bluuebunny/crossref_metadata_2025 huggingface dataset:
Spin -Orbit Coupling in the O-
2 Anion
Authors: Schiedt J. , Weinkauf R.
Published: February 2015

We could resolve the spin-orbit splitting of 160 ± 4 cm-1 in the 2
II ground state of O2
- anions by high resolution photodetachment photoelectron spectroscopy. The observed splitting is in good agreement with the theoretically derived value. Our directly measured electron affinity of O 2 is 450 ± 2 meV and deviates within experiment errors from previous values. kHz repetition rate was applied to avoid space charge and improve electron energy resolution in a time-of-flight electron energy analyzer.
Spark Gap Pressure and Lasing Behaviour of a non -Blumlein type Nitrogen Laser
Authors: Rodrigues Silvana Vianna , Baumann Wolfram
Published: February 2015

The effect of the nitrogen or SF6 pressure in a spark gap of a small rugged free running nitrogen laser (laser gap 2.4 mm, channel length 170 mm) is studied. No significant difference between nitrogen and SF6 as spark gap chamber gases was found. With increase of the spark gap pressure from 1 to 3.5 bar the pulse energy increases from 30 to 70 μJ, at 10 kV, or from 90 to 130 μJ, at 14 kV. The maximum of the laser efficiency is found at lower breakdown voltages with higher spark gap pressures. Pre-ionization by UV light from the spark gap can be excluded, but not that from a corona discharge over the capacitor foil below the laser channel. It is shown that further effort to increase the laser output power must start from the design of a fast spark gap, well integrated into the whole discharge circuit.
Defect Chemistry of " BaCuO2" I. Oxygen Non -Stoichiometry, Cation Molecularity and X-ray Diffraction Determinations
Authors: Spinolo G. , Anselmi-Tamburini U. , Arimondi M. , Ghigna P. , Flor G.
Published: February 2015

“BaCuO2” is the key intermediate in the synthesis of the Ba2YCu3O7−δ superconductor. Its very complex crystal structure is able to accommodate a large change in oxygen content.

Oxygen non-stoichiometry of "BaCuO2" materials with 1:1 and 88:90 (Ba :Cu) molecularity has been investigated by polythermal X-ray powder diffraction coupled with isobaric-isothermal gravimetry determinations under different temperature and oxygen partial pressure conditions [300≤ T≤ 820 °C, 1 ≥ P(O2) ≥ 3 • 10-3 atm].

The 1:1 composition does not give well reproducible results, thus suggesting its polyphasic nature, at least in part of the investigated range. The results for the 88:90 ≅ 0.98 (Ba :Cu) composi­ tion are well reproducible and show that the material is single phase. Ba0.98CuO1.98 + δ is oxygen over-stoichiometric in the whole investigated [T, P(O2)] range, with a maximum value δ∼0.21. A Rietveld X-ray profile fitting is in agreement with previous single-crystal data. The trend of δ vs. P(O2) is consistent with the presence of oxygen interstitial defects on (possibly different) crystallographic sites.
From Electric Field Dependent Particle Dynamics to Bistability in the Breakdown of the Quantum Hall Effect
Authors: Riess J.
Published: February 2015

The integer quantum Hall effect (IQHE) and its breakdown (onset of dissipation) reflect general properties of the solutions of the time-dependent Schrödinger equation, where the macroscopic elec­tric field E is properly included. In particular, the dynamics of an electron in a broadened Landau band not only depends on the disorder potential but also on the value of |E|. This leads to an I n ­ dependence of the conductivities σxx and σxy, which implies that the IQHE breaks down if |E| is sufficiently high. We show that the general form of the | El-dependence of σxx and σxy can lead to jumps in the longitudinal resistance at the breakdown of the IQHE, as observed in recent experiments.
Investigation of Front Propagation in an Electrochemical System: Experiments and Numerical Simulations
Authors: Flätgen G. , Krischer K. , Ertl G.
Published: February 2015

We examined the spatio-temporal behavior of an electrochemical system in the bistable regime, in which the system might take on either a high current density state (active) or a low current density state (passive) at one value of the externally applied voltage. The transition from the passive to the active state is accompanied by accelerating fronts with sharp interfaces, whereas the reverse transition from the active to the passive state exhibits much smoother spatial variations. Also the evolution of the total current density displays qualitative differences in the two cases. Both, the differences of the spatial patterns as well as those of the total current densities are reproduced with a mathemati­cal model, which also reveals the origin of the asymmetry of the transitions: a global coupling, intrinsic in all electrochemical systems, in combination with the specific dependence of the reaction current on the electrode potential.
Attractor Merging Crisis in the Double-Scroll Oscillator
Authors: Reisner B. , Kittel A. , Lück S. , Peinke J. , Parisi J.
Published: February 2015

We investigate the transition from a mono-scroll to a double-scroll attractor observed in the chaotic dynamics of an electronic oscillator. The description in terms of an attractor merging crisis turns out to be successful. The finding is supported by the topological structure of the attractor and the scaling behavior of the mean residence time.
Dweiltime Analysis of Symmetry-Breaking Dynamical Systems
Authors: Vollmer J. , Peinke J. , Okniński A.
Published: February 2015

Dweiltime analysis is known to characterize saddles giving rise to chaotic scattering. In the present paper it is used to characterize the dependence on initial conditions of the attractor approached by a trajectory in dissipative systems described by one-dimensional, noninvertible mappings which show symmetry breaking. There may be symmetry-related attractors in these systems, and which attractor is approached may depend sensitively on the initial conditions. Dwell-time analysis is useful in this context because it allows to visualize in another way the repellers on the basin boundary which cause this sensitive dependence.
Reversible Control of Chemical Reaction Systems
Authors: Hoff Axel A. , Diebner Hans H. , Baierc Gerold
Published: February 2015

