bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal Structures and 35Cl NQR Spectra of the Metastable and the Stable Phase of Guanidinium bis-Monochloroacetate, [C(NH2)3 ]⊕[(ClH2C)COOH ••• OOC(CH2Cl)l⊖
Authors: Basaran Reha , Dou Shi-qi , Weiss Alarich
Published: February 2015

From acid aqueous solutions of guanidinium carbonate and monochloroacetic acid, (ClH2C)COOH :H2 NC( = NH)NH2 ≧ 2.5, the compound [C(NH2)3]⊕ [(ClH2C)COOH • • • OOC(CH2Cl)]⊖ crystallizes with the space group Ci
1P1̄,Z = 4, a = 1147.4 (5) pm, b= 1113.2 (5) pm, c = 876.5 (4) pm, α = 88.66 (2)°, β = 80.31 (2)°, γ = 84.41 (2)° (metastable phase I). Cooled to 77 K once, phase I transforms at room temperature slowly into the stable phase II, orthorhombic, D2h
15 - Pbca, Z = 8, a= 1299.2 (4) pm, b= 1533.7 (4) pm, c= 1073.9 (3) pm. The crystal structure determinations show for both phases an ionic lattice with guanidinium cations [C(NH2)3]⊕ and acid bis-(monochloroacetate) anions [(ClH2C)COOH • • • OOC(CH2Cl)]⊖ in which a monochloroacetic acid molecule and a monochloroacetate ion are bound to the dimer anion by an asymmetric hydrogen bond O-H • • • O.

A strong crystal field effect, much dependent on temperature, is observed in the 35Cl NQR quadruplet spectrum of phase I, with a frequency spread of ≈4 MHz at 300 K, whereas in phase II the frequency splitting of the observed 35Cl NQR doublet is almost constant between 77 K and 310 K, about 700 kHz. The phase transition I → II is very sluggish and unidirectional. The transition II → I needs the recrystallization of II from water.

Structure and dynamics of the two solid phases are discussed.
Viscosity B Coefficients of Some Tetraalkylammonium Bromides, Lithium Tetrafluoroborate and Tetrabutylammonium Tetraphenyl borate in Propylene Carbonate
Authors: Muhuri Prakash K. , Hazra Dilip K.
Published: February 2015

The viscosities of solutions of tetraalkylammonium bromides, R4NBr (R = -C2H5 to -C7H15), lithium tetrafluoroborate (LiBF4) and tetrabutylammonium tetraphenylborate (Bu4NBPh4) in propylene carbonate (PC) have been measured at 25, 35 and 45 °C. The relative viscosities have been analyzed using the Jones-Dole equation in the form of unassociated electrolytes, and the viscosity B-coefficients have been evaluated. The thermodynamic parameters have been calculated using the transition-state treatment and the measured temperature dependencies. Ionic B values have also been derived and discussed in terms of Einstein's equation. The analysis shows that Li+ is highly solvated compared to other cations and anions in this medium.
A Technique to Classify the Similarity Solutions of Nonlinear Partial (Integro-)Differential Equations. II. Full Optimal Subalgebraic Systems
Authors: Kötz H.
Published: February 2015

"Optimal systems" of similarity solutions of a given system of nonlinear partial (integro-)differential equations which admits a finite-dimensional Lie point symmetry group Gare an effective systematic means to classify these group-invariant solutions since every other such solution can be derived from the members of the optimal systems. The classification problem for the similarity solutions leads to that of "constructing" optimal subalgebraic systems for the Lie algebra Gof the known symmetry group G. The methods for determining optimal systems of s-dimensional Lie subalgebras up to the dimension r of Gvary in case of 3 ≤ s ≤ r, depending on the solvability of G. If the r-dimensional Lie algebra Gof the infinitesimal symmetries is nonsolvable, in addition to the optimal subsystems of solvable subalgebras of Gone has to determine the optimal subsystems of semisimple subalgebras of Gin order to construct the full optimal systems of s-dimensional subalgebras of Gwith 3 ≤ s ≤ r. The techniques presented for this classification process are applied to the nonsolvable Lie algebra Gof the eight-dimensional Lie point symmetry group Gadmitted by the three-dimensional Vlasov-Maxwell equations for a multi-species plasma in the non-relativistic case.
Fluorescence Anisotropies of 4-Dimethylamino-ω- diphenylphosphinyl-trans-Styrene in Isotropic Media in the Case of One-and Two-Photon Excitation
Authors: Kawski A. , Gryczyński J. , Gryczyński Z.
Published: February 2015

Fluorescence emission anisotropies, r, and mean lifetimes of 4-dimethylamino-ω-diphenylphosphinyl-trans-styrene (DDPS) were measured in n-butanol at different temperatures from 20 to 80 °C for one-and two-photon excitation. When increasing the temperature, the lifetime decreased from 32 to 12 ps, the r values, however, remained constant (0.315 and 0.445 for one-and two-photon excitation, respectively) and were found to be temperature independent. For DDPS in glycerol at - 5°C, where rotational diffusion does not occur during the excited state lifetime, the limiting emission anisotropies were r0 = 0.382 and r0 = 0.545 for one-and two-photon excitation, respectively, very little differing from the fundamental emission anisotropies rf = 2/5 and rf = 4/7. The small differences rf - r0 can be due to vibrations performed after excitation by the DDPS molecule as a result of the initial shock.
Nuclear Quadrupole Hyperfine Structure and Methyl Torsional Fine Structure in the Rotational Spectra of N,N-Dimethylformamide and N-Nitrosodimethylamine
Authors: Heineking N. , Dreizler H.
Published: February 2015

