bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anomalous Temperature Dependence of Spin-lattice Relaxation Time of the 14N-NQR Line in NaNO2
Authors: Igarashi M. , Eto K. , Saito Y. , Abe Y. 
Published: February 2015

Abstract
The temperature dependence of the 14N-NQR spin-lattice relaxation time T1 of a powder sample of NaNO2 prepared from saturated aqueous solution could be fitted by a monotonic curve. When this sample was annealed, two minima of the T1 -Tcurve appeared around 35 K and 77 K. The origin of this phenomenon is discussed.
35Cl NQR Spin-Lattice Relaxation in Paramagnetic CuPtCl6 · 6H2O
Authors: Mizuno Motohiro , Asaji Tetsuo , Nakamura Daiyu , Horiuchi Keizo 
Published: February 2015

Abstract

35Cl NQR spin-lattice relaxation times T1Q of paramagnetic CuPtCl6 · 6H2O were measured as a function of temperature. Below the cooperative Jahn-Teller phase transition at Tc = 136 K, an almost temperature independent T1Q between 0.6 and 1 ms was obtained for each line of the triplet observed. This suggests that the nuclear spin-lattice relaxation of chlorine is dominantly determined by magnetic dipolar interactions between chlorine nuclei and electron spins. No marked anomaly in the nuclear relaxation rate was detected at T c . Above Tc , T1Q for the single 35Cl NQR line increased from 0.6 ms at Tc to 1-4 ms at 365 K. The rapid T 1Q decrease observed above ca. 390 K can be attributed to a reorientational motion of the [PtCl6]2- anion with an activation energy of 1.1 x 102 kJ mol-1 .
Calculation of NQR v's and T1
-1' s being proportional to T4 and T5 , respectively
Authors: Máckowiak Mariusz , Dimitropoulos Costas 
Published: February 2015

Abstract
The second-order Raman phonon process for a multilevel spin system is shown to give a quadru-polar spin-lattice relaxation rate T1
-1varying as T5 at very low temperatures. This relaxation rate for quadrupole spins is similar to the one discussed for a paramagnetic spin system having a multilevel ground state. The temperature dependence of T1 is discussed on the basis of some simplifying assumptions about the nature of the lattice vibrations in the Debye approximation. This type of relaxation process has been observed below 20 K in tetramethylammonium hydrogen bis-trichloroacetate for the 35Cl T1
-1 . Below 20 K the NQR frequency in the same crystal reveals a T4 temperature dependence due to the induced modulations of the vibrational and librational coordinates by the low-frequency acoustic phonons.
A NQR Study of γ-alumina Containing Chemisorbed Cl2
Authors: Sharma Virendra K. , Richarz Werner , Sharma Surendra , Weiss Alarich 
Published: February 2015

Abstract
Cl2 was adsorbed at 370 and 870 K on commercially available y-alumina, with BET surface area of 180m2/g, after dehydration at 850 K. NQR measurements were carried out between 55 and 6 MHz. The sample containing Cl2 chemisorbed at 870 K showed the presence of a set of quite strong NQR signals with frequencies lower than 10.6 MHz, and another set of very weak NQR signals between 18.5 and 13.0 MHz. The stronger signals have been inferred as due to Al and have been assigned to Al in three distinct environments. The values of e2 Qq/h and η determined for the signals are (1) 35.9 MHz, 0.53; (2) 35.7 MHz, 0.74; and (3) 35.3 MHz, 0.0 respectively. These values of e2 Qq/h are found to be very high as compared to those estimated for 27Al at distorted octahedral and tetrahedral sites of the alumina, viz. 3.5 and 4.0 MHz respectively, from MAS-NMR. Therefore, chemisorption causes 27Al to exist in the surface region at sites with greater distortion than in the interior of the particles but much smaller than in the case of completely dehydrated samples for which no NQR signals could be observed. The weak signals have been tentatively attributed to 35Cl. The present results demonstrate that the NQR technique can be used in studies of chemically bound species on heterogenous catalysts.
Two-dimensional Nutation Echo Nuclear Quadrupole Resonance Spectroscopy
Authors: Harbison Gerard S. , Slokenbergs Andris 
Published: February 2015

