bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Electric Quadrupole Moment, Magnetic Susceptibility Tensor and Deuterium Quadrupole Coupling Constant in Cyanoacetylene
Authors: Stolze W. H. , Sutter D. H.
Published: February 2015

The rotational Zeeman effect in the J → J′ = 0 → 1 and 1 → 2 rotational transitions has been observed for H-C≡C-C≡14N, D-C≡C-C≡14N, D-C≡C-C=15N, and H-C≡C-C=I5N using a microwave bridge superheterodyne spectrometer. From the experimental g⊥-values, susceptibility anisotropies and rotational constants, the molecular electric quadrunole moment, which plays an important role for collisional excitation and relaxation, follows as Q∥=2.14(9) x 10-26esu cm2 (referred to the center of mass of the H-C≡C-C≡14N species).

Since the Deuterium quadrupole hyperfine splittings in the Zeeman spectra could be resolved, it was also possible to Fit the Deuterium quadrupole coupling constant. Our value, eqQ (2H) = 198.2(46) kHz is about 10% smaller than the value derived from a recent high resolution microwave Fourier transform study. The reasons for this discrepancy are discussed.

All experimental molecular parameters are compared to the results of ab initio quantum chemical calculations and it is argued that the 14N nuclear electric quadrupole moment is possibly about 30% larger than presently assumed.
Emission Continua in M + M Collisions (M = Zn, Cd)
Authors: Kowalski Andrzej
Published: February 2015

Strong UV and weak visible continua of Zn2. Cd2 and ZnCd have been observed in emission when a discharge-excited atomic beam of zinc or cadmium is crossed with an unexcited beam of zinc or cadmium. It has been found that the discharge-excited beams of Zn and Cd contain also atoms in autoionizing states with lifetimes equal to (140 ± 30) and (110 ± 20) μsec, respectively.
Correlation of Zero Field Splittings and Site Distortions. VII. FeCl4
- in CsGaCL4 with Crystal Structure Refinement
Authors: Büscher R. , Lehmann G. , Henkel G. , Krebs B.
Published: February 2015

A crystal structure refinement for CsGaCl4 resulted in considerably lower limits of error than older data from the literature. These were used for a superposition analysis of EPR data for Fe3+ in this compound. The experimental zero field splitting (ZFS) pattern could be very satisfactorily reproduced with the intrinsic ZFS parameter b̅2 = 0.6 cm-1. Thus like for other ligands b̅2 for Fe3+ is again several times larger than for the isoelectronic Mn2+ .
CI Calculations of X-ray Scattering Intensities for some Linear Molecules [l]
Authors: Breitenstein Martin , Meyer Hermann , Schweig Armin
Published: February 2015

X-ray scattering intensities for molecular gases have been calculated in the first Born approximation using correlated ab initio wavefunctions. The influence of electron correlation has systematically been studied for the series of molecules C2H2, CO, N2, O2 and F2. The correlation effects turn out to be very pronounced for the total and inelastic scattering and less so for the elastic scattering (where they cannot be neglected, however). Hopes are raised that the timely results will stimulate progress in the very recent research topic of gas X-ray diffraction.
High Resolution Transmission Electron Microscopy of Some Catalysts
Authors: Qiao G. W. , Zhou J. , Kuo K. H.
Published: February 2015

Application of high resolution electron microscopy (HREM) to the study of Pt-Sn/γ-Al2O3 supported catalyst, zeolites, iron catalyst for ammonia synthesis, rare-earth oxide catalysts, etc., is described. Micro-twins, dislocations and other crystallographic imperfections are observed. Moreover, the structure images of channels representing columns of cages in several kinds of zeolites as well as radiation damage processes in them have been recorded in situ. The observed images of zeolites were found to be in good agreement with the structure model projections and computer simulated images.
MCSCF-CI Calculations of Radiative Transition Probabilities of PH and PD
Authors: Senekowitsch J. , Rosmus P. , Wemer H. J. , Larsson M.
Published: February 2015