Starting from an algorithm for continuous chaos control, a reversible control method based on mutual diffusive coupling of chemical reactors is developed. With sufficient coupling strength, the proposed mutual coupling leads to control even if both reactors are of similar size. The controlling and controlled reactor exchange their roles at a certain size ratio. Insufficient coupling can lead to a more complex dynamics than that of the uncoupled reactors. This method for control via reversible coupling of chemical reactors should be implementable on a purely microscopic level.
Instabilities in a Simple Enzyme Reaction Caused by pH-Dependence
Authors: Baier Gerold , Strasser Peter , Kummer Ursula
Published: February 2015

We investigate the model of an enzymatic reaction with Michaelis-Menten kinetics and bell-shaped pH-dependence of the reaction rate. In the case of proton consumption the reaction can generate oscillations in a homogeneous reactor and turbulent spatio-temporal patterns in a reaction-diffusion environment. I n s t a b il it i e s in a S im p le E n z y m e R e a c tio n C a u s e d b y p H -D e p e n d e n c e *
EPRInvestigation of Synthetic, Doped FeS2 and RuS2 Single Crystals
Authors: Schüler M. , Dahlem J. , Siebert D.
Published: February 2015

Synthetic FeS2 and RuS2 single crystals were prepared by the flux method using PbCl2, bismut, and tellurium as different solvents. FeS2 and some RuS2 samples were doped with elementary vanadium, other RuS2 crystals with manganese and nickel. The EPR spectra revealed Mn2+ in the low-spin state and Ni2+. The lineshape of the Mn sextet turned out to be asymmetrical. In some RuS2 samples we detected an isotropic structureless rather narrow signal with a linewidth down to 0.05 mT and attributed it to the conductivity. Its lineshape becomes symmetrical and Lorentzian by grinding the samples to a polycrystalline powder. The EPR parameters of appropriate spin-Hamiltonians were determined. The intensities of the allowed and forbidden lines depended very differently on the microwave power due to different degrees of saturation.
Absorption Spectra of Co(II)Ions Doped in Magnesium Thallium Sulphate Hexahydrate
Authors: Subbaiah A. Venkata , Rao J. Lakshmana , Naidu Y. Nagaraja
Published: February 2015

The optical obsorption spectrum of Co(II) ions doped in magnesium thallium sulphate hexahy­ drate is studied at room and liquid nitrogen temperatures. The crystal exhibits characteristic absorption of the Co(II) ion in the visible and near infrared. The observed bands are assigned to transitions from the ground state 4T1g (F) to various excited quartet and doublet levels of the Co(II) ion in octahedral symmetry. The splitting of one of the bands at liquid nitrogen temperature is explained to be due to spin-orbit splitting. All band positions have been fitted by the parameters B, C, Dq and ξ.
Absorption and Fluorescence Properties of p-Substituted Stilbenes in Poly (vinyl chloride) Film
Authors: Kawski A. , Kukliński B. , Nowosielski T.
Published: February 2015

Experimental studies have demonstrated that the absorption and fluorescence spectra of linear molecules with one double bond, i.e. 4-amino-4'-nitrostilbene (ANS), 4-dimethylamino-4'-nitro-stilbene (DNS) and 4,4'-diphenylstilbene (DPS), contained in preheated to 393 K or nonheated polyvinyl chloride) (PVC) films are identical in shape and position, unlike those observed for ANS, DNS and DPS in polyvinyl alcohol) (PVA) films. For polar ANS and DNS molecules in PVC film a decrease in the emission anisotropy with growing wavelength of the fluorescence band was observed. This unusual behaviour of the emission anisotropy is accounted for by the overlap of two close emission bands from different luminescent centres, resulting from different microenvironments of the ANS and DNS molecules in PVC film. The emission anisotropy of nonpolar DPS molecule in PVC does not change within the fluorescence spectrum.
Sub-millimeter Wave Spectra of Cyanoacetylene and Revised Ground State Constants
Authors: Yamada K. M. T. , Moravec A. , Winnewisser G.
Published: February 2015

Sixteen new rotational transitions of cyanoacetylene in the ground vibrational state have been measured in the frequency region from 570 GHz to 710 GHz by the Cologne sub-millimeter wave spectrometer. The observed transition frequencies were analyzed together with unpublished millimeter wave data of our group and with the data available in the literature. Precise rota­ tional constant and the quartic and sextic centrifugal distortion constants have been determined; B = 4549.058224(37) MHz, D = 0.544110(19) kHz, and H = 0.0345(21) mHz.
A Quasi-Optical Multiplier for Terahertz Spectroscopy
Authors: Lewen F. , Belov S. P. , Maiwald F. , Klaus Th. , Winnewisser G.
Published: February 2015

The rotational K-structure (K = 0, ... 6) of the a-type transition (J = 65 - 64) of the symmetric top molecule methylcyanide, CH3CN, has been recorded at 1.2 THz employing a newly designed quasi-optical frequency multiplier. A planar Schottky diode is used as non-linear element for producing the harmonic power and is mounted in the focus of an off-axis antenna across a short single ridged waveguide. The 2nd harmonic of the fundamental frequency is filtered with adichroic plate and is focused onto the InSb bolometer after passing an absorption cell. The multiplier is driven by a high power backward wave oscillator with a fundamental frequency near 600 GHz.
Cation Distribution of ZnFe2O4 and CoFe2O4 Spinels From Anomalous X-Ray Scattering
Authors: Waseda Y. , Shinoda K. , Sugiyama K.
Published: February 2015