The complicated nuclear quadrupole hyperfine structure and methyl torsional fine structure in the rotational spectra of N,N-dimethylformamide and N-nitrosodimethylamine have been studied using microwave Fourier transform spectroscopy. It has been found that both molecules are rather similar in terms of their parameters of methyl group internal rotation as well as in terms of their amino nitrogen quadrupole coupling constants.
"Anomalous" Thermal Conductivity of Crystalline Alkali Halides Close to Their Melting Point
Authors: Khokhlov V. A. , Kodintseva A. O. , Filatov E. S.
Published: February 2015

The thermal conductivity of crystalline alkali halides MX (M = Li, Na, K, Rb, and Cs; X = C1, Br, and I) close to their melting point has been measured by the steady-state coaxial-cylinders method. It was found to change anomalously as the temperature varied. A minimum of the thermal conduc-tivity at a characteristic temperature depends on the ionic composition of the crystal. This effect is ascribed to the formation of cooperating defects in the melting lattice. An expression relating the thermal conductivity of the ionic crystal near the melting point to the concentration of these defects is proposed.
Isomerization of Diphenyl Polyenes.Part IV. Evidence for Two Luminescent Conformers of 1,4-Diphenyl-1,3-butadiene in Poly(vinyl alcohol) Films
Authors: Kawski A. , Kukliński B. , Kubicki A. , Piszczek G.
Published: February 2015

Investigations of the effect of the excitation light wavelength on the intensity distribution in the fluorescence band of 1,4-diphenyl-1,3-butadiene (DPB) in poly(vinyl alcohol) films (PVA) at 296 and 87 K for samples before and after heating to 423 K, and fluorescence lifetime measurements have shown that trans-trans and cis-trans conformers are responsible for the emission of fluorescence. The fluorescence properties of the DPB sample in PVA heated to 423 K were found to be similar to those of DBP in polyvinyl chloride and polyvinyl formal at 296 K.
The Thermal Diffusivity of Quasicrystalline Al72 Pd20Mn8 Alloy
Authors: Ohta H. , Tsai An-Pang , Inoue A. , Masumoto T.
Published: February 2015

A new cell has been developed for measuring the thermal diffusivity of small samples [about (5 x 2 x 0.5) mm3], using the laser flash method. The thermal diffusivities of small samples of titanium, SUS304 and Pyrex 7740 glass measured with this cell agree well with those obtained from samples of 10 mm in diameter and 0.4 mm in thickness. Then, the thermal diffusivity between 300 K and 950 K of quasicrystalline Al72Pd20 Mn8 with a single domain size of 5 mm, and that of crystalline Al60Pd25 Mn15 were measured. The thermal diffusivity of quasicrystalline Al72 Pd20 Mn8 was found to be 4 to 7 times smaller than that of crystalline Al60Pd25Mn15 .
Steady State Photolysis and Product Analysis of 4-Chloroanisole in Aqueous Solutions
Authors: Abd El-Hameed Faten S. M. , Krajnik Paul , Getoff Nikola
Published: February 2015

Aqueous solutions of 4-Chloroanisole (4ClA) of various concentrations saturated with Ar, N2O, air, and O2 were photolyzed under steady state conditions using uv-light of 228.8 and 253.7 nm. The reaction products (4-methoxyphenol, 4-chlorophenol, anisole and hydroquinone) were detected by HPLC. Mechanisms which account for these photoproducts are suggested.
Neglect of Diatomic Differential Overlap (NDDO) in Non-Empirical Quantum Chemical Orbital Theories
Authors: Koch Wolfhard
Published: February 2015

The possibility of a drastic reduction of electron repulsion and nuclear attraction integral evaluations occurring in non-empirical quantum chemical orbital methods of Hartree-Fock and configuration interaction type is discussed. Simplification schemes are proposed and examined in consideration of useful numerical applications.
Electron Density and Anharmonic Thermal Atomic Vibrations in K1_ xLixTaO3 (x=0, 0.05, 0.15) Perovskites
Authors: Zhurova E. A. , Zavodnik V. E. , Ivanov S. A. , Syrnikov P. P. , Tsirelson V. G.
Published: February 2015

The results of accurate X-ray diffraction studies of KTaO3 , K0,95Li0,05TaO3 and K0,85Li0,15TaO3 crystals are presented. Anharmonicity of the thermal motion of the oxygen atoms and deformation electron density maps are discussed.
Weak Reflections in the Laves Phase FeBe2
Authors: Margarida M. , Costa R. , de Almeida Maria José B. M. , Paixão José António
Published: February 2015

X-ray diffraction intensities from a single crystal of the Laves phase FeBe 2 were collected at room temperature. Atomic and thermal parameters as well as a scale factor were determined by least-squares refinements of high-angle data [(sin θ)/λ ≥ 0.6Â-1].

The results of Fourier inversion of the data are presented in terms of maps of the total density and followed by a discussion of the "effects" of two criteria for labelling reflection intensities as "unobserved", based on their statistical accuracy.
Electron Deformation Density at Temperatures around 20 K
Authors: Zobel Dieter , Luger Peter , Dreißig Wolfgang
Published: February 2015

A 20 K difTractometer for X-ray measurement is described. Electron density experiments at 15 K for oxalic acid and at 23 K for acetamide were carried through, leading to high-resolution experi-mental and multipole static density maps.
Entropy Maximizations on Electron Density
Authors: Collins Douglas M.
Published: February 2015

Incomplete and imperfect data characterize the problem of constructing electron density representations from experimental information. One fundamental concern is identification of the proper protocol for including new information at any stage of a density reconstruction. An axiomatic approach developed in other fields specifies entropy maximization as the desired protocol. In particular, if new data are used to modify a prior charge density distribution without adding extraneous prejudice, the new distribution must both agree with all the data, new and old, and be a function of maximum relative entropy. The functional form of relative entropy is s = - r In (r/t), where r and t respectively refer to new and prior distributions normalized to a common scale.

