. , Okuda T. , Kamiyama T. , Oikawa K. 
Published: February 2015

Abstract
The second order phase transition at 253 K of pyridinium tetrabromoantimonate(III), C5H5NHSbBr4 , has been characterized by means of X-ray diffraction and 2H NMR. As was suggested from the 81Br NQR spectra, the Rietveld refinements of the X-ray diffraction patterns at 297 K and 116 K confirm the structural change of the anion from SbBr-
4 to SbBr3 • Br-. The line shape analysis of the 2H NMR using the deuterated analog revealed that the librational amplitude of the pyridinium ring about the axis normal to the plane increased with temperature and its rms amplitude reaching ca. 25° at Tc . The librational motion may induce the phase transition breaking the hydrogen bonds of the type N-H … Br. However, nearest-neighbor 2π/6 jump or reorientation such as seen in benzene were not observed even at 350 K.
Temperature Dependence of 14N NQR and Phase Transitions in KNO2 Powder
Authors: Kim Hae Jin , Han Kee Tae , Choh Sung Ho 
Published: February 2015

Abstract
The temperature dependence of 14N NQR, measured at 77 to 300 K, is in better agreement with the model proposed by Blinc et al. than the Bayer theory. The nuclear quadrupole coupling constant and asymmetry parameter show a discontinuity at about 160 K and 230 K, respectively. The linewidths are broadened at these temperatures up to 22 kHz and 18 kHz, respectively. These results indicate that KNO2 undergoes phase transitions at these two temperatures.
On the Structure of Some Pentaerythritol-Related Molecular Crystals with Pseudotetrahedral Molecular Structure. Ordered Structure of 2,2-Bis(bromomethyl)-1,3-propanediol and Orientationally Disordered Structure of 2-Chloromethyl-2-methyl-1,3-dichloropropane; 35Cl NQR
Authors: Dou Shi-qi , Fuess Hartmut , Strauß Roman , Weiss Alarich 
Published: February 2015

Abstract
C(CH2Cl)3(CH3), melting point Tm = 291.3 K, shows in the DTA/DSC experiment a phase tran-sition from an orientationally disordered plastic phase I into an ordered phase II at TI ⃗ II = 235.9 K. From 77 K up to TII ⃗ I the 35Cl NQR spectrum is a triplet with (ν in MHz, T=77 K) ν1 = 34.213, ν2 = 34.183, ν3 = 33.786. The 35Cl NQR fade-out temperature Tf = 247 K coincides with TII ⃗ I found from the DSC experiment. The plastic phase of 2-chloromethyl-2-methyl-l,3-propanediol is cubic bcc, Im3m, Z = 2 and the lattice constant increases linearly 755 pm at 235 K to 768 pm at 283 K. In the heating cycle we found (ΔH in kJ/mol): ΔHII ⃗ I = 12.0, ΔSm/R = 1.0. The compound belongs to the group of plastic molecules formed by ellipsoid like distorted tetrahedra and is derived by substitution from methane. The crystal structure of 2,2-bis(bromomethyl)-1,3-propanediol was determined. DTA-DSC show that an orientationally disordered plastic phase does not exist. At room temperature C(CH2Br)2(CH2OH)2 crystallizes monoclinic, space group Cc, Z = 4, a = 628.2 pm, 6 = 2015.5 pm, c = 659.6 pm, β = 94.27°. The molecules interact by intermolecular hydrogen bonds between the OH-groups and by van der Waals forces Br…Br.
63Cu-NMR Study in High-Tc Superconductor HgBa2Ca2Cu3O8 + δ
Authors: Magishi K. , Zheng G.-q. , Kitaoka Y. , Asayama K. , Tokiwa K. , Iyo A. , Ihara H. 
Published: February 2015

Abstract
The 63Cu nuclear transverse relaxation rates have been measured in the normal state on both square and pyramidal CuO2 planes in HgBa2Ca2Cu3O8 + δ with Tc = 133K. The Gaussian component of the spin-echo decay rate, 63(1/T2G), for both sites increases with decreasing temperature, followed by a peak around T* ~ 150 K, indicating that the spin correlation becomes stronger with decreasing temperature. Also, it is found that the magnitude of 63(1/T2G) for a square site is larger than that for a pyramidal one, suggesting that the spin correlation in the square plane is stronger than that in the pyramidal one.
Algebraic Schrödinger Representation of Quantum Chromodynamics in Temporal Gauge and Resolution of Constraints
Authors: Stumpf H. , Pfister W. 
Published: February 2015