The distribution of Zn2+ and Co2+ cations in ferrite spinels has been determined by applying anomalous X-ray scattering (AXS) near the K absorption edges of Fe, Co and Zn. The energy dependence of the reflection intensities of ZnFe2O4, detected at the Fe K and Zn K absorption edges, can only be explained when all Zn2+ being allocated to the tetrahedral site formed by oxygens. On the other hand, the results for CoFe2O4 suggest that 78% of Co2+ occupy the octahedral site, and that the present CoFe2O4 sample is classified as inverse spinel, although a partial disorder is included. The usefulness of this AXS method coupled with the common Rietveld analysis was well-recognized by determining the cation distribution even in a system with next neighboring elements of the periodic table.
Semi-Empirical Fitting of Partial Pair Correlation Functions of Amorphous Alloys
Authors: Sváb E. , Hajdu F. , Mészáros Gy.
Published: February 2015

A semi-empirical fitting procedure has been developed and used in analysing the characteristic features of the partial structure factors of binary amorphous alloys. An analytical formula is given to fit the experimental atomic pair correlation function as a sum of Gaussians. The inverse Fourier transform of the fitted terms reproduces all features of the experimental structure function. In addition to the structural parameters, the modelling gives a quantitative explanation for the complex origin of characteristic features in the diffraction pattern such as pre-peak, pre-minimum, and split peaks in the partial structure factor.
Tunable Real Space Transfer Oscillator by Delayed Feedback Control of Chaos
Authors: Cooper D. P. , Schöll E.
Published: February 2015

It is demonstrated numerically that by using Pyragas' method of chaos self-control a stable semiconductor oscillator can be designed based on driven real-space transfer oscillations in a modulation-doped heterostructure. By application of a small time-continuous delayed feedback voltage control signal, different unstable periodic orbits embedded in the chaotic attractor can be stabilized. Thus different modes of self-generated periodic voltage oscillations can be selected by choosing an appropriate delay time. This provides tunability to different discrete frequencies.
Explosive Instability in Superposed Fluids in Hydromagnetics
Authors: Gill Gurpreet K. , Trehan S. K.
Published: February 2015

We study the resonance interaction between two marginally unstable modes of small but finite amplitude waves in the Kelvin-Helmholtz flow model using the method of multiple scales. We find that, as magnetic field increases, the amplitudes of the disturbance diverge at a very high rate while for a fluid of higher density ratio e, the amplitudes diverge very slowly.
The 33S Nuclear Quadrupole Hyperfine Structure in the Rotational Spectrum of 32S, 33S Dimethyl Disulfide
Authors: Hartwig H. , Kretschmer U. , Dreizler H.
Published: February 2015

We investigated the rotational spectrum of 32S, 33S dimethyl disulfide in natural abundance by molecular beam Fourier transform microwave spectroscopy. We were able to determine the com­plete 33S quadrupole coupling tensor, the rotational and centrifugal distortion constants and the internal rotation parameters of the two methyl tops. The rotational constants were found to be A = 8113.8847(23) MHz, B = 2800.6203(30) MHz and C = 2557.2245 (32) MHz. The results are compared with former publications.
p, T-Dependence of Self Diffusion in Mixtures of Hexane/Ethanol and Hexane/Dimethylether
Authors: Heinrich-Schramm A. , Price W. E. , Lüdemann H.-D.
Published: February 2015

Self-diffusion in ethanol/hexane and dimethylether/hexane mixtures of various compositions has been measured at 215-350 K and up to 200 MPa. Qualitative analysis of the results indicates that, as expected, hydrogen bonding retards the self-diffusion of ethanol in the mixture, especially at the low temperatures. Dimethylether shows a slight effect of dipole-dipole interactions on the self-diffu­sion, as seen by a higher ΔE* value than for the alkane. However there is no significant difference in the pressure dependence for both mixtures. This is shown by considering the ratio of the two diffusion coefficients, which suggests that, contrary to what is observed for pure alcohols, pressure has little effect upon the hydrogen bonding of ethanol in the mixture. In additon, there is surprisingly little concentration dependence on the ratios for either mixture.
Stability of (Ni1_xLix)(Li1–yNiy)02Ordered Solid Solution
Authors: Massarotti V. , Capsoni D. , Bini M.
Published: February 2015

The stability of ordered solid solutions (OSS) with LiNiO2 structure has been studied in a wide range of the lithium cationic fraction (0.22< xt < 0.42). The OSS is obtained from the reactive system Ni0/Li2CO3 at 800 °C starting with high nominal lithium content (xt = 0.5). By analysis of the decrease of x, observed after annealing, during which evaporation and a contact reaction occurs, structure-composition relationships can be obtained.

The transformation of the ordered phase, due to a cation exchange process, is observed for xt < 0.31 by accurate X-Ray powder pattern analysis (Rietveld method). By increasing the annealing time (decreasing lithium content), the data can be explained on the basis of progressive formation of the simple solid solution (SSS) with only one cation site and halved c axis value. The variations of structural parameters during the transformation are compared with those reported in the literature. The coherence domains of the OSS become smaller and the phase percentage decreases, while the SSS percentage increases. The rate of such a process can be well described on the basis of a two dimensional diffusion mechanism.
2 D 31P Exchange NMR: A new Approach for a Direct Probing of the Connectivities of Qn Units in Glasses
Authors: Born R. , Feike M. , Jäger C. , Spiess H. W.
Published: February 2015

Recently, 31P two-dimensional (2D) NMR has been proposed as a powerful tool for direct investigations of the connectivities between the Qn units in glasses, i.e. the medium-range order. In this paper, the principles of these experiments and applications to both polycrystalline Mg2P2O7 and a Na2O-P205 glass are demonstrated, including a theoretical description and modelling of the polarization transfer between the two inequivalent phosphorus sites in the magnesium pyrophosphate.
A New Weak Field Double Resonance NMR Spectrometer
Authors: Akay Cengiz , Yalçiner Aytaç
Published: February 2015