Abstract
We discuss two new two-dimensional nuclear quadrupole resonance experiments, both based on the principle of nutation spectroscopy, which can be used to determine the asymmetry parameter, and thus the full quadrupolar tensor, of spin-3/2 nuclei at zero applied magnetic field. The first experiment is a simple nutation pulse sequence in which the first time period (t1) is the duration of the radiofrequency exciting pulse; and the second (t2) is the normal free-precession of a quadrupolar nucleus at zero-field. After double Fourier-transformation, the result is a 2 D spectrum in which the first frequency dimension is the nutation spectrum for the quadrupolar nucleus at zero-field. For polycrystalline samples this sequence generates powder lineshapes; the position of the singularities, in these lineshapes can be used to determine the asymmetry parameters η in a very straightforward manner, η has previously only been obtainable using Zeeman perturbed NQR methods. The second sequence is the same nutation experiment with a spin-echo pulse added. The virtue of this refocussing pulse is that it allows acquisition of nutation spectra from samples with arbitrary inhomogeneous linewidth; thus, asymmetry parameters can be determined even where the quadrupolar resonance is wider than the bandwidth of the spectrometer. Experimental examples of 35Cl, 81Br and 63Cu nutation and nutation-echo spectra are presented.
Numerical Design of Composite Pulses for Polycrystalline Samples in Pulsed NQR Spectroscopy
Authors: Ramamoorthy A. , Narasimhan P. T. 
Published: February 2015

Abstract
The density matrix approach along with fictitious spin-1/2 or tensor operator formalisms were employed to obtain general expressions for <Ix>and thus the signal induced in a coil in the case of physically equivalent non-interacting spin I = 1 and 3/2 nuclei in a single crystal with a three-pulse composite pulse. The corresponding powder averages were then obtained and the dependence of the signal on the i-th pulse flip angle (θi) and phase (ϕi) studied. A numerical procedure established the optimum "π/2" composite pulse for polycrystalline samples as (90)0 -(70)45 -(20)25 , where the quantity in parentheses denotes the flip angle and the subscript the phase. A two-pulse composite pulse of the form (126)0 -(300)80 was also inferred, but the three-pulse composite pulse is superior. These composite pulses are shown to have general validity for other spin I values.
Modeling of High-Signal Electrostriction. II
Authors: Cieminski J von 
Published: February 2015

Abstract
The predictions obtained with a thermodynamical method are compared with experimental results. Several materials which pass a ferroelectric phase transition of first or second order are investigated. The predictions correspond well with the experimentaly determined qualitative and quantitative features as to the field and temperature dependence. Finally, extraordinary strain-field curves are predicted and proved.
Microwave Spectra of Furazan. III. Rotation Spectra of Vibrationally Excited States
Authors: Stiefvater Otto L. 
Published: February 2015

Abstract
The pure rotational spectra of molecules in 21 vibrationally excited states of the heterocyclic compound furazan (C2H2N2O) have been detected and studied by DRM microwave spectroscopy. Rotational parameters are reported for the 12 fundamental levels below 1500 cm-1 , and the contri-butions from 10 vibrational modes to the effective rotational constants and to the inertia defect of furazan are calculated.
Thallium Nuclear Magnetic Relaxation in Solid Thallium (I) Thiocyanate TlSCN: Phase Transition and Ionic Motion
Authors: Furukawa Yoshihiro , Nakamura Daiyu 
Published: February 2015

Abstract
The NMR spin-lattice relaxation time (T1) and linewidth parameter (T2*) of 203Tl and 205T1 in solid T1SCN were measured from 290 K up to the melting point (Tm = 507 K). The nonexponential magnetization recovery of could be characterized by a short (T1
s) and a long (T1
1) component. T1
1 showed a T-2 dependence below ca. 350 K in the orthorhombic phase (T<Tc = 371 K) and a minimum in the tetragonal phase (Tc<T<Tm), which were interpreted in terms of lattice vibrations and head-to-tail flips of the linear SCN- ions, respectively. A broad minimum of 77 around 360 K was explained in terms of indirect nucleus-electron scalar coupling between 203Tl and 205Tl, modulated via the anionic flips occurring in the symmetric and asymmetric potential fields for the highland low-temperature phase, respectively. The phase transition is closely related to dynamical disorder of the anionic orientations. At higher temperatures, translational self-diffusion of Tl+ was evidenced by the T2* and T1
s results
Multiphoton Ionization of Mixed Benzene-Water-Metanol Clusters. Competitive Microscopic Solvation
Authors: Börnsen K. O. , Selzle H. L. , Schlag E. W. 
Published: February 2015

Abstract
Clusters of benzene with polar molecules are observed from a supersonic jet expansion of a ternary mixture of benzene, water and methanol seeded in Helium. It is found that complex formation with methanol is strongly enhanced when a single water molecule is preadsorbed.
A Deuteron NMR Study on the Dynamics of Fluorobenzene Molecules Adsorbed o nGraphite and Boron Nitride
Authors: Boddenberg B. , Grundke V. 
Published: February 2015