Entropy maximization has been used to deal with certain aspects of the phase problem of X-ray diffraction. Varying degrees of success have marked the work which may be roughly assigned to categories as direct methods, data reduction and analysis, and image enhancement. Much of the work has been expressed in probabilistic language, although image enhancement has been somewhat more physical or geometric in description. Whatever the language, entropy maximization is a specific and deterministic functional manipulation. A recent advance has been the description of an algorithm which, quite deterministically, adjusts a prior positive charge density distribution to agree exactly with a specified subset of structure-factor moduli by a constrained entropy maximization.

Entropy on an N-representable one-particle density matrix is well defined. The entropy is the expected form, and it is a simple function of the one-matrix eigenvalues which all must be non-negative. Relationships between the entropy functional and certain properties of a one-matrix are discussed, as well as a conjecture concerning the physical interpretation of entropy. Throughout this work reference is made to informational entropy, not the entropy of thermodynamics.
Preliminary Results of a 20 K X-Ray Study of Citrinin
Authors: Destro R. , Merati F.
Published: February 2015

A total of about 37 000 diffracted intensities has been measured at 20 K for a spherical single crystal of citrinin. Using a multipole formalism to interpret the X-ray data, maps of the charge density and of its Laplacian, as well as for the electrostatic potential have been derived. A value of 7(2) D has been obtained for the magnitude of the molecular dipole moment. A study of the electric field gradient (EFG) at the nuclei has yielded the atomic quadrupole coupling constants (QCC) and asymmetry parameters (η). A topological analysis of the charge density has been performed to characterize the intramolecular covalent and hydrogen bonds.
Experimental and Theoretical Spin Densities in Two Alkyl Nitroxides
Authors: Bordeaux D. , Boucherleb J. X. , Delley B. , Gillon B. , Ressouehe E. , Schweizer J.
Published: February 2015

The spin density in the two alkyl nitroxide compounds 4-oxo-and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (tempone and tempol) has been determined by polarised-neutron diffraction and compared to theoretical predictions obtained in both the Unrestricted Hartree-Fock and the Local Spin Density approaches.
Spin Densities in Copper-Nitronyl Nitroxide Complexes
Authors: Boucherle J.-X. , Ressouche E. , Schweizer J. , Gillon B. , Rey P.
Published: February 2015

The spin density in two copper-nitronyl nitroxide complexes, viz. bis(hexafluoroacetylacetonato)-(2,4,4,5,5-pentamethyl-l-oxy-imidazoline 3-oxide)-copper(II) and dichloro-bis(2-phenyl-4,4,5,5-tetra-methyl-l-oxy-imidazoline 3-oxide)-copper(II), has been determined by polarised-neutron diffrac-tion. Spin populations and unpaired electron wave functions have been refined.
Modern Band Theory of Disordered Alloys: Basic Concepts Including a Discussion of Momentum Densities
Authors: Bansil A.
Published: February 2015

An overview of some of the basic concepts in the modern first-principles band theory of disordered alloys is given. The question of how the notion of Bloch energy bands and Fermi surfaces generalizes to the case of the disordered system, insofar as the average electronic spectrum is concerned, is stressed. The theory is illustrated with examples chosen from the work on binary alloys; a few examples of the very recent studies of disordered phases of the high-Tc superconductors are also included. The application of the alloy theory to obtain electron and electron-positron momentum densities involved in the analysis of Compton scattering and positron annihilation (angular correlation) experiments in alloys is discussed, with a selection of relevant theoretical and experimental studies.
Electron Densities, Momentum Densities, and Density Matrices
Authors: Harriman John E.
Published: February 2015

Relationships among electron coordinate-space and momentum densities and the one-electron charge density matrix or Wigner function are examined. A knowledge of either or both densities places constraints on possible density matrices. Questions are approached in the context of a finite-basis-set model problem in which density matrices are elements in a Euclidean vector space of Hermitian operators or matrices, and densities are elements of other vector spaces. The maps (called "collapse") of the operator space to the density spaces define a decomposition of the operator space into orthogonal subspaces. The component of a density matrix in a given subspace is determined by one density, both densities, or neither. Linear dependencies among products of basis functions play a fundamental role. Algorithms are discussed for finding the subspaces and constructing an orthonormal set of functions spanning the same space as a linearly dependent set. Examples are presented and additional investigations suggested.
Compton Profiles for Atoms and Molecules: Compton Defects
Authors: Gasser F. , Roeth M.
Published: February 2015

A series expansion applied to the Born propagator present in the differential cross-section allows one to obtain successive corrections to the impulse approximation. The first and second corrections explain the essential features of the Compton defects. Results for the second corrective term are presented for 1 s, 2 s, 2 px,y, and 2 pz hydrogenic states. The decrease or increase of the scattered intensity near the maximum of the Compton profile is shown to be strongly related to geometric properties of the concerned orbital
Bremsstrahlung Contribution in Compton Scattering from Heavy Metals
Authors: Mittal Usha , Sharma B. K. , Kothari R. K.
Published: February 2015

Theoretical estimates of the spectral distribution and total intensity of the bremsstrahlung (BS) relative to the Compton yield have been determined for photoelectrons liberated in scattering experiments on heavy metals with 60 keV radiation. Whereas the total-intensity calculations are based on the approach of Alexandropoulos et al., the spectral distribution has been computed using the Born approximation along with the Elwert and form factor corrections. These results are compared with another calculation based on the approach of Lee et al. Typical results for Mo, Ta, and W are presented. It is found that the relative contribution of BS from a W target is not trivially small, although K-shell photo-ionisation is not possible at these energies.
Local Order Refinement in Liquid Lithium Niobate Using a Two Radiation Method (X-Rays and Neutrons)
Authors: Andonov P. , Chieux P. , Kimura S. , Waseda Y.
Published: February 2015