Weak field NMR and double resonance spectrometers are mostly homemade. In this work, some electronic units of such a spectrometer operating at 1.437 mT were designed and realized by includ­ing new integrated circuits: an audio generator, digital sweep generator, digital additional field and delay unit, Quartz generator, NMR detector(Q-meter), AF-narrowband amplifier, phase shifter and phase sensitive detector.
On the Use of Pulsed Field Gradients in a High-Field NMR Spectrometer to Study Restricted Diffusion in Zeolites
Authors: Kärger J. , Bär N.-K. , Heink W. , Pfeifer H. , Seiffert G.
Published: February 2015

A probe system is described which allows the application of magnetic field gradient pulses with amplitudes up to 24 T/m for self-diffusion measurements by means of a PFG NMR spectrometer operating at a proton resonance frequency of 400 MHz. It is demonstrated that PFG NMR measurements in the high field of a superconducting magnet necessitate precautions which are of minor relevance for measurements with iron magnets. Taking advantage of the large gradient intensity and the high sensitivity in signal detection of the described system, attenuation patterns of the NMR spin echo are observed for the first time that represent the PFG NMR analogue of the diffraction pattern of a sphere.
Oxidation of Fe-Cr-Al and Fe-Cr-Al-Y Single Crystals
Authors: Grabke H. J. , Siegers M. , Tolpygo V. K.
Published: February 2015

Single crystal samples of the alloy Fe-20%Cr-5%Al with and without Y-doping were used to study the "reactive element" (RE) effect, which causes improved oxidation behaviour and formation of a protective Al2O3 layer on this alloy. The oxidation was followed by AES at 10-7 mbar O2 up to about 1000 °C. Most observations were peculiar for this low pO2 environment, but yttrium clearly favors the formation of Al-oxide and stabilizes it also under these conditions, probably by favoring its nucleation. The oxides formed are surface compounds of about monolayer thickness, not clearly related to bulk oxides.

Furthermore, the morphologies of oxide scales were investigated by SEM, after oxidation at 1000°C for 100 h at 133 mbar O2. On Fe-Cr-Al the scale is strongly convoluted and tends to spalling, whereas the presence of Y leads to flat scales which are well adherent. This difference is explained by a change in growth mechanism. The tendency for separation of oxide and metal was highest for the samples with low energy metal surface, i.e. (100) and (110), the scale was better adherent on the (111) oriented surface and on the polycrystalline specimen, since in the latter cases the overall energy for scale/metal separation is higher.

All observations, from the low and from the high pO2 experiments, are discussed in relation to the approximately ten mechanisms proposed in the literature for explanation of the RE effects.
The Structural and Dynamic Properties of some Transition Metal Aqua Cations: Results from Neutron Scattering
Authors: Neilson G. W. , Ansell S. , Wilson J.
Published: February 2015

The following paper comprises a survey of the role neutron scattering methods have played to help understand the origins of the diverse properties of electrolyte solutions which contain transition metal cations. It is seen how neutron diffraction and isotopic substitution is able to resolve the local structure around contrasting ions, such as Cr3+ , Ni2+, Fe3+ , Fe2+, Cu2+, without recourse to sophisticated modelling procedures. Quasielastic neutron scattering (QNS) provides insight into the dynamics of the protons in solution. The results enable one to distinguish between cations whose water molecules are coordinated on time scales larger than 5 x 10-9 s, shorter than 10-10s, or intermediate between those two limits. QNS also provides information on the existence of a second relatively short-lived hydration shell distinct from the bulk water.
A Raman Study of Alcoholic Lithium Perchlorate Solutions in the Glassy State
Authors: Kanno H. , Honshoh M. , Yamauchi S.
Published: February 2015

Raman spectra of alcoholic lithium Perchlorate solutions (alcohol = methanol and ethanol) were measured as a function of LiClO4 concentration. The Raman band due to nearly free hydrogen bonds shows peculiar concentration dependences: (1) its frequency shifts with LiClO4 concentration in contrast to alcoholic LiX solutions (X = CI and Br), in which the Raman band due to solvated halide ions shows little frequency change with LiX concentration, and (2) the half band width shows anomalous changes with LiX concentration.

Non-ionized LiClO4 species in alcohol coupled with the changes of solution structure are the major cause for this peculiar behavior.
The Structure of Hydroxylamine – Water Mixtures
Authors: Vizoso Sergi , Rode Bernd M.
Published: February 2015

Monte Carlo simulations have been carried our for 5, 25, 50, and 75 weight% aqueous solutions of hydroxylamine. Changes in the microstructure of the solutions have been evaluated by means of radial and angular distribution functions, coordination number distributions and pair energy anal­ysis. The structure of liquid hydroxylamine is strongly altered by even small amounts of water, whereas water clusters similar to the pure water are maintained up to higher NH2OH concentra­tions. The structural entities in the mixtures are determined by hydrogen bonding and electrostatic arrangement of ligands.
Raman Spectral Studies of Aqueous Acidic Pyrazine Solutions
Authors: Brolo Alexandre G. , Irish Donald E.
Published: February 2015