Potential energy, dipole moment, and electronic transition moment functions for the A 3Πand X3Σ- states of PH have been calculated from highly correlated electronic wavefunctions. The electric dipole moments in the vibrational ground state of PH are calculated to be 0.637 Debye (A 3Π) and 0.403 Debye (X3Σ-). The predicted rates of spontaneous emission between low lying vibrational states of the X state lie in the range of 46 to 109 sec-1 (PH) and 12 to 30 sec-1 (PD). The calculated radiative lifetime of the v' = 0 level in the A 3Π state of 400 ns is lower by about 10 percent than the most recent experimental value. The classical intersection of the 5Σ- and the A 3Πstate has been calculated to lie between v' = 2 and 3 with an expected uncertainty of about 500 cm−1, whereas the onset of the rotationally dependent predissociation lies at v' = 0, J' = 11.
On the Hyperpolarizability of the Lithium Dimer
Authors: Maroulis George
Published: February 2015

All independent components of all electric polarizability and hyperpolarizability tensors up to the fourth rank have been calculated near the Hartree-Fock limit for Li2(l σg
2 1 σu
2 2 σg
2 X1 Σg
+). Many of the molecular properties reported in this paper appear for the first time in the literature. Our values for the isotropic components of the C, B and γ hyperpolarizabilities are 1487 e2 a0
4Eh
−1, −490 x 102e3 a0
4Eh
−2 and 510.5 x 103 e4 a0
4 Eh
−3 respectively.
Notizen: Temperature Measurements o f Laser Heated Cavities
Authors: Herrmann P. , Pakula R. , Földes I. B. , Sigel R. , Tsakiris G. D. , Witkowski S.
Published: February 2015

Absolute soft x-ray measurements on laser heated gold cavities (0.25-1 mm diam.) yield brightness temperatures > 106 K. Comparison with theoretical work shows that the temperature in the cavity is determined by the diffusive loss of radiation into the wall.
The Structure Factor of Expanded Liquid Alkali Metals at the Long-Wavelength Limit
Authors: Khanna K. N. , Shanker G.
Published: February 2015

S (0 ) values of expanded alkali metals are calculated in random phase approximation. The results reproduce positive values of S (0) at sufficiently high temperatures showing the validity of RPA in one-component plasma systems.
The Microwave Ground State Spectra of Methylphosphine-Borane-(11B) and Methylphosphine-Trideuteroborane-(11B)
Authors: Kasten W. , Dreizler H. , Kuczkowski R. L. , Soltis LaBarge M.
Published: February 2015

The microwave ground state spectra of methylphosphine-borane-(11B) and methylphosphinetrideuteroborane-(11B) have been measured by microwave Fourier transform spectroscopy and analysed for 11B-nuclear quadrupole hyperfine splittings and CH3 and BH3 torsion fine structure. As high J transitions were measured a centrifugal distortion analysis was necessary. The B-P bond order is discussed.
Elektronenspektren der Fluoro-Chloro-Osmate(IV), [OsFnCl6–n]2-,n = 0– 6
Authors: Preetz W. , Ruf D.
Published: February 2015

The electronic absorption spectra of the solid tetraalkylammonium salts of [OsFnCl6-n]2-, n = 0 -6 , including the stereoisomers for n = 2, 3, 4, are measured at 10 K. The strong bands in the UV/VIS region are assigned to charge-transfer transitions from π(t1 u, t2 u) and σ (t1 u) Cl orbitals into the π (t2g
4) Os(IV) level. The observed splittings and shifts are interpreted by qualitative MO treatment according to point groups D 4h, C4v, C 3v and C 2v of the mixed complexes. The weak intraconfigurational transitions within the t2g
4 configuration of Os(IV) are splitted by spin orbit coupling and lowered symmetry into multiplets with up to five states, observed in the NIR regions 4700-7300, 10 700-13 200 and 17 000-21 600 cm -1. The O -O - transitions are deduced from vibrational fine structure; in some cases they are confirmed by electronic Raman bands with the same frequencies and by hot bands observed in the normal temperature spectra. Within the series of complexes all absorption bands are shifted systematically to higher energies with increasing number of F-ligands.
Self-Diffusion of Sodium, Chloride and Iodide Ions in Methanol-Water Mixture
Authors: Hawlicka E.
Published: February 2015

The self-diffusion coefficients of Na+, Cl- and I- in methanol-water solutions at 35 ± 0.01 °C have been measured in their dependence on the salt molarity in the range 1 · 10-4- 1 · 10-2 mol dm -3. The ionic self-diffusion coefficients in infinitely diluted solutions have been computed. The influence of the solvent composition on the solvation of the ions is discussed. A preferential hydration of Na+, Cl- and I- ions in water-methanol mixtures has been found.
In-situ X-Ray Small Angle Scattering during the Crystallization of Amorphous Mg76Zn24
Authors: Schaal M. , Lamparter P. , Steeb S.
Published: February 2015