In the molten LiNbO3 , the local order of the first neighbouring atoms has been described using the total structure factors S(Q) (x) and S(Q)(n) and the total pair correlation functions G(r) (x) and G(r)(n) obtained by X-ray and neutron scattering, respectively. We have also compared the differences [RDF(r)(x) - RDF(r)(n)] of the radial distributions obtained from experiments and computed from the distances in the LiNbO3 crystal. With this refinement it was possible to extract the first pair distances r 1,Nb-o r1, Li-O an r1,O-O whit the high accuracy Δr/r ≈ 0.5%. These values are identical with those in the crystal. Fitting the RDF curves by Gaussian components centred around these distances, the first coordination numbers n 1,Nb-o n1, Li-O and n1,O-O , have been determined with an accuracy Δn/n ≈ 2%. Octahedrally coordinated niobium atoms are present in the melt in the studied range from 1623 K to 1490 K. From these results it is inferred that aggregates built from corner-sharing octahedra, tightened by lithium atoms, are present in the melt.
The Rotational Zeeman Effect of Carbonylselenide, OCSe, its Molecular Electric Quadrupole Moment, and the Effects of the C = Se Stretching and the Bending Vibration; A High Resolution Microwave Fourier Transform Study
Authors: Klesing Armin , Sutter Dieter H.
Published: February 2015

The results of a high resolution microwave Fourier transform study of the rotational Zeeman effect in the J' = 2￫J" = l transitions of 16O12C80Se, 16O12C78Se, and 16O12C77 Se are reported. From the observed g-values and susceptibility anisotropies, experimental values were derived for the molecular electric quadrupole moment, for the anisotropy in the second moments of the electronic charge distribution, for the paramagnetic susceptibility perpendicular to the OCSe chain, and for the sign of the electric dipole moment. From the Zeeman data observed for the /-type doublet, the paramagnetic susceptibility parallel to the OCSe-axis, which by symmetry is zero for the linear configuration, could be derived as a function of the bending angle, ß. Ab initio calculations of the molecular electric quadrupole moment were carried out. Fair agreement with the experimental value was obtained at the CID/LANLIDZ + pol level of computation.

The Lorentz-Stark effect, which usually leads to perturbations in the Zeeman patterns of /-type doublet lines, vanishes if data collection starts with a delay 2 μs after the end of the exciting pulses. This finding is attributed to the short collisional lifetime of fast molecules and suggests new experiments in the field of rotational relaxation studies.
Correlation between the Radiation Induced Colours and the OH-stretching Vibrations of Amazonite
Authors: Banerjee A.
Published: February 2015

The changes of colour and the OH-stretching vibrations of amazonites (K-Feldspar) on irradiation have been investigated. It is concluded that the changes are caused by radiation induced crystal defects.
The Rotational Spectrum of 2,2-Dimethylthiirane
Authors: Hartwig H. , Dreizler H.
Published: February 2015

The rotational spectrum of 2,2-dimethylthiirane (isobutylene sulfide) has been assigned for the ground and torsionally excited states. The rotational and centrifugal distortion constants, as well as the potential parameters V3 and V´1 2 are determined. The ground state spectra of the 13C and 34S isotopomers were assigned in natural abundance and heavy atom structure parameters are given.
F(α) Spectrum of Pruned Baker's Map
Authors: Jenkins Paul , Daly Mark V. , Heffernan Daniel M.
Published: February 2015

We study in detail the evolution of fractal structure within a two dimensional hyperbolic baker's map with a complete set of unstable orbits. The evolution of fractal structure within the phase space of the map is related to changes in an associated Cantor set, and this evolution is studied via their corresponding /(a) spectra. Numerical calculations of unstable periodic orbits for a related baker's map, with an incomplete set of unstable orbits, is investigated and directly related to, and characterized by, a pruned Cantor set. The effect of the pruning on the associated /(a) spectrum of the baker's map is analyzed.
Ultra small Angle Neutron Scattering from Amorphous Ni-Pd-P-Alloys
Authors: Hagenmayer R. M. , Zeyen C. M. E. , Lamparter P. , Steeb S.
Published: February 2015

Using a neutron double crystal spectrometer, thin amorphous Ni-Pd-P-samples were investi-gated at very small Q-values (10-5 Å -1 ≦Q≦10 -3 Å -1). The immersion method shows that the small angle scattering effect is mainly caused by surface scattering.
Kinetics of the Reaction HOCO + O2 in the Gas Phase
Authors: Nolte J. , Grußdorf J. , Temps F. , Wagner H. Gg.
Published: February 2015

Using the discharge flow method, the kinetics of the gas phase reaction

HOCO + O2 products (1)

was investigated at room temperature and pressures around p ≈ 2.0 mbar with Far Infrared Laser
Magnetic Resonance (FIR-LMR) detection of HOCO, HO2 , and OH. From the measured concentration-
versus-time decay profiles of HOCO in the absence and presence of a large excess of O2 , the
overall rate constant of the reaction was found to be

k1 (296 K) = (9.9 ±1.5) • 1011 cm3/mol • s.

The main reaction channel, which leads to production of HO2 + CO2 , could be established.
Structure of the Molten NaCl-MgCl2
Authors: Takagi Ryuzo , Tomita Masato
Published: February 2015

With potential parameters adjusted to reproduce the experimental structure factor of molten MgCl2 reasonably, molecular dynamics simulations of the molten NaCl-MgCl2 were carried out. The structure of this system was investigated by comparison of experimental with computational results.
Long Lived ZEKE states above the Ionization Threshold
Authors: Scherzer W.G. , Selzle H.L. , Schlag E.W.
Published: February 2015

Experiments on threshold photoionization of benzene are performed which show very long lived neutral molecular states above the ionization threshold. These states are shown to have lifetimes of tens of microseconds and longer in the energy range of vibrational excitation of the molecular core as well as for electronic excitation in the range of 5 eV above the ionization potential (IP).
Hilbert Space Methods in Hydrodynamics with Applications to Couette Flow
Authors: Knorr Georg , Ströhmer Gerhard
Published: February 2015