Raman spectra of aqueous pyrazine have been investigated in acidic media: HCl from pH = 4 up to 11 M; HCLO4 from 0.1 M to 12 M; H2SO4 form 0.1 M to 18 M. From observation of the shifts of the bands from neutral solutions, it has been possible to identify bands uniquely characteristic of unprotonated pyrazine and its two protonated forms. The diprotonated form was only observed for high concentrations of HCLO4 and H2SO4. From bandfitting of the spectral contours it has been possible to construct the species distribution diagram and estimate the pK values. Raman bands of the three species have been identified and assigned. The results are used to explain an unassigned band at 1235 cm-1, reported by several authors, in SERS from pyrazine on silver and gold electrodes.
Raman Spectroscopic Study of the Ion Association of Lithium Sulfate Aqueous Solutions
Authors: Rull Fernando
Published: February 2015

A Raman spectroscopic study of Li2SO4 aqueous solutions as function of concentration and temperature was performed. The dynamic properties of the sulfate ions were studied by a band profile analysis of their internal modes using Fourier transform methods. This analysis reveals the perturbation of the SO4
-2 vibrations due to ionic interactions. From the v1 (SO4
-2) band profile the spectroscopic ionic association constant was calculated in the range from 5 to 80 °C. The large difference found between the values thus obtained for the association constant and the values obtained from macroscopic measurements is interpreted, assuming that Raman spectra reflect only the short-range forces acting on the ions. Using the Bjerrum equation to calculate the contribution for the long-range forces, good agreement is found between the spectroscopic and macroscopic results.
Effects of Pressure, Temperature, and Concentration on the Viscosity of Aqueous Ammonium Bromide Solution
Authors: Yoshimura Yukihiro , Sawamura Seiji , Taniguchi Yoshihiro
Published: February 2015

The viscosity of aqueous ammonium bromide solutions is measured at 0.1-1.0 mol kg-1, 278.2-323.2 K, and 0.1-375 MPa, using a high-pressure rolling-ball viscometer. The activation energy (Ev) for viscous flow and Jones-Dole's B coefficient are estimated. Ev against pressure yields a concave curve with a minimum and B yields a convex one with a maximum. These phenomena are attributed to pressure, temperature, and concentration effects on the water-structure.
Bose -Einstein Condensation and Condensate Tunneling
Authors: Grossmann Siegfried , Holthaus Martin
Published: February 2015

We consider Bose-Einstein condensation in a small cube and describe effects induced by the con­ finement. We also sketch an analogue of the Josephson effect for neutral particles, which can be realized when two almost degenerate states in a double well potential are occupied by a macroscopic number of Bosons. PACS number: 05.30.Jp
Computer Simulation of a Simple Model for Rotational Moment Fluctuations in an Associating Liquid
Authors: Köhne H.-G. , Stockhausen M.
Published: February 2015

With regard to the interpretation of dielectric relaxation spectra of associating liquids such as alcohols, a two state model for the rotational tumbling motion of a dipole is considered: The moment (of constant magnitude) is assumed to undergo stochastic tumbling during a "free" state, alternating with an "associated" state where for a certain residence time the rotational motion can be neglected. One particle autocorrelation functions according to that model are calculated numerically. In any case, they can well be described as sum of (at most) two exponentials. The corresponding parameters are given as function of "association" probability and residence time
Thermodynamic Excess Functions for Quasiternary Solid Solutions of Type M(X,Y,Z) I. The System Pb (S,Te,Se)
Authors: Leute Volkmar
Published: February 2015

Abstract The excess free enthalpy of quasiternary systems of type M (X, Y, Z) with two sublattices, a mixed one (X, Y,Z) and a pure one (M), will be described in two ways: (1) by the interaction parameters of the three subregularly treated quasibinary subsystems and by one ternary parameter, and (2) by the cluster energies of 10 pyramidal clusters.

It is shown that, for the spinodal miscibility gap in the special system Pb (S, Te, Se), both versions yield satisfying accordance of experiments and calculated results
2H and 14N NMR Studies of the Dynamics in the Incommensurate Phases of Betaine Calciumchloride Dihydrate
Authors: Häcker U. , Michel D. , Hölzer K.-P. , Petersson J.
Published: February 2015

2H and 14N NMR spin-lattice relaxation rates were measured in the structurally incommensurately (IC) modulated phases of deuterated and undeuterated betaine calciumchloride dihydrate, respectively. The results are related to the elementary excitations of these phases. The presence of low-frequency phase fluctuations of the modulation wave leads to higher spin-lattice relaxation rates compared with the high-temperature normal phase and the commensurate (C) phases. The corresponding "phason" contributions are found to be nearly constant in the whole IC phases. In the IC phases near the transitions to the C phases the relaxation rates decrease due to the formation of the soliton lattice. This interpretation is in agreement with the results of previous dielectric measurements
Deuteron NMR Spectra of ND4 Tunneling at Low Frequenciesin (ND4)2SnBr6
Authors: Lalowicz Z.T. , Serafin R. , Punkkinen M. , Vuorimäki A. H. , Ylinen E. E.
Published: February 2015

Deuteron NMR spectra of slowly tunneling ND4
+ ions are analysed. Spectra are calculated as functions of the tunneling parameters which are the tunneling frequencies about the symmetry axes C2 and C3 of the tetrahedral ion. The structure and splittings within the ground torsional level (GTL) are obtained by fitting the spectra of (ND4)2SnBr6. Comparison with the GTL structure obtained before for NH4
+ in the same compound gives the isotope reduction factor of the tunneling frequency about 200.
XPS Investigations on Solid and Vacuum Deposited, Oxidized and Non-oxidized Palladium
Authors: Kintrup Jürgen , Züchner Harald
Published: February 2015

