bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reorientational Motion of Hydrogen Bonded Octahedral Complex Anions in Hydrazinium Hexachlorostannate(IV), (N2H5)2SnCl6, as Studied by 35Cl NQR Spin-Lattice Relaxation Measurements
Authors: Kume Yoshio , Tokoro Maki , Asaji Tetsuo , Ikeda Ryuichi , Nakamura Daiyu 
Published: February 2015

Abstract
The temperature dependences of NQR frequencies and spin-lattice relaxation times, T1Q, of 35Cl in (N2H5 ) 2SnCl6 were measured. Four NQR signals distributed in a fairly wide frequency range were observed, the lowest-frequency line exhibiting an anomalous positive temperature coefficient. The highest-frequency line showed a steep temperature dependence. These results could be interpreted by considering the intermolecular interaction between CI and - NH2 in N2H5
+ . Below ca. 250 K, T1Q of the upper three signals exhibited a gradual decrease upon heating, explainable by lattice vibrations, while a shallow T1Q minimum, ascribable to the modulation of electric quadrupole interaction, was observed at ca. 110K for the lowest-frequency signal. The reorientation of [SnCl6]2- was elucidated to be highly anisotropic, in that it reorients about one of the CI-Sn-Cl axes much more frequently than about the other two axes. The activation energies were determined to be 62 and 94 kj mol -1 for the respective reorientations.
The 35Cl NQR Temperature Dependence of Hexa- and Octachlorocyclophosphazene
Authors: Koukoulas Alexander A , Whitehead M. A. 
Published: February 2015

Abstract
The 35Cl NQR temperature dependence in (PNCl2)3 and (PNCl2)4 was measured between 77 K and 293 K. The dependence in both compounds was smoothly varying. A sudden decrease in T2* near 112 K indicated the presence of a strong broadening mechanism in (PNCl2)3. The nature of this mechanism is interpreted in terms of the Cl spin-lattice relaxation
Weak Complexes of Dinitrogen: An Approach to the 14N-Nuclear Quadrupole Coupling Constant of Free N2
Authors: Legon A. C. , Fowler P. W. 
Published: February 2015

Abstract
The 14N-nuclear quadrupole coupling constants χaa(14N<2>) and χaa(14N(1)) for the ground-states of the dimers 14N(2)
14N(1) • • • HCCH and 14N(2)
14N(1) • • • HC15N have been corrected for zero-point effects and for the electrical effects of the subunit HX to give two estimatesχ(14N) = -5.01 (13) and - 5.07 (8) MHz, respectively, for the coupling constant of the isolated 14N2 molecule
A Computer-controlled, Fully Automatic NMR/NQR Double Resonance Spectrometer
Authors: Zhenye Feng , Lücken Edwin A. C , Diolot Jacques 
Published: February 2015

Abstract
A completely automatic computer-controlled NMR/NQR double resonance spectrometer is described. It features automatic tuning of the low, variable frequency power amplifier, thus permitting untended use over long periods, with high sensitivity and signal reproducibility. The sample is transferred between the low-frequency, zero-field region and the high-field region using compressed air and the possibility of switching on a field of several tens of gauss during the transfer of the sample is also included
A Contribution to the Microwave Spectra of eis- and trans-2,3-Dimethyloxirane by Fourier Transform Spectroscopy
Authors: Hartwig Holger , Dreizler Helmut 
Published: February 2015

Abstract
Microwave Fourier transform spectroscopy was used to reinvestigate the rotational spectra of cisand trans-2,3-dimethyloxirane. The potential barriers hindering the internal rotation, internal rotation parameters, and partial rs-structures were determined.
The Rotational Spectrum of 2,2-Dimethyloxirane
Authors: Hartwig Holger , Dreizler Helmut 
Published: February 2015

Abstract
The microwave spectrum of 2,2-dimethyloxirane (isobutylene oxide) in the ground and torsionally excited states was assigned and analyzed. The potential barriers hindering the internal rotation described by V3 = 11.312(9) kJ/mol and V’1 2 = 1.059(32) kJ/mol and the angles between the axes of inertia and the internal rotation axes were determined.
Experimental Realization of Stokes Modes of the Pipe by Lorentz Excitation
Authors: Pysik A. , Heber J. 
Published: February 2015

