bluuebunny/crossref_metadata_2025_split huggingface dataset:
Doppler Line Broadening from the Asymptotic Cauchy Distribution
Authors: Lavenda B. H. 
Published: February 2015

Abstract
The half-width of Doppler broadening is derived without assuming Maxwell's distribution for the velocities of the radiating atoms. In the absence of Doppler broadening there is only natural radiation broadening, and by thermalizing the asymptotic Cauchy distribution one obtains asymp-totic double exponential distributions for the largest (blue) and smallest (red) values of the frequency shift. These are the relevant extreme value distributions for largest and smallest values. Since the mean values are opposite and equal there is a zero shift in the line, while the standard deviation gives an expression for the half-width to within 2% of the Doppler half-width obtained from the Maxwellian when the damping coefficient is taken as the ratio of the natural radiation damping coefficient to the fine structure constant.
Deterministic Chaos in the Dynamics of a Freely Jointed Chain with Three Degrees of Freedom
Authors: Siegert Georg R. , Winkler Roland G. , Reineker Peter 
Published: February 2015

Abstract
The dynamics of a short freely jointed chain of three segments is investigated numerically. The chain consists of mass points connected by massless rigid rods, its initial and final points being fixed. Thus the chain represents a holonomically constrained system with three degrees of freedom. It is shown that the motion of the mass points can be chaotic; the occurrence of chaos depends on the initial conditions of the motion, the end-to-end distance of the chain, and the angular momentum about the axis of the stretching direction. Moreover, the chain more likely exhibits regular than chaotic behavior. The numerical results are presented in the form of Poincare surfaces of section, including the use of a slice technique, as well as in the form of power spectra.
High-Resolution Vibrational Spectra of Furazan III. The A1 Fundamentals v3 at ~ 1316 cm-1 and v4 at ~ 1036 cm-1 from Fourier-Transform Infrared Spectroscopy
Authors: Stiefvater Otto L. 
Published: February 2015

Abstract
With prior information on vibrationally excited states from DRM microwave spectroscopy, two B-type high-resolution FT-IR bands of furazan were examined to yield the band origins v0
3 = 1316.2254 cm-1 and v0
4 = 1036.1689 cm-1 with an estimated absolute uncertainty of ±0.0001 cm-1 . The rotational and distortion constants of both fundamental states were refined by the combination of rotational with rovibrational data in the least-squares fits of the bands.
NMR and Dilatometric Studies on [N(CH3 )4]3 M2X9 (M = Sb, Bi; X = Cl, Br)
Authors: Medycki W. , Jakubas R. , Piślewski N. , Lefebvre J. 
Published: February 2015

Abstract
Thermal expansion studies on [N(CH3)4]3Sb2Cl9 and [N(CH3)4]3Sb2Br9 are reported. The relaxation times 1H T1 were measured for [N(CH3)4]3 Bl2Cl9 , [N(CH3)4]3Sb2 Br9 , and [N(CH3)4]3 Bi2 Br9 in the temperature range 100-290 K. To interpret the T1 data on [N(CH3)4]3Bi2Cl9 the method of T1 calculation reported by Takeda et al. has been applied successfully. Two different, inequivalent types of [N(CH3)4]3
+ cations for all tetramethylammonium crystals are found.
Highly Resolved MR Imaging of Arbitrary Subregions in Large Objects by a Whole-Body Imager
Authors: Pfeffer Karin , Pfeffer Markus , Jung Wulf-Ingo , Lutz Otto , Schick Fritz 
Published: February 2015

Abstract
Highly resolved images of defined regions of interest within extended objects were obtaind with a 1.5 T whole-bode imager and standard hardware. The high-resolution spin echo imaging sequence avoids aliasing and allows pixel resolutions down to 39 µm which are confirmed by phantom measurements. The application of the sequence to large biological objects such as, for example, an amaryllis bulb results in images which provide much detail which could not be resolved with standard sequences.
Composite Particle Theory in Quantum Electrodynamics
Authors: Stumpf H. , Fauser B. , Pfister W. 
Published: February 2015

Abstract
Without use of pathintegral formalism a composite particle effective dynamics is developed for spinor quantum electrodynamics. By algebraic evaluation of spinor quantum electrodynamics in Coulomb gauge a corresponding functional equation is derived. The commutation rules for the transversal electromagnetic field can be deduced as a consequence of this formalism. By application of weak mapping theorems the QED functional equation can be mapped onto a functional equation for composite particles with mutual interaction and interaction with the electromagnetic field. The formalism is demonstrated for positronium states. The incorporation of renormalization into this scheme is verified.
14N Nuclear Quadrupole Coupling Constants of Acetamide and α-Fluoroacetamide
Authors: Heineking N. , Dreizler H. 
Published: February 2015