X-ray photoelectron spectroscopy (XPS) has been carried out to study the reaction of differently prepared palladium samples (solid and film Pd) with atmospheric oxygen. A careful curve fitting of the measured Pd-3d5/2 peak allows to separate the Pd-3d5/2 peak for Pd in surface PdO from the dominant Pd-3d5/2 peak of the non-oxidized bulk palladium and to determine the chemical shift of the "oxidized" Pa line with high accuracy. Differences in the chemical shifts for the surface PdO on solid and film palladium are explained by a different charging caused by the photoelectric effect in XPS measurements. The smaller charging effect observed for film palladium as compared to solid palladium indicates a stronger oxygen bonding to the (rougher) film palladium. The strong Pd-O bonding seems to be an essential reason for the reduced hydrogen-permeability of film palladium compared to solid palladium
Enhanced Sensitivity of Zero -Field NMR Spectroscopy at High Magnetic Fields
Authors: Ernst H. , Fechtelkor M. , Fenzke D. , Freude D. , Knorr B. , Kolley H. , Pfeifer H.
Published: February 2015

After reviewing the basic principles of zero-field NMR spectroscopy at high magnetic fields (ZFHF NMR) as introduced by Robert Tycko, a 2-dimensional extension of this method is described which enhances its sensitivity by at least one order of magnitude. The essential point is a combination of the original pulse program including sample rotation with a Carr-Purcell pulse sequence during the acquisition time. Experimental results are given for the proton resonance of meta-C6H2D4 dissolved in C6D6 at 245 K
Depolymerization Kinetics of Glass-Forming Chalcogenide Melts. Coherence TYansfer NMR Studies of Phosphorus Selenide
Authors: Maxwell Robert , Erickson Hans , Eckert Hellmut
Published: February 2015

The kinetics of the depolymerization of a glass-forming phosphorus selenide melt containing 48 at.% phosphorus have been studied using one- and two-dimensional coherence transfer spectroscopic methods. The depolymerization leads to the creation of molecular P4Se3. Two-dimensional spectroscopy indicates that these units are in slow exchange with the residual polymeric matrix, and corresponding rate constants are extracted from temperature dependent one-dimensional coherence transfer experiments. The results are quantitatively consistent with previous temperature-dependent NMR lineshape studies, yielding an activation energy of 109 kJ/mol
Progress in Structural Elucidation of Glasses by and 1B Satellite Transition NMR Spectroscopy
Authors: Kunath-Fandrei G. , Ehrt D. , Jäger C.
Published: February 2015

The structure of Na2O-Al2O3-B2O3 and Na2O-Al2O3-P2O5 glasses with 70 mole% B2O3 or P2O5 and varied Na/Al ratio is investigated using standard 31P MAS NMR and 27Al and UB Satellite Transition NMR spectroscopy. The role of the two network formers on the glass structure is discussed. For the AlOx units and BO3 and BO4 groups both chemical shifts and quadrupole interaction parameters including their distribution widths are reported. Besides this, the advantages of Satellite Transition spectroscopy are demonstrated both for 27A1 and 11B NMR
CP/MAS NMR of Heavy Spin-1/2 Nuclei at B0 = 2.35T
Authors: Ambrosius Frank , Klaus Elke , Schaller Torsten , Sebald Angelika
Published: February 2015

Perspectives of CP/MAS NMR at low external magnetic field (B0=2.35T) are discussed. Applications are illustrated for the case of heavy spin-1/2 nuclei such as 195Pt and 199Hg: 195Pt and 199Hg CP/MAS spectra of a variety of organometallic compounds are reported. Aspects of shielding anisotropics, of 195Pt-35/37Cl interactions and of 31P-M (M=Cd, Hg, Pt) coupling in transition metal phosphine complexes will be briefly addressed
Dynamic Behaviour of Tetramethylethylene Diamine (TMEDA) Ligands in Solid Organolithium Compounds: A Variable Temperature 13C and I5N CP/MAS NMR Study
Authors: Baumann Wolfgang , Oprunenko Yuri , Günther Harald
Published: February 2015

The dynamic behaviour of tetramethylethylene diamine (TMEDA) ligands in three organometallic complexes, dimeric phenyllithium, [Li(tmeda)μ-Ph]2 (1), lithium cyclopentadienide, [Li(tmeda)]C5H5 (2), and dilithium naphthalendiide, trans-[Li(tmeda)]2C10H8 (3), has been studied by CP/MAS 13C and 15N as well as 7Li MAS NMR spectroscopy of powdered samples. Two dynamic processes with free activation enthalpies of 40 and 68 kJ mol-1, respectively, were detected for 1. The first one can be assigned to ring inversion of the five-membered Li-TMEDA rings, while the second is caused by a complete rotation of the TMEDA ligands or a ring inversion of the central four-membered C-Li-C-Li metallacycle. Fast rotation of the ligands on the NMR time scale was found for 2, while 3 shows 180° ring flips of the Li-TMEDA groups, which are characterized by an energy barrier ΔG" (317) of 64 kJ mol-1
Polarizabilities of Isolated Silicon Clusters
Authors: Schäfer R. , Woenckhaus J. , Becker J. A. , Hensel F.
Published: February 2015

The static electric polarizabilities a of silicon clusters with up to 60 atoms have been measured employing a mass selective molecular beam deflection method. The polarizability per atom αN = α/N of the SiN-clusters has been investigated for Si11 and the size ranges N = 14-28, 22-34, 28-44, 34-50, 41 -58, and 42-68. The results show that the polarizability per atom decreases from N = 11 until a minimum at N≥28 is reached. The polarizability per atom increases for N > 28, passes through a maximum at N≈36 and finally converges between N≈50-70 against the value αN =1.9Å3. If the model of a homogeneous dielectric sphere is applied to the larger clusters one calculates that the value αN =1.9Å3 corresponds to a dielectric constant of ε = 3.2. This value is significantly smaller than the dielectric constant of bulk silicon εb = 11.8.