Abstract
The complete set of the Stokes modes of the pipe was first given by Brösa and Böberg. Two of these modes for an incompressible fluid were now realized in a transparent tube and detected by a laser light cut. Their velocity fields and lifetimes were compared with the theoretical predictions, and good agreement was found. The modes were generated by Lorentz force fields of appropriate symmetry induced by an electrical current through the fluid and external magnetic fields. For higher excitation intensities effects of mode coupling could be observed
Nitrogen Nuclear Quadrupole Resonance Dips in the Proton Spin Relaxation Dispersion of Nematic and Smectic Thermotropic Liquid Crystals
Authors: Pusiol D. J. , Humpfer R. , Noack F. 
Published: February 2015

Abstract
The Larmor frequency dependence of the proton spin relaxation time, obtained by means of the fast field-cycling NMR technique, has been used to study the 14N quadrupole coupling constant K and its asymmetry parameter η in the nematic and smectic phases of some liquid crystalline azoxybenzenes (PAA, BAB, HAB, HpAB), cyanobiphenyls (8CB, 9CB, 11CB) and oxycyanobiphenyls (9 OCB). Due to fast molecular reorientations, the effective quadrupole coupling constants are relatively small, whereas surprisingly the asymmetry parameters are rather large. The temperature dependence of both K and η within the mesophases, as well as their discontinuities at the different mesophase transitions, can be interpreted by the anisotropy of molecular rotations. It is found that temperature effects are significantly more pronounced for the (biaxial) smectic-C phase of the heptyloxyazoxybenzene (HpAB) than for the (uniaxial) smectic-A phase of the various investigated cyano- and oxycyanobiphenyls. As a rule, η turned out smaller in the smectic than in the nematic state, whereas K has similar values in both phases
About the Radical Formation in the Pyrolysis of Formic Acid at High Temperatures
Authors: Klatt M. , Röhrig M. , Wagner H. Gg. 
Published: February 2015

Abstract
The formation of radicals in the HCOOH pyrolysis was investigated in the temperature and density range between 1450 and 2450 K and 2 • 10-6 and 1.2 • 10-5 mol /cm3, respectively. The small amount of radicals found indicates that a radical forming reaction path in the formic acid pyrolysis is smaller than 0.2% of the total decomposition rate
Quadrupole Hyperfine Structure in the Rotational Spectra of Sulfuryl Chloride
Authors: Merke Ilona , Dreizler Helmut 
Published: February 2015

Abstract
The nuclear quadrupole coupling of [35Cl,35Cl]- and [35Cl,37Cl]-sulfuryl chloride, SO2Cl2 was investigated using waveguide microwave Fourier transform (MWFT) spectroscopy. The analysis was performed with direct diagonalization of the Hamiltonian matrix. It was possible to determine the complete coupling tensor with high accuracy. SO2
35Cl2 : χaa ( 35Cl1) = χaa(35Cl2) = -33.049(6) MHz, χcc (35Cl1) = χcc (35Cl2) = 40.356 (9) MHz, χab (35Cl1) = - χab(35Cl2) = + 52.67 (63) MHz. SO2
35C137C1: xaa ( 35Cl)= -29.582(17) MHz, χcc(35Cl) = 40.340(25) MHz, χab(35Cl)= +52.3(14) MHz, χaa(37Cl)= -28.723(18) MHz, χcc(37Cl) = 31.822(28) MHz, χab,(37Cl) = + 37.3(19) MHz. We also determined the quadrupole coupling constants in their principal axes system. In comparison with the structure, the z-axis of the coupling tensor was found to be tilted 2.0° out off the S-Cl bond axis
Combination of EXAFS and Differential Anomalous X-ray Scattering for Studying Ni 2 Zr Amorphous Alloy
Authors: Babanov Yu. A. , Sidorenko A. F. , Shvetsov V. R. , Bionducci M. , Licheri G. , Navarra G. , Ageev A. L. , Vasin V. V. 
Published: February 2015

Abstract
In this paper we report a first application of the new idea of combining EXAFS and differential anomalous scattering techniques to obtain partial distribution functions for a binary amorphous sample. This method has been successfully employed in extracting Ni-Ni and Ni-Zr pair distribution functions for Ni2Zr prepared by mechanical alloying. A comparison with results from previous studies is also reported.
Determination of some Dye Parameters by Polarized Fluorescence Spectroscopy
Authors: Wolarz Eryk 
Published: February 2015