Abstract
The algebraic formalism of QCD is expounded in order to demonstrate the resolution of Gauß constraints on the quantum level. In the algebraic approach energy eigenstates of QCD in temporal gauge are represented in an algebraic GNS-basis. The corresponding Hilbert space is mapped into a functional space of generating functional states. The image of the QCD-Heisenberg dynamics becomes a functional energy equation for these states. In the same manner the Gauß constraints are mapped into functional space. In functional space the Gauß constraints can be exactly resolved. The resolutions are defined by nonperturbative recurrence relations. The longitudinal color electric energy can be expressed by means of these resolvents, which leads to "dressed" color Coulomb forces in temporal gauge. Although present in the system, the longitudinal vector potentials do not affect its energy eigenvalues. This leads to a selfconsistent subsystem within the functional energy equation in temporal gauge which has to be identified with a functional energy equation in Coulomb gauge. In addition this procedure implies a clear conception for the incorporation of various algebraic representations into the formal Heisenberg dynamics and establishes the algebraic “Schrödinger” equation for QCD in functional space.
Nitrogen Nuclear Quadrupole Interactions in RDX, β-HMX and Cocaine Systems
Authors: Pati Ranjit , Das T. P. , Sahoo N. , Ray S.N. 
Published: February 2015

Abstract
Using the Hartree-Fock-Roothaan procedure, the nuclear quadrupole interactions (NQI) of the 14N (I = 1) nucleus in the energetically important molecules RDX, β-HMX and the physiologically important molecule Cocaine, are studied. The coupling constants (e2 q Q) and asymmetry parameters (η) for the three ring nitrogens in RDX are found to be -5.671, -5.808 and -5.838 MHz and 0.542, 0.556 and 0.562, respectively, in good quantitative agreement with the experimental results of 5.735, 5.799 and 5.604 MHz for the magnitudes of e2qQ and 0.6215, 0.6146 and 0.6024 for η obtained in the single crystal. For β-HMX, where two sets of e2 q Q and η are expected from symmetry considerations, our calculated values are -5.936 and -6.069 MHz for e2 q Q and 0.432 and 0.490 for η , compared to experimentally measured magnitudes of 5.791 and 6.025 MHz and η-values of 0.4977 and 0.5180, respectively, obtained in the single crystal. For Cocaine free base which contains only one 14N nucleus, our calculated values of e2 qQ and η are -5.038 MHz and 0.067, in very good agreement with the experimental results of 5.0229 MHz for the magnitude of e2 q Q and 0.0395 for η. Possible reasons for the small remaining differences between theory and experiment in e2 q Q and η for all three systems and the significant differences in trends over the three nitrogens in RDX between theory and experiment are discussed. Also, the calculated quadrupole interaction parameters for the 14N nuclei in the NO2 groups outside the ring for both RDX and β-HMX are presented with the hope that they will be measured in the future to provide a more complete understanding of the electron distributions in these systems.
X-Ray and 35Cl NQR Studies on the Trichloroacetyl Group in Covalent and Ionic Compounds of L-Valine and DL-Valine
Authors: Ofial A.R. , Dou S.-q. , Krishnan V. G. , Paulus H. , Fuess H. , Weiss Al. 
Published: February 2015

Abstract
The crystal structures and 35Cl NQR of trichloroacetyl-DL-valine (1), trichloroacetyl-L-valine (2), as well as the salts of trichloroacetic acid with DL-valine (3) and L-valine (4) have been investigated. Crystal data are for (1): Monoclinic, C2/c, a= 15.835(4) Å, b= 10.481 (3) Å, c = 14.046(4) Å, β = 103.28(1), Z = 8; (2): Orthorhombic, P212121, a = 12.117(3) Å, 6=10.896(3) Å, c= 8.718(2) Å, Z = 4; (3): Triclinic, P1̄, a= 17.269(3) Å, 6 = 8.504(3) Å, c = 10.427(4) A, a = 105.38(2), β = 96.98(2), γ = 96.24(2), Z = 2; (4): Monoclinic, P21, a = 10.378(4) Å, b = 20.349(8) Å, c= 11.890(5) Å, β = 95.28(2), Z = 8. The onset of rotational motion within the trichloroacetyl groups bleaches out 35Cl NQR lines between 115 K and 185 K for (1)-(4). While TCA-L-valine (1), TCA-DL-valine (2), and TCA(-) · DL-valine(+) (3) do not show any phase transition in the temperature range 77 K to 295 K, TCA(-) · L-valine(+) (4) shows more than one phase transition above 77 K before the three NQR signals bleach out at 164 K.
Neutron and X-ray Diffraction Study on the Structure of Ultraphosphate Glasses
Authors: Hoppe Uwe , Walter Günter , Stachel Dörte , Barz Andrea , Hannon Alex C. 
Published: February 2015