Abstract
The 14N nuclear quadrupole hyperfine structures in the rotational spectra of acetamide, CH3CONH2 , and α-fluoroacetamide, FCH2CONH2 , have been resolved. From the observed patterns, the quadrupole coupling constants have been determined with high precision. The results provide evidence of considerable derealization of the nitrogen lone electron pair. For acetamide, the full coupling tensor has been determined from a combined analysis of the ground and first excited state of the methyl group internal rotation.
The spectrum of α-fluoroacetamide-[15N] has been obtained for the first time, and a refined structure is proposed.
An Investigation of the Structure of Aqueous Electrolyte Solutions by Statistical Geometry
Authors: Kiselev M. , Poxleitner M. , Seitz-Beywl J. , Heinzinger K. 
Published: February 2015

Abstract
Statistical geometry is employed for a quantitative description of deviations from regular octahedrality of water around monovalent ions and from regular tetrahedrality of solvent water around water molecules. For these deviations a new criterion is presented by taking into account octahedral and tetrahedral spatial symmetry groups. A geometrical definition of structure making and structure breaking is proposed and illustrated on the basis of molecular dynamics simulations of 2.2 molal aqueous KCl and LiI solutions with the flexible BJH model of water.
Electron Distribution in Some Zincblende-Type Crystals
Authors: Uno Ryosei , Ozawa Haruo , Ishigaki Jun , Yukino Ken 
Published: February 2015

Abstract
The elctron density distribution in crystalline ZnSe and ZnTe has been measured by X-ray diffraction on powder samples and is compared with the results for other zincblende-type crystals. It is shown that the data for these two compounds corroborate the linear dependence on the bond charge that has been found earlier for the effective atomic charge from infrared reflection measurements, the optical dielectric constant and the ionicity estimated from pseudopotential band theory.
Charge Density Study on Bullvalene (C10H10 )
Authors: Koritsánszky T. , Buschmann J. , Luger P. 
Published: February 2015

Abstract
Low-temperature single-crystal neutron and X-ray diffraction data were collected for bullvalene (Figure 1). X -N Fourier and multipole static deformation electron density maps were calculated and compared. Atomic mean-square-displacement parameters were analysed in the framework of the rigid-body motion model and the residual amplitudes (UOBS - UTLS) were graphically interpreted. The preliminary results presented here reveal either a bias in the X-ray anisotropic displacement parameters (ADPs) due to improper modelling of the electron density or unresolved errors in the neutron data.
Electrostatic Properties of Molecules from the X-Ray Charge Density. Application to Deuterated Benzene, 1-Alanine and d,l-Histidine
Authors: Su Zhengwei , Coppens Philip 
Published: February 2015

It has been shown (Z. Su and P. Coppens, Acta Cryst. A 48, 188 (1992)) that the electrostatic potential, the electric field, and the electric field gradient (EFG) can be expressed in closed forms in terms of the positions and the charge-density parameters of individual atoms, whose aspherical density is described by a pseudoatom model (e.g., N. Hansen and P. Coppens, Acta Cryst. A 34, 909
(1978)). A F o r t r a n program Molprop91 based on this method has been written (Z. Su, State Univ. of New York at Buffalo 1991). The method has been applied to the title compounds. Low-temperature X-ray diffraction data of fully deuterated benzene (G. A. Jeffrey, J. R. Ruble, Y. Yeon, and C. Lemann, private communication, 1991), /-alanine (R. Destro, R. E. Marsh, and R. Bianchi, J. Phys. Chem. 92, 966 (1988) and d,/-histidine (N. Li, Ph.D. thesis, State University of New York at Buffalo 1989) were analyzed using the least-squares deformation density refinement program Lsmol90 (a
modified version of M o l l y ) . Molprop91 was subsequently used to calculate the electrostatic-potential maps in selected sections, and at the nuclear positions. For the latter, the EFGs were also evaluated. The electrostatic potentials were used to fit net atomic charges and estimate the molecular energies. Errors in the derived quantities are given.
Spin Transfer through Hydrogen Bonding in [CO(NH3)5(OH2)][Cr(CN)6] ?
Authors: Figgis B. N. , Kucharski E. S. , Vrtis M. 
Published: February 2015