Abstract
A method of determining the angles between the emission and absorption dipole moments and the molecular symmetry axis is described. The order parameters <P2> and <P4> of nematic-dye mixtures are also calculated. The method is applied in investigations of tricarboxylic acid derivatives dissolved in the nematic mixture E 18 (Merck).
Short Range Structure of Amorphous Ni50Ta50-Alloys by Means of X-Ray- and Neutron-Diffraction
Authors: Uhlig H. , Rohr L. , Güntherodt H.-J. , Fischer P. , Lamparter P. , Steeb S. 
Published: February 2015

Abstract
Amorphous Ni50Ta50-samples with their high crystallization temperature of 985 K were investigated. To evaluate the three partial structure factors of amorphous Ni50Ta50 one X-ray diffraction experiment was performed with Ni50Ta50 and two neutron diffraction experiments with Co10Ni40Ta50 and with Ni50Ta50, respectively. The Bhatia-Thornton partial structure factor SCC(Q) indicates rather strong chemical short range order which also explains the premaximum observed in the Faber-Ziman partial SNiNi(Q)-function. The nearest neighbor distance is 2.82 Å for Ni-Ni, 2.91 Å for Ta-Ta, and is shortest for Ni-Ta, 2.44 Å. The coordination numbers are NNiNi = 4.9, NTaTa = 8.2, and NNiTa = 6.0. We report on the chemical short range order and the possible binding behavior in a-Ni50Ta50 and compare the present results with those reported in the literature on a-Ni40Ti60 as well as on a-Ni55Ta45
Molecular Reorientation of Methanol in Mixtures with Carbon Tetrachloride
Authors: Zeidler M. D. , Gill D. S. , Zeidler M. D. 
Published: February 2015

Abstract
Proton and oxygen-17 nmr relaxation rates of CD3
17OH as well as deuteron nmr relaxation rates of CH3OD were measured in mixtures with carbon tetrachloride at different compositions and temperatures. By varying the 170-content different contributions to the proton relaxation rate could be separated and from the 17O-H dipolar interaction contribution the correlation time τ2
OH of the OH bond was determined. Using these correlation times the composition dependence of the deuterium and oxygen-17 quadrupole coupling constants of methanol was derived. A strong variation of the coupling constants over the measured composition range is evident
Elastic Scattering of Electrons by Helium Atoms at Intermediate Energies
Authors: Chhaya V. M. , Tarwadi J. J. , Chhag Smita 
Published: February 2015

Abstract
The unitarised Eikonal Born series (UEBS) method has been used successfully by Byron et al. for elastic scattering of electrons and positrons by hydrogen atoms. Here an attempt is made to apply the UEBS method in the case of elastic scattering of electrons by helium atoms. The total and differential cross sections are calculated for the energy range 100-700 eV. The results are compared with experimental and other theoretical results. It is found that the results obtained with the UEBS method agree best with the experimental results.
Structural Phase Transitions in (n-C3H7NH3)2SbBr5
Authors: Jakubas R. , Bator G. , Foulon M. , Lefebvre J. , Matuszewski J. 
Published: February 2015

Abstract
Dielectric, DSC, thermal expansion and preliminary X-ray diffraction studies on (n-C3H7NH3)- SbBr5 are reported. It was found that this crystal undergoes a complex sequence of phase transitions. On cooling: phase I → phase II at 188.7 K (continuous), II → III at 165 K (1st order, ΔS = 26.8 J/mol K), III → IV at 137 K (1st order, 1.6 J/mol K). On heating: IV → III at 154 K, III → II’ at 168 K, II’ → II at 177 K (1st order, 2.8 J/mol K), II → I at 189 K. All 1st order phase transitions are likely due to the motion of the n-C3H7NH3
+cations. The dielectric dispersion studies between 100 Hz-1 MHz within the phases I and II indicate a fast reorientational motion of dipoles with τ < 10−7
S.
Superposition and Polarization Effects on the Electron Density of Lone Pairs
Authors: Olovsson Ivar , Ptasiewicz-Bak Halina , Mclntyre Garry J. 
Published: February 2015

