bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modern Band Theory of Disordered Alloys: Basic Concepts Including a Discussion of Momentum Densities
Authors: Bansil A. 
Published: February 2015

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
The Rotational Spectrum of 2,2-Dimethylthiirane
Authors: Hartwig H. , Dreizler H. 
Published: February 2015

Abstract
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

Abstract
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

Abstract
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.
Structure of the Molten NaCl-MgCl2
Authors: Takagi Ryuzo , Tomita Masato 
Published: February 2015

Abstract
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

Abstract
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

Abstract
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.
Notizen: Investigation of BDH Zinc for Hydrogen Isotope Analysis by Mass Spectrometry
Authors: Tanweer A. 
Published: February 2015

Abstract
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.
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
On the Reconstruction of NQR Nutation Spectra in Solids with Powder Geometry
Authors: Robert H. , Pusiol D. , Rommel E. , Kimmich R. 
Published: February 2015

Abstract
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.