Abstract
A polarised-neutron diffraction experiment on [Co(NH3)5(H2O)][Cr(CN)6] shows the unexpected features of spin populations on the cobalt ((0.5(2) e) and the "ammine" hydrogen (0.8(1) e in total) atoms. A local density approximation DV-Xα calculation on a unit that models the molecular geometry in the crystal returns features that are broadly in agreement with the experiment. The calculation also reproduces the major features of a charge density experiment on the complex, including the low (±1.6 e) charges on the ions, in place of the formal ±3 e.
Nonnuclear Maxima in the Charge Density
Authors: Edgecombe Kenneth E. , Smith, Jr. Vedene H. , Müller-Plathe Florian 
Published: February 2015

Abstract
Basis-set and electron-correlation effects on the appearance and disappearance of nonnuclear maxima in the electron density are examined in Li2 , Na2 , Na4 and Na5 . It is shown that nonnuclear attractors can be removed in all cases except Li2 . The appearance of a pseudoatom in a lithium molecule correlates remarkably well with the size of the region, in an atomic calculation, of V2r(r) for the valence shell of the atom. This and the fact that the pseudoatom is also present in the promolecule indicate that the pseudoatoms are remnants of, or in fact are portions of, atoms that are not perturbed enough in the molecule to remove an essentially atomic characteristic.
Electron Charge and Current Densities, the Geometrie Phase and Cellular Automata
Authors: Sukumar N. , Deb B. M. , Singh Harjinder 
Published: February 2015

Some consequences of the quantum fluid dynamics formulation are discussed for excited states of atoms and molecules and for time-dependent processes. It is shown that the conservation of electronic current density j(r) allows us to manufacture a gauge potential for each excited state of an atom, molecule or atom in a molecule. This potential gives rise to a tube of magnetic flux carried around by the many-electron system. In time-dependent situations, the evolution of the electronic density distribution can be followed with simple, site-dependent cellular automaton (CA) rules. The CA consists of a lattice of sites, each with a finite set of possible values, here representing finite localized elements of electronic charge and current density (since the charge density r

no longer suffices to fully characterize a time-dependent system, it needs to be supplemented with information about the current density j).Our numerical results are presented elsewhere and further development
is in progress.
A Comparison between Polyatecylene and Polycarbonitrile
Authors: Springborg Michael 
Published: February 2015

Abstract
Results of a theoretical, comparative study of the electronic properties of trans-polyacetylene and polycarbonitrile are reported. Polyacetylene consists of zigzag chains of CH units, whereas polycarbonitrile has every second CH unit replaced by an N atom. Ground-state properties (structure, electronic bonds and bands, densities of states, momentum distributions, and reciprocal form factors) of the periodic, infinite, isolated chains are studied by means of first-principles, density-functional calculations. It is demonstrated how the presence of the (nitrogen) heteroatoms in the backbone of polycarbonitrile leads to a partial localization of the electrons. In order to investigate charged chains, model calculations are subsequently performed. These indicate solitons but not polarons to be stable. In total, the analysis demonstrates how the combination of information that can be obtained from various experiments provides a detailed description of the compounds.
On the Inference of the One-Particle Density Matrix from Position and Momentum-Space Form Factors
Authors: Schmider Hartmut , Smith, Jr. Vedene H. , Weyrich Wolf 
Published: February 2015

Abstract
A modification of a recently developed method for the least-squares reconstruction of a one-particle reduced density matrix from experimentally accessible expectation values is applied to the test systems of atomic beryllium and neon. The improvement of the resulting matrices through inclusion of electron correlation is demonstrated. Their quality is judged by comparison of the moments of the position and momentum densities and of the spherically averaged density matrix in a suitable representation.
Nondiagonal Response of Electrons by Coherent Inelastic X-Ray Scattering
Authors: Kaprolat A. , Schülke W. 
Published: February 2015

Abstract
The experimental knowledge of the dielectric response of electrons within a solid is up to now mainly gained by inelastic scattering experiments, using a plane wave as initial state of the probe particle. These experiments allow the measurement of the dynamical structure factor, related to diagonal elements of the inverse dielectric matrix ε-1. We present a new type of scattering experiment that uses as initial state of the probe a standing wave field, thus allowing the experimental determination of non-diagonal elements of ε-1. Comparison of the experimental results with a plasmon-band model leads to direct experimental evidence for plasmon-banding in Si.
Recent Advances in Compton Scattering
Authors: Dobrzyński L. 
Published: February 2015