By X-Ray small angle scattering the relaxation and crystallization of amorphous Mg76Zn24 was investigated in-situ. Radii of gyration of the different phases developing during the annealing of the sample were determined. By comparison of the small angle scattering results with DSC-results from the literature and the phase diagram the different phases could be identified. The crystallization of amorphous Mg76Zn24 is preceded by the formation of β-phase (Mg72Zn28)-like inhomogeneities in the amorphous phase. Further annealing leads to the final crystalline phases γ-MgZn and Mg.
Temperature Dependent Sign Reversal of the Optical Anisotropy in Pyramidic Mesophases
Authors: Zimmermann H. , Poupko R. , Luz Z. , Billard J.
Published: February 2015

Hexasubstituted tribenzocyclononene derivatives with R = -OC(O)C6H4CnH2n+i and R = -OC(O)C6H4OCnH2n+1 possess enantiotropic pyramidic mesophases. These mesophases exhibit an uncommon feature in that their optical anisotropy changes sign as function of temperature within the mesophase region. It is suggested that this effect reflects conformational changes involving the side chain benzene ring.
Nuclear Quadrupolar Relaxation m Liquid Alloys and Nearest Neighbour Dynamics
Authors: Maxim P. , Brinkmann R. , Paulick C. A. , Elwenspoek M. , Hartrott M. v. , Kiehl M. , Quitmann D.
Published: February 2015

A theory of the quadrupolar relaxation rate,

RQ , for ideal liquid binary metallic mixtures is
presented. The theory predicts cancellation after a few tenths of a picosecond of the two and
three particle correlation terms in the fluctuation of the electric field gradient (EFG) for pure
metals, and prevailing of the three particle term for binary mixtures. This is due to the high
symmetry in the arrangement of the atoms around a probe nucleus. The prevailing of the three
particle term in binary systems leads to a longer correlation time (a few picoseconds) of the
fluctuating EFG and explains the experimentally observed higher values of RQ and their
quadratic concentration dependence. The validity of the theory has been confirmed by experimental
data. Deviations for some real systems are discussed.
Boron, Nitrogen, and Fluorine Nuclear Quadrupole Coupling and the Electronic Structure of the Boron—Nitrogen Single Bond
Authors: Olliges J. , Lötz A. , Voitländer J. , Barfuss H. , Böhnlein G. , Gubitz F. , Ittner W. , Lanzendorfer G. , Kreische W. , Röseler B.
Published: February 2015

The 11B and 19F nuclear quadrupole couplings in F3BNHx(CH3)3-x compounds are reported. The boron quadrupole couplings were measured by quadrupole perturbed NMR in the solid state. The fluorine quadrupole couplings were obtained by the time-differential observation of the angular distribution of the gamma radiation after excitation of the fluorine nuclei with accelerated protons (TDPAD). The results are discussed in connection with the nitrogen quadrupole couplings in F3BNHxR3-x compounds, and the nitrogen and boron quadrupole couplings in H3BNHxR3-x: compounds which were previously determined by nuclear quadrupole double resonance. In the F3BNHxR3-x series of compounds, the donor-acceptor character of the B -N bond appears to be less im portant than in the H3BNHxR3-x compounds in favour of a more ionic character of the bond with a higher negative charge on nitrogen.
Pressure Dependence of the Proton Transfer Equilibrium in Hydrogen Bonded Complexes
Authors: Maćkowiak Mariusz , Kozioł Piotr , Stankowski Jan
Published: February 2015

35Cl NQR measurements were carried out on complexes of pentachlorophenol with nitrogen bases as a function of pressure (up to 300 MPa) and of temperature. It is shown that the sign and magnitude of the pressure coefficient of the 35Cl NQR frequency is related to the degree of proton transfer. An anomaly in the pressure coefficient of ν (35Cl) has been observed near 50% of the proton transfer in the hydrogen bond. This anomaly is discussed assuming that the proton transfer equilibrium is pressure dependent. The fact that the transition from the double-well potential of the hydrogen bond to the single-well potential occurs in the critical manner is also taken into account.
Electric Field Gradient Modulation in Incommensurate Systems X2YZ4
Authors: Pirnat J. , Lužnik J. , Trontelj Z.
Published: February 2015