The present paper focuses on the maximum in the polarizability at N≈36. This effect is discussed with special emphasis to recent Car-Parinello calculations which have predicted cage-like silicon structures that enclose a core of several highly coordinated atoms. This structure suggests an improved dielectric sphere model where the core is represented by a smaller sphere with its own dielectric constant εc. It is shown within this model that the observed maximum in polarizability is due to a significant enhancement of the core dielectric constant to a value of εc ≈50. This enhancement is related by means of a simple model to the effect that silicon becomes metallic under high pressure
The Phase Diagram of the Quasiternary System (Sn, Pb) (S,Te)
Authors: Leute Volkmar , Brinkmann S. , Linnenbrink J. , Schmidtke H. M.
Published: February 2015

The phase diagram of the quasiternary system (Snt Pb1-k)(S,Te1-l) for 900 K is determined by X-ray diffraction and by electron microprobe analysis. Moreover, the free enthalpy faces g(k, I) for the phases with cubic rocksalt structure (cub) or with the orthorhombic SnS structure (orh) are calculated from the interaction parameters and from the orh → cub transition data of the 4 quasibinary subsystems.

The interaction parameters are also used to calculate the termodynamic factor for interdiffusion along quasibinary sections through the phase square and to calculate the energies of four-particle clusters. By application of the cluster model one obtains information on the local environment of the mixing particles and on the cluster processes that have effect upon interdiffusion
Helium Atom Scattering from CF4, CF3Cl, CF2Cl2 and CFCl3 in Crossed Molecular Bejams
Authors: Gebauer Christian , Klein Olaf , Schmidt Ralf , Seidel Wolfhart
Published: February 2015

Differential cross sections have been measured by scattering He atoms from CFnCl4-n (1≤n≤4) in crossed molecular beams. The damping of the diffraction oscillations was used to extract interaction potentials for these molecules which range from nearly isotropic to rather anisotropic. Macroscopic binary parameters, as second virial coefficients, diffusion coefficients and viscosities were calculated from these potentials
Differential Thermal Analysis and Dielectric Studies on 2-Methyl-2-Nitro-Propane under High Pressure
Authors: Büsing D. , Jenau M. , Reuter J. , Würflinger A. , Tamarit J. Li.
Published: February 2015

Differential thermal analysis and dielectric studies under pressures up to 300 MPa and temperatures of about 200 to 350 K have been performed on 2-methyl-2-nitro-propane (TBN). TBN displays an orientationally disordered phase (ODIC), solid I, and two non-plastic phases, solids II and III. The coexistence region of the plastic phase I increases with increasing pressure, whereas the low-temperature phase II apparently vanishes at a triple point I, II, III, above 300 MPa. The static permittivity increases on freezing, characterizing the solid I as an ODIC phase. In the frame of the Kirkwood-Onsager-Fröhlich theory the g-factor is about unity, discounting specific dielectric correlations. The dielectric behaviour of TBN is similar to previously studied related compounds, such as 2-chloro-2-methyl-propane or 2-brome- 2-methyl-propane
Truncated Painlevé Expansion with Symbolic Computation for a General Kadomtsev-Petviashvili Equation with Variable Coefficients
Authors: Tian Bo , Gao Yi-Tian
Published: February 2015

Able to realistically model various physical situations, the variable-coefficient generalizations of the celebrated Kadmotsev-Petviashvili equation are of current interest in physical and mathematical sciences. In this paper, we make use of both the truncated Painleve expansion and symbolic computation to obtain an auto-Bäcklund transformation and certain soliton-typed explicit solutions for a general Kadomtsev-Petviashvili equation with variable coefficients.
p, T Dependence of the Self Diffusion Coefficients and Densities in Liquid Silicone Oils
Authors: Thern A. , Lüdemann H.-D.
Published: February 2015

Self diffusion coefficients and densities from a series of commercial silicones have been studied in the temperature range between 290 and 410 K at pressures up to 200 MPa. The densities are fitted to a modified Tait equation. The self diffusion coefficients are discussed in terms of the rough hard sphere model and tested against the Rouse-model.
Ro-inversional Spectrum of Ammonia
Authors: Winnewisser G. , Belov S. P. , Klaus Th. , Urban S.
Published: February 2015

The ground state J = 2 ←1 , K = 0 and K = 1 ro-inversional spectrum of 14NH3 and 15NH3 at 1.2 THz has been measured with an accuracy of 20 kHz using the Cologne terahertz spectrometer. The measured frequencies for the K = 0 components are:

14NH3 (J, K) = a(2, 0) - s( 1,0): 1 214 852.942(20) MHz,

15NH3 (J, K) = a(2, 0 ) - s( 1,0) : 1 210 889.556(20) MHz.

In addition we have determined from saturation dip measurements of the J = 1 - 0 transition the spin-rotation constant CN = 6.7(3) kHz and the unsplit line center frequency:

14NH3 (J, K) = s( 1, 0) - a(0, 0): 572 498.163( 10) MHz.