A new base for three-dimensional divergence-free vector fields in Hilbert space (Galerkin method) is proposed. The base fields have vanishing boundary conditions for their curl and are useful to solve the incompressible Navier-Stokes equation. The base vector potentials are obtained as the eigensolutions of the squared Laplace operator. We first derive the operator in a simply connected domain and then study Couette flow in the small gap approximation. The method yields a rapidly converging critical Taylor number and in lowest approximation a three mode model for the Taylor vortices, similar to the Lorenz model. It represents the first bifurcation of the flow very well.
On Rayleigh’s Stability Criterion for Couette Flow
Authors: Lortz D.
Published: February 2015

The stability problem of a stationary circular flow of an ideal fluid between two coaxial cylinders is considered. It is shown that Rayleigh's circulation criterion is necessary and sufficient for the total kinetic energy of an axisymmetric disturbance to be bounded in time.
Notizen: Investigation of BDH Zinc for Hydrogen Isotope Analysis by Mass Spectrometry
Authors: Tanweer A.
Published: February 2015

Using metallic zinc from BDH Chemicals, the conversion of water into hydrogen was investigated by measuring the D/H ratio of the latter. It was found that 8 μl of water, 3.0 g of zinc, and a reaction time of 30 minutes at 480 °C are the optimal conditions for the conversion reaction.
Notizen: Investigation of the Crystallinity of the Modifications of Silica by their IR-Reflectance Spectra
Authors: Banerjee A.
Published: February 2015

Infrared reflectance spectroscopy has been used for the identification of the different modifications of silica and for the determination of their crystallinity.
Proton NMR Relaxation Study of Molecular Motions in a Liquid Crystal with a Strong Polar Terminal Group
Authors: Sebastião P. J. , Ribeiro A. C. , Nguyen H. T. , Noack F.
Published: February 2015

Liquid crystalline compounds containing a cyano terminal group often exhibit peculiar molecular organizations of their mesophases. In this work we present proton NMR relaxation studies, performed by means of standard NMR and fast field-cycling NMR techniques, in the nematic (N) and bilayered smectic-A phase (SA2) of 4-pentyl-phenyl 4'-cyanobenzoyloxy-benzoate. The field-cycling measurements were used to clarify the relaxation behaviour in the low Larmor frequency range, where conventional techniques are not applicable.

Self-diffusion and rotational reorientations are found to be the essential relaxation mechanisms at MHz frequencies in the smectic mesophase, while the contribution of collective modes appears only at lower frequencies in the kHz range. In the nematic mesophase the order director fluctuations mechanism dominates the relaxation dispersion up to 10 MHz, where the rotational reorientations become important, with minor corrections from the self-diffusion process. The agreement between the experimental findings and model fits could be improved by an additional relaxation mechanism in the kHz regime, ascribed to the interaction between protons and fast relaxing quadrupolar nitrogen 14N nuclei. Though all four processes are present in the nematic and smectic-A2 phases, the overall T1 frequency dependence is quite different in the two cases. This behaviour is discussed in terms of available theoretical calculations of the proton relaxation dispersion in liquid crystals, and it is also compared with data known from other cyano compounds.
Two-Parameter Scaling of Inverse Compressibility and Its Relation to Atome and Electron Concentrations of Main-Group Solid Elements
Authors: Cho Seung-Am , Santana Maria G.
Published: February 2015

The scaling of the inverse compressibility (bulk modulus B) of the main-group solids with their valence Z and atomic volume Va revealed the validity of a simple two-parameter function B = bf(Z, Va. regardless of the type of bond and lattice structure of the solid, with a unique constant b = 3.0 x 10-19 joules per electron.
On Polynomial Gaussian Least-Squares Fits and Interpretation of the Resulting Fit-Parameters
Authors: Hohm Uwe
Published: February 2015

Fitting of experimental data with a polynomial determined by Gaussian least-squares analysis is a common and well-established praxis. However, there seems to be a lack in consistency if the resulting fit parameters are to be interpreted as physically meaningful quantities. Therefore, a detailed investigation of the fitting procedure itself as well as of the measuring process, including possible improvements of the resulting fit-parameters are presented in this paper.
The General Solutions of the Robertson-Walker Null-geodesic and their Implications
Authors: Prokhovnik S. J.
Published: February 2015

The Robertson-Walker metric gives mathematical expression to three widely-held assumptions about the nature of the observable universe. It is shown that the null-geodesic of this metric has little-known solutions for the speed and distance of a light-signal relative to its source. Some implications of these results are considered, the most interesting of these being that only in a universe whose 3-space is Euclidean (k = 0) will the behaviour of light on the cosmological scale be compatible with .our understanding of light behaviour on the local scale. It is shown in an Appendix that the derived implications of the metric are entirely consistent with Special Relativity, its underlying principles and its consequences.
Effects of Finite Larmor Radius and Hall Currents on Thermosolutal Instability of a Partially Ionized Plasma in Porous Medium
Authors: Prakash Kirti , Manchanda Seema
Published: February 2015

The effects of finite ion Larmor radius (FLR), collisions and Hall currents on thermosolutal instability of a partially ionized plasma in porous medium in the presence of uniform vertical magnetic field are investigated. It is found that the presence of each magnetic field, FLR, Hall currents and collisions, introduces oscillatory modes which were, otherwise, non-existent. In the case of stationary convection, finite Larmor radius, Hall currents, medium permeability and magnetic field may have stabilizing or destabilizing effects, but for a certain wave number range, FLR, magnetic field and Hall currents have a complete stabilizing effect. The stable solute gradient always has stabilizing effect on the system whereas the collisional effects disappear for the case of stationary convection.
A Molecular Beam Fourier Transform Microwave Spectrometer in the Range 26.5 to 40 GHz. Tests of Performance and Analysis of the D-and 14N-Hyperfine Structure of Methylcyanide-d1
Authors: Merke I. , . Dreizler H.
Published: February 2015