The subject of the paper is the plane wave limit of static incommensurate displacement modulation in the crystal structure, which is related to the commensurate ferrophase modulation. Using the point charge model, the corresponding electric field gradient modulation and quadrupole perturbed NMR spectra are calculated. The corrections up to the 4th order owing to the incoherent displacements of the charges in the vicinity of the resonant nucleus are considered. Comparison with the experimental data shows a reasonable agreement.
14N Electric Field Gradient Tensors in Incommensurate [N(CH3)4]2ZnCl4
Authors: Dolinšek J. , Blinc R.
Published: February 2015

The 14N electric field gradient tensors have been determined in the paraelectric phase at T = 26 °C and in the incommensurate phase at T = 16 °C. The results in the incommensurate phase are typical for the “non-local” case and show the presence of two out of phase components of the modulation wave. The phase shift between the linear and the quadratic terms in the expansion of the frequency in powers of the order parameter is as large as 45°.
Low Temperature Phase of NaOD
Authors: Bastow T. J. , Amm D. T. , Segel S. W. , Heyding R. D.
Published: February 2015

The existence of a new phase of NaOD below 160 K is reported. NQR, NMR and DTA spectra are given and preliminary X-ray powder diffraction measurements are discussed.
Kathodolumineszenz der Seltenerd-aktivierten Granate Gd3Te2Li3O12 und Y3Te2Li3O12
Authors: Otto R. , Kemmler-Sack S.
Published: February 2015

By activation of the host Gd3Te2Li3O12 with the trivalent rare earth ions Ln3+ = Pr, Sm, Eu, Tb-Tm and of Y3Te2Li3O12 with Ln3+ = Pr, Eu, Tb a cathodoluminescence in the visible region is obtained. The influence of the electronic structure and concentration of the activator on the relative emission efficiency as well as the host lattice participation in the energy transfer processes are discussed.
Schwingungsspektren und Normalkoordinatenanalyse des P2Se6
4–-Anions in den konformeren staggered- und eclipsed-Anordnungen in TL4P2Se6und Na4P2Se6
Authors: Parensen M. , Brockner W.
Published: February 2015

Na4P2Se6 has been prepared by elemental synthesis at high temperatures and characterized by vibrational spectroscopy. The vibrational frequencies of Na4P2Se6 are assigned on the basis of eclipsed P2Se6
4- conformers with D3h symmetry, those of Tl4P2Se6 on the basis of staggered P2Se6
4- units with D3d symmetry. A normal coordinate analysis has been performed for both conformers. The refined force field, potential energy distribution (PED), mean amplitudes of vibration an Coriolis coupling constants are given.
Electrochemical Investigation of the Ternary Phase Diagram Lithium-Indium-Antimony at 400 °C
Authors: Sitte W. , Weppner W.
Published: February 2015

The phase diagram of the ternary system Li-In-Sb is determined at 400 °C by electrochemical techniques. The lithium content of samples with different In : Sb ratios is varied by coulometric titration. The equilibrium lithium activities are obtained from emf measurements. Two new ternary compounds, Li3InSb2 and Li6InSb3 with a wide range of stoichiometry, exist along the quasibinary cut InSb-Li3Sb. Both compounds are in equilibrium with In and Sb. Li3Sb co-exists with all Li-In phases. Semiconducting phases of narrow ranges of stoichiometry show generally fast chemical diffusion rates. The In rich phases have large stoichiometric widths and equilibrate much more slowly.
Neutron- and X-ray-Diffraction Study on the Structure of Amorphous Co25Ti75
Authors: Müller A. , Bühler E. , Lamparter P. , Steeb S.
Published: February 2015

Amorphous Co25Ti75 could be produced using the melt-spin-technique. A neutron- and a X-ray-diffraction experiment was performed. Assuming SNC ≡ 0 the partial Bhatia Thornton structure factors SNN and SCC as well as the partial coordination numbers were calculated. The discussion yields the atomic distances and the chemical short range order parameters.
Finite Amplitude Convection in a Rotating Porous Medium
Authors: Dandapat B. S.
Published: February 2015