Abstract
The present 2H NMR study gives some evidence that a film of fluorobenzene of about one monolayer thickness on graphite undergoes a 2D phase transition from a fluid like into a rotationally disordered solid phase at ca. 160-130 K, and subsequently a 2D solid-solid transition into an ordered phase at a temperature about 90 K. A multilayer film (Θ= 8) decomposes below about 200 K into a 3 D bulk solid phase and an adsorbed film, of presumably monolayer thickness. It is concluded that the monolayer film spreads uniformly on the available surface with flat orientation of the molecules. These detailed statements can be obtained because the combined action of the intramolecular quadrupole interaction and the extramolecular magnetic shielding type coupling allows to relate the Z-axes of coordinate frames fixed in the support and fixed in the adsorbed molecule.
Molecular Dynamics Study of an Aqueous LiF Solution
Authors: Zhu Sheng-Bai , Wilse Robinson G. 
Published: February 2015

Abstract
The structure and properties of a 1.791 molal aqueous LiF solution is investigated by performing molecular dynamics simulations using a water model with both bond flexibility and instantaneously responsive polarization. On average, each cation is in close contact with about one anion. This causes a strong overlap of the hydration shells and an almost complete breakdown of the surrounding water structure. While the lone pairs of the hydration waters in the first Li+ shell occupy preferentially tetrahedral positions, the orientational distribution of the solvent molecules around F--is quite uniform. By comparing various autocorrelation functions of water molecules in the solution and in the pure liquid, the influence of solvated ions on the translational, rotational and vibrational motions of hydration water can be studied
A Theoretical Study of Fulvene Radical Anions
Authors: Khalil Salim M. , Jarjis Hayfa M. 
Published: February 2015

Abstract
MINDO-Forces calculations have been performed, with complete optimization of geometry on fulvene and X-fulvene radical anions, where X is OH, NH2, CH3, NO,2 CN, F, dimethyl and cyclopropyl. A twisted structure with angle 5° was found for fulvene anion. All substituents are stabilizing. The stabilization effect is more pronounced in the case of NO2, and very weak in the case of CH3. It was found that the substituents CH3 and CN show amphielectronic behaviour. Geometrical parameters, heats of formation, dipole moments, electron and spin densities are reported
Photophysical and Photochemical Studies of Polycyclic Aromatic Hydrocarbons in Solutions Containing Tetrachloromethane. III. Photochemical Interaction of Excited Polycyclic Aromatic Hydrocarbons with Tetrachloromethane in Two-Component Mixtures
Authors: Wiczk Wieslaw M. , Latowski Tadeusz 
Published: February 2015

Abstract
In the photoreactions of polycyclic aromatic hydrocarbons with tetrachloromethane in binary mixtures of tetrachloromethane with cyclohexane, benzene and acetonitrile, both the quenching of the fluorescence and the photoreactions run through an intermediate stage which is an exciplex of the excited hydrocarbon with tetrachloromethane. Abnormal quantum yields of the hydrocarbon decrease are interpreted in terms of the appearance of a new reaction channel via a triplex consisting of the excited hydrocarbon, solvent and tetrachloromethane. The photoreaction is quenched by diphenylpicrylhydrazyl, thus suggesting the radical nature of the chemical transformations. A kinetic scheme is suggested for the photophysical and photochemical processes describing the observed phenomena.
Notizen: The Effect of Spin-½ Dipolar Coupling on the 2H Quadrupolar Echo
Authors: Gruwel Marco L. H. 
Published: February 2015

Abstract
The effects of dipolar coupling between a deuteron and a spin-½ nucleus on the deuterium quadrupolar echo is calculated. Due to the dipolar coupling the quadrupolar echo amplitude is shown to decay to 1/2 times its initial value for t →∞
Phase Transitions in CsSnCl3 and CsPbBr3 An NMR and NQR Study
Authors: Sharma Surendra , Weiden Norbert , Weiss Alarich 
Published: February 2015

Abstract
The phase transitions in CsSnCl3 and CsPbBr3 have been studied by X-ray powder diffraction, by 81Br-NQR and by 'H-, 119Sn-, and 113Cs-NMR. At room temperature in air CsSnCl3 forms a hydrate which can be dehydrated to the monoclinic phase II of CsSnCl3. The high temperature phase I has the Perovskite structure, as the X-ray and NMR experiments show. The three phases of CsPbBr3, known from literature, have been corroborated. The results are discussed in the framework of the group ABX3, A = alkalimetal ion, B = IV main group ion, and X = Halogen ion
Monte Carlo Simulations with an Improved Potential Function for Cu(II)-Water Including Neighbour Ligand Corrections
Authors: Rode Bernd M. , Islam Saiful M. 
Published: February 2015