Abstract
There appears to be conflicting experimental evidence on the redistribution of the electron density in the lone-pair and other regions of a molecule due to the interaction with its nearest neighbours. In some experimental as well as theoretical deformation density maps a decrease in the lone-pair density has been reported, whereas in other cases an increase has been found. It appears that two major, counteracting factors are responsible for these differences (apart from experimental errors in the diffraction studies and limited accuracy in the theoretical calculations): an increase in the lone-pair density is expected due to the polarizing influence of the neighbours, whereas simple superposition of the isolated monomer deformation densities will lead to an apparent decrease due to the overlap with the negative contours of the neighbouring atom. Depending on which of these factors is the dominant one, an increase or decrease may thus be observed.
These points are illustrated by recent results on nickel sulfate hexahydrate and some other hydrogen-bonded compounds. The electron density based on the fitted deformation functions of all atoms in the structure is compared with the individual densities calculated from deformation functions of the separate monomers. In this way the effects of simple superposition of the individual densities have been studied, and a partitioning of the electrostatic and polarization contributions to the hydrogen bonds and other relatively weak bonds to the oxygen lone-pairs attempted.
The Identification of Phonon-Phonon Interactions in Anharmonic Crystals by X-Ray Diffraction Data
Authors: Tsarkov A. G. , Tsirelson V. G. 
Published: February 2015

Abstract
The effect of anharmonic atomic vibrations on the elastic scattering of X-rays by a crystal is treated by time-independent perturbation theory. The complete expression for the anharmonic temperature factor (TF) in the high-temperature limit is presented for atoms in general positions. The phonon-phonon interactions in an anharmonic crystal may be identified with X-ray diffraction data by using various temperature and scattering vector q dependencies of different anharmonic contri-butions to the TF. The expression for the intensity of elastic scattering by an anharmonic crystal contains an additional factor -the anharmonic cross-term. This term has to be taken into account for obtaining the unbiased thermal parameters of fourth order in | q | from X-ray diffraction data.
New Opportunities for Charge Density Studies Using the FAST Area Detector
Authors: Lehmann Christian W. , Karaulov Alexander , Hursthouse Michael B. 
Published: February 2015

Abstract
The requirements for charge density studies of more complex molecules have been realized by use of the FAST area-detector diffractometer in conjunction with a rotating-anode generator, which allows to collect large quantities of diffraction data within less than two days, independent of unit cell size. Oxalic acid dihydrate has been chosen for test experiments. Data collection strategies are described and preliminary results are presented. These show that data of sufficiently high quality for charge density studies can be collected.
Use of Symmetry in Coupled Hartree-Fock Calculations of Non-linear Response Tensors in Molecules
Authors: Lazzeretti P. , Malagoli M. , Zanasi R. 
Published: February 2015

Abstract
A new computational scheme for electric dipole hyperpolarizabilities has been devised within the coupled Hartree-Fock method. Only the projection of second-order perturbed orbitals onto the subspace spanned by unperturbed virtual orbitals is computed. The entire molecular symmetry is exploited to reduce computational effort: a reduced two-electron integral file containing only symmetry-distinct matrix elements over the atomic basis functions is processed at each iteration. In addition, only symmetry-independent first-and second-order perturbed density matrices need to be calculated. An efficient computer program implementing the present approach has been developed.
Electron Density Distributions and Atomic Charges
Authors: Hess B. , Lin H. L. , Niu J. E. , Schwarz W. H. E. 
Published: February 2015

Abstract
Accurate electron densities and X-ray form factors of Li, Be, F and their ions have been calculated. Electron correlation, crystal fields and ionic charge transfer change the form factors by up to a few percent, mainly in the range of sin θ/ λ < 1/3 Â -1 . Although electron correlation and crystal fields are small perturbations, their effects on the density and form factor are not additive. Densities or form factors of atomic and ionic systems are very similar; [Li0F0] and [Li+F-] procrystals differ by an effective charge transfer of not more than 0.4 e. Charge transfer and charge overlap in crystals cannot be distinguished uniquely. When the experimental data on Li2BeF4 (approximately reproduced by 3/4 atomic plus 1/4 ionic procrystal) are interpreted from the atomic partial charges are as low as 0.1 e (Li+ 0.1
2Be+ 0.2F- 0.1
4); when interpreted from the ionic viewpoint,

the charges are much higher, namely 0.7 e. Intermediate viewpoints are also possible.
Calculation of Compton Profiles Using a Multipole Expansion of the Momentum Density
Authors: Blaas Claudia , Redinger Josef , Podloucky Raimund , Jonas  
Published: February 2015