Abstract
A review of achievements in the field of Compton spectrometry in the years that elapsed from the last Sagamore meeting (1988) is presented. Some physical problems that have either appeared as new or became clarified are described. Special emphasis is put to the results obtained by means of magnetic Compton scattering.
Performance of the Compton Spectrometer at HARWI/HASYLAB
Authors: Schmitz J. R. , Schulte-Schrepping H. , Berthold A. , Mourikis S. , Schülke W. 
Published: February 2015

Abstract
Performance, resolution and spectral throughput both of the sagittally focusing monochromator and of the alternately installed two analysing systems, a Cauchois-type cylindrically bent crystal analyser for Compton-profile measurements, and a spherically bent crystal analyser for S(q, ω)-measurements, of the new Compton spectrometer at the HARWI (harter Röntgen Wiggler) of the DORIS storage ring are presented together with two typical applications.
The Dynamic Structure Factor of LiC6 and KC8 : Inelastic Synchrotron X-Ray Scattering Results
Authors: Berthold A. , Gabriel K.-J. , Schülke W. 
Published: February 2015

Abstract
The dynamic structure factor S(q, ω) of electrons in lithium-intercalated graphite (LiC6) and potassium-intercalated graphite (KC8) for momentum transfer q || c-axis has been measured by inelastic synchrotron X-ray scattering. The dielectric function ε(q, ω) was deduced from the data and compared with ε(q, ω) of pristine graphite.
The main feature in the different Im [ε(q, ω)]-spectra, a more or less intense peak around 14 eV, can be assigned to maxima of the symmetry-projected joint density of occupied and unoccupied electron states near the Fermi level. Knowing the position of the occupied bands by photoemission experiments, predictions about the unoccupied π and interlayer states can be made.
In the case of LiC6 , a shift and broadening of the first Im [ε(q, ω)]-peak was found, which can be explained by a decrease of the energy of the interlayer-band because of the strong hybridization of this graphite-derived band with the Li metal 2s-band.
In the case of KC8 , a weakening of the first peak of Im [ε(q, ω)] was observed, which we attribute both to a decreasing overlap of the occupied s-derived state with the empty interlayer state and to a change of symmetry of the occupied π-derived states as well as of the empty rc-derived states.
Anisotropy of the Electron Momentum Distribution in Pyrolytic Graphite Studied Using a WKa1 Spectrometer
Authors: Manninen S. , Honkimäki V. , Suortti P. 
Published: February 2015

Abstract
A new spectrometer construction based on a high-voltage W-anode x-ray tube has been used to measure the directional Compton profiles of a pyrolytic graphite crystal. Owing to the focusing geometry, the monochromatic WKα1 t beam is very well collimated, which improves the momentum resolution compared with conventional241 Am spectrometers, operated almost at the same energy. The experimental anisotropy in the basal plane and in the direction of the c-axis is found to be very close to that of a recent calculation, based on the pseudopotential local-density-functional model.
The Asymmetry of the Compton Profiles and its Dependence on the Geometrical Resolution
Authors: Anastassopoulos D. L. , Priftis G. D. 
Published: February 2015

Abstract
The asymmetry of Compton Profiles (CPs) measured with a 60-keV 241 Am source on an Al monocrystal, cut along [111], is reported for three different geometrical resolutions. It is found that the geometry of the spectrometer has a substantial effect on the asymmetry of the CP. The better the geometrical resolution the smaller the asymmetry of the CPs.
Positron Annihilation Studies of the Electronic Structure and Fermiology of High-Tc Superconductors
Authors: Smedskjaer L. C. , Bansil A. 
Published: February 2015

Abstract
We discuss the application of the positron annihilation angular correlation (ACAR) spectroscopy for investigating the electronic structure and Fermiology of high-Tc superconductors, with focus on the YBa2Cu3O7 system where most of the experimental and theoretical work has to date been concentrated. Detailed comparisons between the measured 2D-ACAR positron spectra and the corresponding band theory predictions show a remarkable agreement (for the normal state), indicat-ing that the electronic structure and Fermi surface of this material is described reasonably by the conventional picture.
High-Resolution Neutron Spectroscopy for the Investigation of Hydrogen Diffusion and Molecular Rotations in Solids
Authors: Springer T. 
Published: February 2015