Abstract
Monte Carlo simulations for a Cu2+ ion in infinitely dilute aqueous solution were performed on the basis of a simple pair potential function leading to a first-shell coordination number of 8, in contrast to experimental data. A simple method was introduced therefore, which allows the direct construction of a pair potential containing the most relevant 3-body interactions by means of a correction for the nearest neighbour ligands in the ion's first hydration shell. This procedure leads to much improved results, without significant increase in computational effort during potential construction and simulation
A Finite-Field Calculation of the Dipole Flvperpolarizability of Ammonia
Authors: Maroulis George 
Published: February 2015

Abstract
The first (ß) and second (y) electric dipole hyperpolarizabilities are calculated for the ground state of ammonia. All independent components of ßxßy and yxßyö are obtained from the energies of the molecule perturbed by a homogeneous electric field. The values of yxxxx, yxxxz, yxxzz and yzzzz are 1232, -106, 1077 and 4319 e4 a4
0Eh
-3 respectively
Localized NMR Spectroscopy with a 1.5 T Whole- Body Imager Using CODEX
Authors: Jung Wulf-Ingo , Lutz Otto , Pfeffer Markus 
Published: February 2015

Abstract
With a whole-body NMR imager working at 1.5 T localized 1H and 31P spectra were obtained using the CODEX sequence. Examples are presented: With ethanol 'H spectra the resolution, stability, and sensitivity are documented. Human in vivo investigations of the yellow bone marrow of (13 mm)3 volume elements show well resolved spectra with a good signal-to-noise ratio. An example for 31P spectroscopy is also given
Electronic and Geometrical Structure of Se5, Se6, Se7, and Se8
Authors: Becker J. , Rademann K. , Hensel F. 
Published: February 2015

Abstract
The vacuum-UV-photoelectron spectra of Se2, Se5, Se6, Se7, and Se8 have been recorded at a photon energy of h ν= 10.0 eV. The isolated molecules are examined in a supersonic molecular beam employing a new photoelectron-photoion coincidence technique. The structure of the photoelectron spectra of selenium molecules with even and odd numbers of atoms differs in a characteristic manner. While the spectra of Se6 and Se8 show one single broad band, three separated bands with different intensities are observed for Se5 and two for Se7. The spectra are compared to molecular orbital energy calculations based on theoretically supposed geometries. The comparison indicates that Se6 and Se8 have Dnd-symmetrical ring structures, whereas Se5 and Se7 are C1h-symmetrical rings
Structural Characterization of Nickel Oxide
Authors: Massarotti V. , Capsoni D. , Berbenni V. , Riccardi R. , Marini A. , Antolini E. 
Published: February 2015

Abstract
It is known from the literature that a slight distortion of the ideal cubic cell is present in the NiO structure. This work shows that such a distortion can be accurately evaluated by means of a refinement of the structural and profile parameters of X-ray powder diffraction data. Moreover, since only small amounts of products are sometimes at disposal to perform structural characterizations, it was thought useful to extend the refinement procedure to X-ray data collected on NiO samples of much lower mass (15-60 mg) than those usually utilized in X-ray diffractometric studies. The results obtained show that reliable structural parameters can be obtained from low mass samples too
I4N Quadrupole Coupling in the Rotational Spectra of 2,2,2-Trifiuoroethylamine. Isopropylamine, and Aminoethanole
Authors: Keussen Ch. , Dreizler H. 
Published: February 2015

Abstract
We utilized the high resolution of microwave Fourier transform spectroscopy to investigate the 14N-hyperfine structure of trans-2,2,2-trifluoroethylamine, CF3CH2NH2, trans-isopropylamine, CH3CHNH2CH3, and aminoethanole, HOCH2CH2NH2, and the amino deuterated isotopomers trifluoroethylamine-d2 and isopropylamine-d2. The complete coupling tensor of trifluoroethylamine could be determined. We found that the fluorine atoms have a distinct effect on the nitrogen electronic surrounding of the named molecule, presumably through a hydrogen bridge bond between two of these atoms and the amino protons. For isopropylamine and aminoethanole wrong values of the coupling constants known in the literature could be corrected
The Microwave Spectrum of15N-Difluoroacetonitrile: Electric Dipole Moment and Partial r0-Structure
Authors: Ohle Bettina , Mäder Heinrich , Guarnieri Antonio 
Published: February 2015