Abstract
The high real-space resolution of neutron diffraction experiments which is provided by use of the epithermal neutrons from spallation sources was exploited in order to differentiate the unlike P-O bonds existing in the PO4 units of phosphate glass networks. The 2 P-O distance peaks, separated by about 12 pm, which were found in the zinc and the calcium ultraphosphate glasses studied are assigned to oxygen sites on bridging (OB) and terminal (OT) positions. The mean P-O distances are nearly invariable versus the growing metal oxide content which results from an elongation of the P-OB and P-OT bonds. The bond lengths which are known from the related crystal structures and from ab initio calculations show almost the same behaviour. The discussion of further details of the crystal structures leads to the conclusion that P-OB rather than P-OT distances should show more details in case of diffraction measurements of even higher real-space resolution.
The change of the Zn-O coordination number from 6 to 4 versus increasing ZnO content, which was obtained in previous X-ray diffraction experiments, is confirmed by the recent combination of neutron and X-ray diffraction data. On the other hand, the Ca-O coordination number of about 6 is almost invariable.
Interaction of Slow Neutrons with Cobalt and Tin
Authors: Knopf K. , Waschkowski W. , Aleksejevs A. , Barkanova S. , Tambergs J. 
Published: February 2015

Abstract
Coherent neutron scattering lengths and total cross sections have been measured on samples of Co, Sn and on isotopically enriched Sn-oxides. The following data were obtained:
• the coherent scattering lengths (in fm) of the bound atoms 59Co (2.49 ± 0.02), natSn (6.22 ± 0.01) 116Sn (6.10 ± 0.01), 117Sn (6.59 ± 0.08), 118Sn (6.23 ± 0.04), 119Sn (6.28 ± 0.03), 120Sn (6.67 ± 0.04), 122Sn (5.93 ± 0.03), and 124Sn(6.15 ± 0.03);
• the thermal absorption cross sections (in b) natSn (0.569 ± 0.005), 116Sn (0.50 ± 0.03), 117Sn (0.77 ± 0.06), 118Sn (0.24 ± 0.06), 119Sn (2.19 ± 0.06), 120Sn (0.55 ± 0.06), 122Sn (0.19 ± 0.06), and 124Sn (0.43 ± 0.06).
New bound levels were evaluated for the investigated nuclei. In combination with the resonance parameters the measured scattering lengths allowed the determination of potential scattering radii R' which are of particular interest for the check of the optical model.
Quantum Deformation of the Non-Polynomial Interaction V(r) = r2 + λr2/(1 + g r2 )
Authors: Nag Nivedita , Sinha Anjana , Roychoudhury Rajkumar 
Published: February 2015

Abstract
A general scheme for studying q-deformed quasi-exactly solvable problems has been developed using the partial algebraization method. Exact solutions of the deformed non-polynomial interaction generated by the potential V (r) = r2 + λr2/( 1 + g r2) are obtained.
Rotational Tunnelling in Methyl Metal Compounds X2(CH3)4 with X = As, Sb, Bi
Authors: Kuhnen A. , Müller-Warmuth W. , Prager M. , Mündt O. , Reti M. , Becker G. 
Published: February 2015

Abstract
Rotational excitations of methyl groups attached to metal atoms of the fifth main group have been investigated in X2(CH3)4 crystals with X = As, Sb, Bi by 1H nuclear magnetic resonance (NMR) relaxation measurements and inelastic neutron scattering (INS). CH3 rotation has been found to be rather weakly hindered (activation energies between 1.7 kJ/mol and 5.8 kJ/mol) so that quantum effects are important to describe the results. Tunnel splittings between 0.1 μeV and 23 μeV have been observed. Non-equivalent methyl groups in tetramethyldistibane and tetramethyldibismuthane have been identified by both INS and NMR. A consistent description of the T1 data is possible by Haupt's equation. The rotational potentials could be derived and relations to the crystal structure have been discussed.
An ab initio Study of the C60 Particle-Hole Pair C60
12+ and C60
12-
Authors: Böhm Michael C. , Schulte Joachim , Schlögl Robert 
Published: February 2015

Abstract
The C60 ions C60
12+ and C60
12- are discussed comparatively on the basis of ab initio calculations. The basis set employed is of 3-21 G* quality. By analogy with the neutral molecule the geometry of the anion is icosahedral (Ih). Both Ih systems differ, however, in the bondlength alternation. In the neutral molecule the hexagon-hexagon bondlength exceeds the hexagon-pentagon value; vice versa in the anion. C60
12+ is of C60
12- symmetry with a strong intermixing in the length of the two types of CC bonds. Calculated geometries, total energies and net charges are adopted to evaluate differences in the electronic structure of C60
12+ and C60
12-.