Abstract
A practical method for the calculation of Compton profiles for cubic systems with O and Oh symmetry is presented that is based on a multipole expansion of the electron momentum density (EMD) in terms of cubic harmonics. The central quantities, the expansion coefficients, are deter-mined by a Gaussian-type integration (special directions) over the angular coordinates. From these coefficients the coefficients of an analogous expansion of the Compton profile can be directly calculated, establishing a transparent relationship between the electron momentum density and the Compton profile. This direct relationship offers the possibility of tracing back Compton-profile anisotropics to EMD anisotropics more easily, as demonstrated for MgO and FeAl.
Atomic Orbitals from Compton Profiles
Authors: Schmider Hartmut , Smith, Jr. Vedene H. 
Published: February 2015

Abstract
A recently developed method for the least-squares reconstruction of one-particle reduced density matrices from one-particle expectation values has been applied to isotropic Compton profiles of neon from the literature. The resulting densities in momentum and position space are compared with the ones obtained from ab-initio calculations.
Dynamic Structure Factor: An Introduction
Authors: Sturm K. 
Published: February 2015

Abstract
The doubly differential cross-section for weak inelastic scattering of waves or particles by manybody systems is derived in Born approximation and expressed in terms of the dynamic structure factor according to van Hove. The application of this very general scheme to scattering of neutrons, x-rays and high-energy electrons is discussed briefly. The dynamic structure factor, which is the space and time Fourier transform of the density-density correlation function, is a property of the many-body system independent of the external probe and carries information on the excitation spectrum of the system.
The relation of the electronic structure factor to the density-density response function defined in linear-response theory is shown using the fluctuation-dissipation theorem. This is important for calculations, since the response function can be calculated approximately from the independent-particle response function in self-consistent field approximations, such as the random-phase approximation or the local-density approximation of the density functional theory. Since the density-density response function also determines the dielectric function, the dynamic structure can be expressed by the dielectric function.
Momentum-Density Studies of Some Compounds with Triatomic Linear Anions
Authors: Horenian R. O. , Weyrich W. 
Published: February 2015

Abstract
High-purity powder samples of lithium and sodium azide (LiN3 , NaN3), cyanate (LiOCN, NaOCN) and hydrogen fluoride (LiFHF, NaFHF) were studied by means of 59.54 keV Compton spectroscopy. The measured isotropic Compton profiles were corrected for multiple scattering and transformed to spherically averaged reciprocal form factors Ba(s).
The experimental results are compared with theoretical reciprocal form factors obtained from Hartree-Fock calculations with different types of basis sets (Gaussian-and Slater-type orbitals, with and without polarisation functions) both for the free ions and for several kinds of clusters. The importance of intraionic and interionic interaction for the description of chemical bonding in these compounds is pointed out and discussed.
Compton Scattering from Heavier Metals
Authors: Sharma B. K 
Published: February 2015

Abstract
The use of Compton scattering in the determination of electronic structure has grown considerably in the last two decades. With the advent of synchrotron radiation it has become possible, even with good resolution, to measure several single-crystal orientations to determine three-dimensional electron momentum distributions. Although most of the earlier work has been directed to low-Z materials, in the last few years medium and high-Z metals have also been investigated with this technique. In this paper we present a review of these studies on heavier metals with particular attention to the difficulties encountered. Compton profile measurements from techniques based on energetic ion beams are also considered briefly.
Compton Scattering Experiments with Polychromatic Radiation
Authors: Schütz Wolfgang , Waldeck Beate , Flösch Dietmar , Weyrich Wolf 
Published: February 2015

Abstract
We show an iterative algorithm that allows to obtain accurate Compton profiles J(q) from Compton scattering spectra I2 (ω2), if the excitation radiation is not strictly monochromatic. It requires knowledge of the spectral distribution of the primary radiation I1(ω1), validity of the impulse approximation and dominance of a monochromatic part in I1(ω1) over the polychromatic rest. Conversely, the primary spectrum is often experimentally not directly accessible. In such a situation it is possible to evaluate the primary spectrum I1(ω1) from the spectrum of scattered photons, I2(ω2), with a similar iterative algorithm. We use a scattering target of high atomic number in order to ensure that the elastically scattered photons dominate the inelastically scattered ones. From the scattered spectrum we get a model for the Compton profile that allows us to separate the inelastic part of the scattered spectrum from the elastic part, which, in turn, is proportional to the spectral distribution of the primary radiation.