The onset of convection in a horizontal layer of a saturated porous medium heated from below and rotating about a vertical axis with uniform angular velocity is investigated. It is shown that when S ∈ σ >1, overstability cannot occur, where ε is the porosity, σ the Prandtl number and S is related to the heat capacities of the solid and the interstitial fluid. It is also shown that for small values of the rotation parameter T1, finite amplitude motion with subcritical values of Rayleigh number R (i.e. R < Re, where Re is the critical Rayleigh number according to linear stability theory) is possible. For large values of T1, overstability is the preferred mode.
A Molecular Dynamics Study of the Structure of an LiCl • 3 H2O Solution
Authors: Tanaka K. , Ogita N. , Tamura Y. , Okada I. , Ohtaki H. , Pálinkás G. , Spohr E. , Heinzinger K.
Published: February 2015

The structure of an 18.5 molal aqueous LiCl solution has been investigated by MD simulation. The total radial distribution function from the simulation agrees reasonably well with that of an X-ray diffraction measurement. In the average each Li+ is in contact with one Cl-. Additionally, there are four water molecules in the first coordination sphere of Li+ which occupy preferentially octahedral positions. The hydration shell of Cl- is strongly disturbed by the formation of the contact ion pair. There is an almost complete breakdown of the water structure although the number of nearest neighbours is still four at the normal O - O distance in water. For the C1--C1- radial distribution a strong discrepancy exists between a neutron diffraction study with chloride isotope substitution and the simulation. All results are compared in detail whit recently published data from a simulation of a 13.9 molal LiCl solution.
Anomalous Temperature Dependence of the 127I Quadrupole Interaction in Tetraethylstiboniummetaperiodate (C2H5)4SbIO4
Authors: Klobasa Dagmar G. , Burkert Paul K.
Published: February 2015

127I solid state NMR studies revealed second order quadrupole effects in (C2H5)4SbIO4 with anomalous positive temperature coefficients of the quadrupole coupling constants. This anomaly is caused by a continuous change of the axes of the electric field gradient tensor.
Different Types of Current Instabilities During Low-Temperature Avalanche Breakdown of p-Germanium
Authors: Peinke J. , Parisi J. , Mühlbach A. , Huebener R. P.
Published: February 2015

The highly nonlinear current transport behavior of extrinsic germanium, electrically driven into distinct parameter regimes of impact-ionization-induced avalanche breakdown at liquidhelium temperatures, shows a variety of temporally unstable dissipative structures. We have observed experimentally three different types of current instabilities.
Density Polarization and Chemical Reactivity
Authors: Nalewajski Roman F. , Koniński Marek
Published: February 2015

A qualitative analysis of the main polarization effects in molecular systems is presented. Both the single and multiple site reactivity cases are discussed and illustrative applications are given for selected molecular systems: acrylonitrile, propene, formamide, and the trans-nitrous acid. The polarization effects are expected to determine the directional specificity of an early approach (before the substantial charge transfer and the intramolecular rearrangements) of both reactants in a chemical reaction. The preferred direction of such an approach is therefore postulated as that generating the minimum energy change of reactants in the Field of their respective reaction partners, including the stabilization due to the relaxation of their densities in a changed environment. The example of the electrophilic substitution in the five membered heterocycles is examined. It demonstrates the importance of the density polarization effects for explaining the observed α-preference in these reactions for furan, pyrrole and N-methyl pyrrole. Next we discuss the relation between the density relaxation and the internal stability of molecular systems. Finally, we briefly comment on the Atoms-in-a-Molecule description.
Thermodynamics of the Ternary System Na2O—P2O5 —B2O3
Authors: Julsrud S. , Kleppa O. J.
Published: February 2015

The enthalpies of mixing of the liquid mixtures of (NaBO2)2 + B2O3 , Na4P2O7 + (NaPO3)2 , (NaPO3)2 + B2O3 and Na4P2O7 + (NaBO2)2 have been measured by liquid + liquid calorimetry. The results are discussed in terms of tentative structural models of the melts, and in terms of O2- ion transfers from phosphorus groups to boron groups in (NaPO3)2 + B2O3 and from boron groups to phosphorus groups in Na4P2O7 + (NaBO2)2 .
Molar Volume and Surface Tension of Molten LaCl3-KCl Mixtures
Authors: Igarashi K.
Published: February 2015