The new results are in excellent agreement with existing high resolution Fourier transform data. The terahertz line frequencies are of considerably higher accuracy than the FT-data. by about two orders of magnitude. They will serve as future calibration lines. The ro-inversional transitions are of astrophysical interest
Nuclear Quadrupole Hyperfine Structure of the Direct /-Type Transitions of the Fulminic Acid Isotopomers H12C14N16O and H13C14N16O
Authors: Preusser Jürgen , Winnewisser Manfred
Published: February 2015

The direct I- type transitions of H133C14N16O in the vibrational states (υ4,υ5) = (01) and (03) were measured in the frequency range from 18 to 40 GHz. These transitions show a nuclear quadrupole hyperfine structure caused by the 14N nucleus, which could partially be resolved at Doppler-limited resolution. The analogous transitions of the parent species. H12C14N16O, were remeasured. They displayed a very similar hyperfine structure, also partially resolved. The hyperfine patterns of both H12C14N16O and H13C14N16O were analysed by means of contour fitting s to the absorption profiles. The parameter ηseQq, which is responsible for the splittings, is determined to be 645(20) kHz for the vibrational state (01) and 890(44) kHz for the vibrational state (03) for H12C14N16O and 642(32) kHz for (01) and 898(22) kHz for (03) for H13C14N16O. This unexpectedly large splitting parameter for states involving the large amplitude motion υ5 (HCN bending) is discussed as another consequence of the quasilinearity of fulminic acid, in view of the fact that the analogous transitions for the vibrational state (10) (NCO bending) do not split or even show a significant line broadening at the resolution used for the present measurements
Dielectric Properties of Solutions of a Binary Mixture Resorcinol/n-Dodecanol in Heptane
Authors: Ghoneim A. , Turky G. , Hanna F. F. , Stockhausen M.
Published: February 2015

The static and broadband dynamic dielectric properties of the title mixtures, which contain the diol to an only minor fraction, are reported for the whole concentration range (al-cohol mole fraction 0.1 to 1). As with similar systems, the diol leads to increased association effects.
Energy Surfaces of Ellipsoidal Billiards
Authors: Wiersig Jan , Richter Peter H.
Published: February 2015

Energy surfaces in the space of action variables are calculated and graphically presented for general triaxial ellipsoidal billiards. As was demonstrated by Jacobi in 1838, the system may be integrated in terms of hyperelliptic functions. The actual computation, however, has never been done. It is found that generic energy surfaces consist of seven pieces, representing topologically different types of invariant tori. The character of the corresponding motion is discussed. Frequencies, winding numbers, and the location of resonances are also determined. The results may serve as a basis for perturbation theory of slightly modified systems, and for semi-classical quantization.
EPR of VO2+ in ZnTiF6 · 6H2O
Authors: Jayaram Geetha , Krishnan V. G.
Published: February 2015

Electron Paramagnetic Resonance (EPR) studies have been carried out on the vanadyl (VO2) ion doped in single crystals of ZnTiF6 • 6H2O. The spectra indicate the presence of one set of eight lines characteristic of only one occupation site. The V-O bond orientation is along one of the three Zn-H2O bond directions in the trigonally distorted [Zn(H2O)6] octahedra. This behaviour is unlike that reported for vanadyl ion substituting for the M(H2O)6 sites in the Tutton salts, alums and AlCl3 • 6H2O. The Spin-Hamiltonian and bonding parameters for the [VO(H2O)5] complex have been evaluated. The hyperfine linewidths are 0.8 mT at 300 K and 77 K. No proton superhyperfine structure was observed at both these temperatures.
Calculation of the Partition Function of a Double Minimum Oscillator from a Modified Variation Perturbation Method
Authors: Taubmann Gerhard
Published: February 2015

The partition function of a double minimum oscillator is evaluated by means of variation perturbation theory. For low temperatures, the method cannot be applied in the usual way. Even for a symmetric double minimum potential VDM(x), the shift of the harmonic reference oscillator is not always zero as expected, but its minimum is near one of the minima of VDM(x) at low temperatures. The partition function thus calculated is only half the correct value. For sufficiently high temperature, the method works normally. The anomaly in the low temperature region is investigated in detail, and a modification of the variation perturbation method is suggested which eliminates most of the problems.
Die Lösung der Schrödinger-Gleichung als eindimensionales Problem. III. Einelektronsysteme mit verbesserten Diskretisierungsmethoden
Authors: Preuß H. , Pernpointner M.
Published: February 2015

After the calculations on one-electron atoms with simple discretization methods in part II of this work, more powerful techniques are presented here. The method of ARICKX was transferred to our one-dimensional calculations, and a fast „energy profile method" is used with which the excited states of one-electron atoms can be reproduced with high accuracy. The simplest polyatomic particle, H+
2, can be integrated into the formalism without any difficulties because of the general applicability of the integral kernel. Good results are available for this system, and a geometry optimization yields the same core distance as given in the literature.
Structural and Defect Study of LiMn2O4 Formation
Authors: Massarotti V. , Bini M. , Capsoni D.
Published: February 2015

The LiMn2O4 formation from MnO and Li2CO3 mixtures with lithium cationic fraction 0.31 <̲ x <̲ 0.40 was studied by structural profile refinement from X-ray data, thermal (TGA and DSC) measurements and scanning electron microscopy (SEM) observations. Quantitative phase analysis, structural and microstructural parameters and composition of the coexisting phases were obtained. Different behaviours were observed in the composition ranges 0.33 <̲ x <̲ 0.35 and x >̲ 0.37. In the former range only the stoichiometric spinel phase was obtained, in the latter, in addition to the Li2MnO3 compound, two spinel phases could be considered: I) LiMn2O4 stoichiometric spinel; II) Li1 + yMn2-yO4 (0.11 <̲ y <̲ 0.23), a non-stoichiometric phase whose small particle size resulted practically independent of the initial composition and annealing temperature. Such a conclusion was supported also by SEM observations. The relative abundance of phase II increased with increasing lithium content and with decreasing temperature.
Relaxation of 27Al NMR in Aluminium Tribromide due to Raman Process
Authors: Okubo Noriaki , Igarashi Mutsuo , Yoshizaki Ryozo
Published: February 2015

The nuclear spin-lattice relaxation of 27Al NMR in AlBr3 has been examined from 25 to 320 K. The result is analyzed using a theory of the Raman process based on covalency. A Debye temper-ature of 118 K is obtained together with a covalency larger than that obtained from the relaxation in the 81Br NQR.