We present the set-up of a molecular beam Fourier transform microwave spectrometer in the range from 26.6 to 40 GHz. As a test we investigated the deuterium hyperfine structure of deutero-acetonitrile, DCH2CN. It is also shown, that the spectrometer can be used to measure highly resolved rotational spectra of van der Waals complexes.
Internal Rotation Analysis of the Ground State Microwave Spectrum of 2-Iodopropene
Authors: Gripp Joachim , Dreizier Helmut
Published: February 2015

The ground state microwave spectrum of 2-iodopropene has been reinvestigated using Fourier transform microwave spectroscopy. The barrier hindering methyl internal rotation could be ob­ tained from narrow splittings of high-J lines. In addition an improved hyperfme structure and centrifugal distortion analysis resulted in refined constants and an approximate determination of the iodine spin-rotation coupling parameters.
Dielectric Properties of 1-Hexanol in Mesitylene Solution on Admixture of Aromatic Dihydric Alcohols
Authors: Turky G. , Hanna F. F. , Klages G. , Ghoneim A. , Stockhausen M.
Published: February 2015

Broadband dielectric relaxation spectra (at 20 to 40 °C) are reported for three liquid alcohol/non­ polar solvent systems: Binary hexanol/mesitylene mixtures and two corresponding ternary mixtures, where 5 percent of hexanol are replaced by a dihydric alcohol, namely resorcinol (1,3-dihydroxyben­ zene) or 2,2´-dihydroxydiphenyl. The concentration of the polar substance(s) ranges from dilute solutions to pure alcohol(s). The lower frequency relaxation contribution, which generally is the more dominating the higher the alcohol concentration, is additionally enhanced by the diol admixture in the case of low and moderate concentrations. This can be understood as a hetero-association effect, the diol molecules playing a bridging role, which also leads to an increase in the mean lifetime of associated states.
Spatial Electron Density Distribution of Chlorine Atoms in Molecules of the Series 4-XC6H4MCCl2C(O)C6H5 (M = S and Se)
Authors: Feshin Valentin P. , Sapozhnikov Yurii E. , Shchepin Vasilii V. , Petukhova Irina Yu. , Gordeev Arsenii D. , Soifer Gennadii B.
Published: February 2015

The 35Cl NQR frequencies and EFG asymmetry parameters at the 35Cl nuclei have been mea­sured for compounds of the series 4-XC6H4MCCl2C(O)C6H5 (M = S and Se, X = H and CH3) at 77 K. The electron distribution at the Cl atoms in all the compounds studied differs from axial symmetry, and is unequal for the two Cl atoms of the CCl2 group. The results of the measurements imply pσ-electron density nonequivalence of Cl atoms in the CCl2 group of these molecules.
On the Relation between Statistics of Scalar and Velocity Fluctuations in Developed Turbulence
Authors: Peinke J. , Castaing B.
Published: February 2015

For a developed turbulence it is shown how the statistics of a passive scalar, namely the prob­ability density function of the temperature, can be related to the velocity intermittency. The results are compared with recent experimental findings on a grid-generated turbulence.
Time-Averaged Quantity of a Low-Temperature Semiconductor Experiment Reflects Scaling Behavior of Saddle-Node Bifurcation to Chaos
Authors: Richter R. , Kittel A. , Paris J.
Published: February 2015

Low-temperature impact ionization breakdown in p-type germanium crystals gives rise to spontaneous oscillations of the current flow. We demonstrate experimental evidence of a particularly high-conducting dynamical state that is limited to a finite parameter regime of the current versus magnetic field characteristic. After bifurcation from a coexisting nonoscillatory state to periodicity, one observes a type-I intermittent transition to chaos and, eventually, a jump back to the nonoscil­latory branch upon increasing the magnetic field control parameter. The scaling behavior of the underlying saddle-node bifurcation, already found in time-resolved measurements, also becomes visible in a square-root dependence of the time-averaged current developing both prior to and after the critical point. Our result might be of interest for time-averaged information is accessible.
Dispersion Potentials between Atoms and Dielectric Bodies
Authors: Schuller F.
Published: February 2015

We derive a formula for the van der Waals interaction between an atom and a dielectric surface for both ground and excited state potentials. We compare our result with previously derived expressions involving the dielectric constant at purely imaginary frequencies. We also study the relationship between atom-dielectric and ordinary atom-atom van der Waals interaction.
Crystal Structure and Phase Transitions of [C(NH2)3]3l3Sb2Cl9· 0.9 H2O
Authors: Zaleski Jacek , Pietraszko Adam
Published: February 2015

The room temperature structure of [C(NH2)3]3Sb2Cl9 · 0.9 H2O (GNCA) was solved. It crystal­ lizes in the monoclinic C2/c space group with a = 15.275, b = 8.794, c = 17.904 (in Å), β = 96.40°, V = 2390 Å3, Z = 4. Refinement of the atomic parameters by a least squares methods gave R = 0.042, wR = 0.039 for 1958 reflections with F>4σ(F). The structure consists of polyanionic (Sb2Cl9
3-)n layers built of deformed corner connected SbX6
3-octahedra. Two crystallographically inequivalent guanidinium cations are present, one situated between polyanionic layers, the other one together with a disordered water molecule inside cavities formed by polyanions. Temperature X-ray scattering experiments together with DSC studies were carried out above room temperature. Temperature dependence of the lattice parameters between 300 K and 380 K was determined and a phase transition of mixed order at 364 K was revealed.
Determination of the Sign of Nuclear Quadrupole Interaction by Laser-Radiofrequency Double-Resonance Determination of the Sign of Nuclear Quadrupole Interaction by Laser-Radiofrequency Double-Resonance
Authors: Blasberg Tilo , Suter Dieter
Published: February 2015