Abstract
An introductory survey on applications of high-resolution neutron spectroscopy is presented, dealing with the motion of hydrogen in solids, namely concerning (i) random rotational motions or stationary tunneling states of NH+
4-ions or CH3-groups, and (ii) diffusion of hydrogen in alloys. For the rotation of hydrogenous groups in solids, at higher temperatures rotational jumps can be found, whereas quantum states are observed by μeV-spectroscopy at temperatures below 50 K. On the other hand, hydrogen diffusion does not reveal pronounced evidence of quantum effects, except for hydrogen in a metal containing impurity atoms.
Deep Inelastic Neutron Scattering Studies of Atomic Momentum Distributions in Condensed Argon and Neon
Authors: Fradkin M. A. , Zeng S.-X. , Simmons R. O. 
Published: February 2015

Abstract
Using deep inelastic neutron scattering, direct measurements have been made, i) of the dynamic structure factor of a series of condensed argon samples over the temperature range 18 to 85 K, near melting (for wave-vector transfers 12 to 26 Ä -1) and ii) of liquid neon, near 27 K (for wave-vector transfers 10.4 to 27.6 Ä -1). Neutron time-of-flight chopper spectrometers were employed. Single-particle kinetic energies, £ k , can be obtained from the analysis of the Doppler-broadened recoil spectrum of the target particles. For argon the temperature dependence of £ k can be compared to expectations from theory, from thermodynamic data, and from previous neutron scattering measurements on collective vibrational modes. For liquid neon the wave-vector-transfer dependence of J{y), the longitudinal momentum distribution function, is being analyzed for final-state effects.
Investigations of the Anisotropic Optical Reflectivity of Binary and Ternary Nb-W Oxides Possessing Block-Type Crystal Structure
Authors: Rüscher C. H. , Zimmermann M. , Götte M. 
Published: February 2015

Abstract
We have studied the anisotropic optical properties of binary NbO2.5-δ (0 < δ ≤ 0.083) and ternary Nb18-εW8+εO69 (ε = 0, 1,..., 9) compounds using the polarized regular-reflection method. We observed strong anisotropic behaviour for all reduced phases. The anisotropic effect can be related to the crystallographical structure principle and to the doping of charge carriers by the reduction of oxygen (δ) or substitution of W for Nb (ε) in the binary and ternary oxides, respectively. Our results indicate that the charge carriers are confined to the structural block units. For increasing δ and ε, metal-like properties occur (δ≥ 0.1, ε > 8) in the infinite block direction only.
Experimental Investigation of the Magnetic Fluctuations in a Toroidal Plasma
Authors: Shi-yao Zhu , Chao Zhou , Cheng Wang 
Published: February 2015

Abstract
This paper presents experimental results on the magnetic field fluctuations in the KT-5C tokamak plasma, including magnetic field fluctuation frequency spectra and the radial profile of the fluctuation amplitudes. These results show that the low frequency components are dominant for the magnetic field fluctuation signals, and that the magnetic field fluctuation levels decrease towards the edge of the plasma. A remarkable influence of the gas puffing level on the amplitude of the magnetic field fluctuations was observed.
The Repulsive Potentials in Alkali Halide Molecules
Authors: Sinistri C. , Margheritis C. 
Published: February 2015

Abstract
On the basis of literature values of various spectroscopic quantities, the "experimental" five derivatives (1st to 5th) of the repulsive functions at the equilibrium distance were evaluated for the 20 alkali halide molecules, retaining the truncated Rittner model for the attractive forces. A self-con-sistency test showed that the used experimental values are reliable.
Different analytical forms of the repulsive potential were then critically evaluated by comparison with the experimental derivatives. The repulsive functions were characterized by two, three, four or five empirical parameters. It has been shown that only functions with at least three parameters are sufficiently accurate to reproduce spectroscopic quantities such as ße and γe : the classical two parameter functions appeared too crude in this context.
Enumeration of Chemical Isomers of Polycyclic Conjugated Hydrocarbons with Different Ring Sizes
Authors: Brunvoll J. , Cyvin B. N. , Cyvin S. J. 
Published: February 2015

Abstract
Polygonal systems, corresponding to completely condensed polycyclic conjugated hydrocarbons with arbitrary ring sizes, are studied. For all the cases up to four rings inclusive, the numbers of CnHS isomers are reported, as well as for some classes of the systems with five rings. Explicit combinatorial expressions and the solutions in terms of generating functions are given in some cases. These solutions were corroborated and extended by computer programming. Chemical applications are reported with references to hydrocarbons which are known in organic chemistry.