Molar volumes and surface tensions of molten LaCl3-KCl mixtures were measured by dilatometry and the maxim um bubble pressure method, respectively. The molar volume isotherms were found to deviate positively from additivity over the whole composition range, with the maxim um deviation at ca. 30 mol% LaCl3. At the same concentration the isotherms of surface tension at temperatures below 950 °C show a minimum . Surface energy of mixing per unit area calculated from the surface tensions shows a large negative excess at the corresponding composition. These observations are related to the existence o f LaCl6
3- in the KCl-rich melt.
Enumeration of Kekulé Structures for Multiple Zigzag Chains and Related Benzenoid Hydrocarbons
Authors: Cyvin S. J. , Cyvin B. N.
Published: February 2015

The benzenoid classes of multiple zigzag chains, A (n, m ), and incomplete multiple zigzag chains. A (n, m, l), are considered. Numerical numbers of Kekulé structures (K ) are given for n up to 5 and m up to 10. A recurrence relation is developed for the K numbers of A(n, m) with fixed values of n; a general formulation for arbitrary m values was achieved.

Six new benzenoid classes are studied in connection with the application of the John-Sachs theorem to double zigzag chains. A new approach to the K enumeration is introduced by nonlinearly dependent recurrence relations.

Finally a new type of combinatorial K formulas in terms of determinants and based on the John-Sachs theorem , is introduced. The new enumeration techniques are applied to multiple zigzag chains.
Assessment of the Accuracy of the Quasiclassical Trajectories Approximation at a Low Collision Energy for the He — N2 System
Authors: Metropoulos Aristophanes
Published: February 2015

We have computed rotational energy transfer differential and state-to-state integral quasiclassical cross sections for the He - N2 system at 27.3 meV. By comparing these differential cross sections to close coupling ones, the accuracy of the quasiclassical approximation at such a low collision energy has been assessed as satisfactory.
Chemical Hardness and L. Pauling’s Scale of Electronegativity
Authors: Komorowski Ludwik
Published: February 2015

The energy of the charge transfer interaction is expressed using absolute electronegativities and hardness parameters. The master equation appears to bind together Pauling and Mulliken scales by the factor (7/4 π ε0)1/2 = 3.174 V1/2 nm1/2 electron-1/2. An index of charge transfer affinity (CTA) is proposed as possible measure of the tendency to ionic bonding between atoms.
A Calibrated Large-area X-Ray Source for Plasma Spectroscopy
Authors: Morsi H. W. , Röhr H. , Schumacher U.
Published: February 2015

A large-area (10 x 30 cm2) X -ray source for relative and absolute calibration of double-crystal monochromators for plasma soft X -ray spectroscopy was developed. For a voltage of 20 kV and a current of 1 mA uniform and reproducible emission is achieved at a level of about 30 mW /(m2 · sr) for Kx, line emission in the photon energy range from 1 keV to about 8 keV, while the Lx line emission increases with photon energy from 10 to 20 m W/(m2 · sr).
Toroidal Helical Fields
Authors: Kucinski M. Y. , Caldas I. L.
Published: February 2015

Using the conventional toroidal coordinate system Laplace’s equation for the magnetic scalar potential due to toroidal helical currents is solved. The potential is written as a sum of an infinite series of functions. Each partial sum represents the potential within some accuracy. The effect of the winding law is analysed in the case of small curvature. Approximate magnetic surfaces formed by toroidal helical currents flowing around a standard tokamak chamber are determined. Stability of the plasma column in this system against displacements is discussed.
Rotational Dependence of the Unimolecular Decay Rate: Benzene Cation Dissociation
Authors: Kiermeier A. , Neusser H. J. , Schlag E.W.
Published: February 2015

We present the first example of unimolecular decay rates of a polyatomic system in which reactants are rotational state selected. Highly excited, but internal energy selected and J rotational quantum number selected benzene cations are produced in a two laser pump-pump experiment. Slow reactive decay of these ions is observed in a reflectron time-of-flight mass spectrometer and the total decay rate constant k(E, J ) is measured as a function of J. At constant internal energy E, k(E, J) decreases with increasing J.
Experimental Investigation of Spatial Pattern Formation in Physical Systems of Activator Inhibitor Type
Authors: Purwins Hans-Georg , Radehaus Christian , Berkemeier Jürgen
Published: February 2015

We investigate experimentally stationary stable states of activator (w) inhibitor (υ) type systems corresponding to the reaction diffusion equation