AbstractThe rotational spectrum of15N-difluoroacetonitrile has been investigated in the frequency range from 8 to 18 GHz. From the measured lines with J up to 20, rotational constants and quartic centrifugal distortion constants have been determined. For some lines the Stark effect has been examined, yielding the components of the electric dipole moment along the a- and c-principal axes of inertia. The obtained rotational constants were also used together with the rotational constants of the normal isotopomer to derive a partial restructure of the molecule
Ion-Solvent Interactions of Zinc(II) Salts in Water- Pyridine Mixtures
Authors: Varghese Antony V. , Kalidas C. 
Published: February 2015

Abstract
The ion-solvent interactions involving zinc(II) salts viz. iodate, fluoride and benzoate in waterpyridine mixtures have been investigated by solubility and solvent transport number measurements. The standard Gibbs transfer energies of the salts (Δ Gtº), determined from their saturation solubilities in the solvent mixtures, decrease up to xpy = 0.1 for zinc(II) iodate, but up to Xpy = 0.4 for zinc(II) benzoate, and subsequently increase with the addition of pyridine. For zinc(II) fluoride, however, a continuous increase of ΔGtº with the addition of pyridine is observed. The transfer energy of Zn2 + is negative and that of anions is positive with the former decreasing and the latter increasing continuously with the addition of pyridine. The solvent transport number of pyridine (<Δpy) is positive and passes through a maximum for all the salts in the range xpy = 0.25 to 0.55. These results indicate a heteroselective solvation of the salts with Zn2 + being preferentially solvated by pyridine and the anions by water
1 /N -Energy-Solutions to Relativistic Two-Boson Systems with an Exponential Potential
Authors: Papp E. , Micu C. 
Published: February 2015

Abstract
Closed 1/N-energy-formulae for relativistic two-boson (m1 ≠ m2) systems with a vector exponential potential have been written down to first 1/N-order. Numerical estimates and structural properties are presented
Rotational Excitations and Tunneling of Nonequivalent Methyl Groups in Tetramethylstibonium Iodide as Studied by Nuclear Magnetic Resonance and Inelastic Neutron Scattering
Authors: Burbach Günter , Weiss Alarich 
Published: February 2015

Abstract
Nuclear magnetic resonance (NMR) and inelastic neutron scattering techniques (INS) have been applied to study the rotational motions and methyl group tunneling in tetramethylstibonium iodide, [Sb(CH3)4 ] I, over er a wide temperature range. Parameters describing the [Sb(CH3)4]+ cation tumbling and the methyl group reorientation at high temperatures and quantum mechanical tunneling of the methyl groups at low temperatures were determined. The results for INS and NMR experiments at low temperatures can be explained in terms of two crystallographically inequivalent methyl groups CH3(1) and CH3(2), which were established earlier by the crystal structure determination. In the INS spectra two tunneling lines at 22.0 μeV for CH3(1) and 1.05 μeV for CH3(2) with inelastic intensities in the ratio 3:1 were observed at T = 4 K. The activation energies derived from proton NMR spin-lattice relaxation time measurements for the thermally activated methyl group rotation are 1.50 kJ/mol for CH3(1) and 3.81 kJ/mol for CH3(2). They are in accordance with the activation energies obtained from neutron fixed-window measurements. The activation energy for [Sb(CH3)4]+ cation tumbling is 50.9 kJ/mol as determined from the high temperature spin-lattice relaxation behaviour. Rotational potentials for the methyl groups are derived. For both kinds of inequivalent methyl groups the threefold potential terms dominate; three- and sixfold potential contributions are shifted by 180°
The Rotational Zeeman Effect of Imines II. Cis- and Trans-Ethanimine and Trans-Syn- and Trans-Anti-Propenimine, their g-Tensors, Magnetic Susceptibility Anisotropics, Molecular Electric Quadrupole Moments, 14N Nuclear Quadrupole Coupling Constants, and 14N Spin-Rotation Coupling Constants; a Microwave Spectroscopic Study Combined with Quantum Chemical Calculations
Authors: Krause H. , Sutter D. H. 
Published: February 2015

Abstract
The zero field 14N-hfs-multiplets and the high-field Zeeman-hfs-multiplets of low-J rotational transitions of the title compounds were observed in a flash pyrolysis setup under high-resolution conditions. From the zero-field hfs patterns the 14N spin-rotation coupling constants and the 14N nuclear quadrupole coupling constants were obtained. From the high-field Zeeman-hfs-multiplets, the diagonal elements of the molecular g-tensor and the anisotropies in the diagonal elements of the molecular magnetic susceptibility tensor were determined and were used to derive the diagonal elements of the molecular electric quadrupole moment tensor. INDO calculations and restricted Hartree-Fock self consistent field calculations with a basis of TZVP quality were carried out at the experimental structures and critically compared to the experimental results