We describe a new type of laser-radiofrequency double-resonance experiment, which allows to determine not only the absolute value but also the sign of nuclear quadrupole coupling constants. This determination of the sign, which is essential for the comparison with calculated EFG tensors, is not possible with purely magnetic experiments. The m ethod has a high resolution and, because of the optical detection, also a high sensitivity. As an example, the quadrupole coupling constant for Pr3+ :YAlO3 was measured at 4.38 K and was found to be negative.
Wideline 2H -NMR Spectroscopy and Imaging of Solids
Authors: Blümich B.
Published: February 2015

Recent developments, focussing on reduction of the rf excitation power by stochastic excitation, on improvements in sensitivity and excitation bandwidth by magic angle spinning, and on combining wideline spectroscopy with spatial resolution for investigations o f spatially inhomogeneous objects are reviewed.
On the Reconstruction of NQR Nutation Spectra in Solids with Powder Geometry
Authors: Robert H. , Pusiol D. , Rommel E. , Kimmich R.
Published: February 2015

In single crystals the NQR nutation frequency depends on the relative orientation of the coil and the quadrupole axes. In powders the nutation lineshape is a superposition of spectra from the randomly oriented single crystals, so that powder patterns appear in such experiments if the recon­struction is performed by the Fourier transform method. In this paper an alternative reconstruction method of nutation spectra is suggested making use of the Hankel Transform. In this way the nutation spectra are simplified. Singularities arising with experiments for the determination of the asymmetry parameter η can easily be resolved. In the particular case of an axially symmetric quadrupolar tensor and a homogeneous radiofrequency field one can reduce the powder pattern to a single line without heterogeneous broadening with respect to orientation. Further improvement o f the nutation spectra can be achieved by taking advantage of the maximum entropy method, which strongly reduces apodisation and noise problems. Applications of the new data manipulation techniques to N Q R imaging methods published elsewhere and 2D zero-field N Q R spectroscopy are reported.
Investigation of Intrinsic Point Defects in Metals by Nuclear Quadrupole Double Resonance
Authors: Notter M. , Konzelmann K. , Majer G. , Seeger A.
Published: February 2015

The paper reviews the principal features of the Nuclear Quadrupole Double Resonance (NQDOR ) technique, with particular emphasis on its application to the investigation of imperfections in cubic metals. NQDOR permits measurements of the electric field gradients (EFG) at quadrupole-moment-carrying nuclei in the neighbourhood of point defects and thus to obtain “fingerprints” of these defects. An NQDOR facility set-up at the M ax-Planck-Institut für Metallforschung in Stuttgart is described. It has been used to study the intrinsic defects introduced into Cu and dilute Cu/Be alloys by low-temperature irradiation with electrons or protons or by cold-work. It is shown that all well-resolved irradiation-induced EFG observed in the present work are due to one kind of defect only, which is identified as the <100> dumbbell self-interstitial. When considered together with measurements of the electrical resistivity on the same specimens, the annealing behaviour of the NQDOR lines supports the so-called two-interstitial model of radiation damage in face-centred cubic metals rather than the one-interstitial model.
A New Pulsed Nuclear Quadrupole Resonance Spectrometer
Authors: Petersen G. L. , Bray P. J. , Marino R. A.
Published: February 2015

A new pulsed nuclear quadrupole resonance spectrometer is described and a number of Nitrogen-14 spectra are shown and discussed. The spectrometer is computer interfaced and both data acquisition and all adjustments other than the matching network tuning are automatic. Spectra may be produced using fast Fourier transforms or by the Clark Method. The latter is particularly valuable when very wide line widths are encountered.
The Breathing Mode of BaBiO3: Electric Field Gradient and Total Energy Calculations
Authors: Blaha P. , Schwarz K. , Dufek P. , Vielsack G. , Weber W.
Published: February 2015

We present ab initio full-potential linearized augmented plane wave (LAPW) band structure calculations for BaBiO3. We focus on total energies and electric field gradients at the oxygen site and present results for the breathing mode in the experimentally observed cubic and monoclinic structures of doped and undoped Ba1-xKxBiO3.
Halogen NQR and Crystal Structure of Ammonium Halides (R-NH3)+X- and (X–) (+H3NR´­NH3
+) (X–). R = (HOCH2)3C, R´ = CH2C(CH3)2CH2; X = I,Br
Authors: Dou Shi-qi , Fuess Hartmut , Paulus Helmut , Weiss Alarich
Published: February 2015

The 127I-NQR of(HOCH2)3CNH3
+ I- was determined in the range 77 ≤ T/K ≤ 310. At T = 310 K the NQR signal fades out (Tm = 463 K). The 127I spectrum ( T =77 K.): v1 =29.195 MHz, v2 = 14.597 MHz, η(121l)=0, e QΦzz h-1 (127I) = 97.315 MHz, is in agreement with the crystal structure.

The 127I NQR spectrum of 1,3-diammonium-2,2-dimethylpropane diiodide, (H3NCH2C(CH3)2CH2NH3)2+ ·2I- , is a quartet within the whole temperature range investigated, and the lines correspond to two crystallographically independent iodines: Space group P21/c, Z = 4, a = 731.2(3) pm, b = 689.0(3) pm, c = 2255.1(8) pm, β = 104.90(1)°. At 7 = 7 7 K the 127I NQR quartet is (MHz): v1 = 34.145, v2 = 32.805, v3 = 22.113, v4 = 16.787; at 295 K (same order, MHz): 30.559, 29.729, 19.810, 15.651. There are two combinations of the NQR frequencies. Considering the coordination of I-, the hydrogen bonds N -H ··· I, eQΦzzQ h-1 and η, we choose for I(1) v1 and v3, for I(2) v2 and v4. At 77 K eQΦzzQ h-1 (I(1))= 118.86 MHz,η (127I(1)) = 0.498, eQΦzzQ h-1 (I(2)) = 109.75 MHz, η(127I(2)) = 0.135 follow for the two iodine atoms. Both, eQΦzzQ h-1 (I(1)) and e eΦzzQ h-1(I(2)) decrease smoothly with increasing T: η I(2)) increases with increasing T whereas η(127I(1)) is almost constant within 77 ≤ T /K ≤ 4 0 6 .

The 79,81Br NQR spectrum of l,3-diamino-2,2-dimethylpropane dihydrobromide is also a quartet, showing two crystallographic inequivalent Br atoms in the unit cell. The frequencies are (T =273 K, MHz): v1 (79Br)= 14.303, v2 (79Br)= 12.884, (81Br)= 11.951, v2(81Br) = 10.781; space group C2/c, Z = 8 , a = 2136.4(6) pm, b = 854.6(3) pm, c = 1125.8(3) pm, β = 93.23(1)°.

Crystal structures and NQR results are discussed.
Structure and Bonding of Bromoantimonate (III) Complexes with Unusual Valency by Means of NQR and Powder X-Ray Diffraction
Authors: Okuda Tsutomu , Kinoshita Yoshihiro , Terao Hiromitsu , Yamada Koji
Published: February 2015

NQR and powder X-ray diffraction were observed for several bromoantimonate (III) complexes which contain CnH2n+1NH3 (n = 1 -3) or (CnH2n+1)2NH2(n = 1 -4) as a cation. The bond character, anion structure, crystal structure, and phase transition are discussed on the basis of the three-center-four-electron bond. A good correlation was found between the halogen NQR frequency and the Sb-X bond length.
81Br NQR and Crystal Structure of Ethylammonium Tribromomercurate(II), CH3CH2NH3HgBr3
Authors: Terao Hiromitsu , Okuda Tsutomu , Koto Kichiro , Dou Shi-qi , Weiss Alarich
Published: February 2015

The 81Br NQR triplet spectrum of (CH3CH2NH)3
⊕(HgBr3)⊖ was measured in the range 77 K to near the m.p. (99~106°C) v1 decreases strongly with increasing temperature, exhibiting 136.784 MHz at 77 K and 128.129 MHz at 298 K. v2 decreases from 82.060 MHz at 77 K to 76.322 MHz at 298 K. v3 increases with temperature, showing v3 = 81.292 MHz at 77 K and 84.903 MHz at 298 K. Replacement of the ammonium hydrogens by deuterium produces a negative shift of v1 and positive ones of v2 and v3 at high temperatures. These shifts change with temperature from |~ 0| up to |~ 200| kHz.

The crystal structure of the title compound was determined at room temperature: P 21/m, Z = 2, a = 1021.6(8) pm, b = 643.0(6) pm, c = 691.8(6) pm, β = 96.96 (4)°. The coordination of the mercury atom by the bromines is trigonal bipyramidal; by formation of bridges Hg··· Br··· Hg by one of the three bromines (Br(2)) of the planar HgBr⊖ ions a double chain of trigonal bipyramids is formed, running along the b-axis of the crystal. Br(1) and Br(3) are single bonded to Hg. The hydrogen bonds N -H···Br(1) and N -H ··· Br(3) (twice), connect the Hg-Br chains to planes lying parallel to the be plane at x = 0. The relations between the Br-NQR spectrum and the structure are discussed.
The Zeeman Effect in Quadrupole Double Resonance Spectra: Dependence of the Line Shapes on the Orientation of the Electric Field Gradient Tensor
Authors: Stephenson David , Smith John A. S.
Published: February 2015

The solid effect spectrum of 1,4-dichlorobenzene was recorded at magnetic field strengths in excess of 50 G; at these field strengths Zeeman structure is seen on the 35Cl resonance. Unlike in single resonance experiments, peaks are asymmetric, and the high frequency and low frequency solid effect peaks have not the same shape. Computer calculation o f the solid effect spectrum gives peaks which show the same asymmetry as the experimental spectrum. The simulated line shapes are found to depend on the direction the principal components of the electric field gradient in the crystal framework and indicate that qyy lies in the plane o f the benzene ring.
Internal Magnetic Field at Ba Site in Antiferromagnetic YBa2Cu3O6 Determined by 137Ba NQR
Authors: Roos J. , Mali M. , Brinkmann D.
Published: February 2015

By measuring the beat frequency of the spin-echo amplitude modulation of pulsed 137Ba NQR , the internal magnetic field of 14.8 mT perpendicular to the tetragonal c-axis at the Ba site in the antiferromagnetic YBa2Cu3O6 at 80 K was determined. Calculation of the dipole field at the Ba site due to localized antiferromagnetically ordered 0.66 μB magnetic moments at Cu(2) sites yields 47 mT.
Hydrogen-doped Antiferromagnetic YBa2Cu3O7-δHx as Studied by Proton NMR and Cu NQR
Authors: Niki Haruo , Tomiyoshi Shoichi , Shinohara Takeshi , Omori Mamoru , Kajitani Tsuyoshi , Kyan Hiroshi , Hamagawa Takeshi , Odahara Hirotaka
Published: February 2015

of the C u(l) site have been measured on the antiferromagnetic phase of a powdered sample of hydrogen-doped tetragonal YBa2Cu3O6.1H0.14 between 5 and 300 K. The line width, Δω, of 1H NMR increases abruptly below 20 K. The enhancement of T2
-1 and that of T1
-1 of 63Cu (1) NQR occurs around 20 K and 40 K, respectively. The nuclear magnetization does not recover in a simple exponential manner below 80 K. The predominant mechanism governing T1 below 80 K was found to be the fluctuating magnetic field which originates from the staggered Cu2+ moments in either the Cu(l) oxygen-deficient layer or the Cu(2)O2 plane induced by the hole doping effect. These enhancements and the abrupt increase in Δω are attributed to this fluctuating magnetic field.