δ · υ̇ = Δυ + w - υ; ẇ = σ Δw + f(w) - υ; δ, σ = const > 0

with f(w) monotonically increasing for small and decreasing for large |w|. We first describe some general mathematical properties and present qualitative results obtained from numerical calculations. We then investigate experimentally electrical networks described by the spatially discretized version of the above equation. Calculation and experiment are in good agreement. We also interprete a two dimensional-network as an equivalent circuit for a composite material consisting of a linear and a nonlinear layer with an s-shaped current density electric field characteristic. This model is used for a phenomenological description of spatial structures and global current voltage characteristics observed experimentally in pin-diode like and gas discharge devices. The model accounts very well for the experimental results obtained so far. It is concluded that the above equation and the corresponding experimental setup are of great interest for fundamental investigations of self con­trolled processes in nature.
Molecular Polarity and the Structure of Liquid Methanol
Authors: Pálinkás G. , Tamura Y. , Spohr E. , Heinzinger K.
Published: February 2015

The structure of liquid methanol as a function of the molecular polarity has been studied by MD simulations. The results obtained by scaling the partial Coulombic charges located at the molecular interaction sites show that the polar forces leading to the hydrogen bonding phenomena also influence the relative orientation of nearest neighbor molecules and thus their local packing. It is shown that hydrogen bonding in liquid methanol contributes considerably to the X-ray structure function. The changes with polarity of the pair interaction energy distributions, the intramolecular geometry, and the vibrational frequencies are reported. The results are compared with those obtai­ned from RISM calculations.
Rotational Tunnelling of CD3Groups in Molecular Crystals as Studied by NMR Spectra
Authors: Lalowicz Z. T. , Werner Ulrike , Müller-Warmuth W.
Published: February 2015

Tunnelling frequencies of rotating CD3 groups in solids between about 20 kHz and 2 MHz may be obtained from the 2H NMR spectra. The theory of the spectral response is developed where quadrupole and dipole-dipole interactions as well as rotational tunnelling are taken into account. Features characteristic of tunnelling, which distinguish the spectra from those of rapidly reorienting deuterated methyl groups, are found from analytically calculated spectra even for the case of very large tunnel splittings. Numerical calculations have been performed for various conditions to deter­ mine the tunnel frequency. Experimental spectra measured at 45 MHz and low temperatures have revealed the appearance of rotational tunnelling in CD3I, CD3COONa, and (CD3COO)2Cu • H2O. In the latter case, a tunnelling frequency of 608 kHz has been extracted from the spectrum at 27 K.
Quadrupole Hyperfine Structure in the Rotational Spectrum of n-PropylIsocyanide
Authors: Vormann K. , Schwarz R. , Dreizler H.
Published: February 2015

An investigation of the 14N quadrupole hyperfine structure in the rotational spectrum of n-propyl isocyanide is presented. It was possible to resolve the multiplets by using microwave Fourier transform spectroscopy.
Study of T1-and T2-Relaxation by Microwave Pulse Techniques: Rotational Transition J=0-1 of HCCF,J-Dependence of Rotational Transitions of S02,and l-Type Doublet Transitions of HC15N Perturbed by Self, H2, D2, and He
Authors: Mehrotra S. C. , Mäder H.
Published: February 2015

With a K-band bridge type superhet spectrometer, the pressure dependence of the population decay rate 1/T1 by using a (π τ π/2) pulse technique, and of the coherence decay rate 1 /T2 by using a π/2-pulse technique, have been determined for the following systems at room temperature: (a) rotational transition J = 0-1 of fluoroacetylene (HCCF), (b) seven rotational transitions of sulfur dioxide (S02) with 5 ≦J ≦37, both (a) and (b) with pure gases, and (c) l-type doublet transitions of hydrogen cyanide (HC15N) in the (0110) vibrational state with J = 9 and 10 using HC15N, H2, D2 and He as perturbers. A theoretical treatment of Bloch-type equations with a special attention to the M-degeneracy of the energy levels is also considered to describe the microwave pulse experiments. For systems (b) and (c), the values of 1/T1 are found to be significantly smaller than corresponding values of 1/T2, indicating adiabatic collisions as a dominant mechanism for the decay of sample coherence. For the system (a), the value of 1/T1 is found to be slightly greater than the corresponding value of 1/T2. The normalized perturbative collision theory proposed earlier has been applied to explain the results of systems (a) and (c). The unsatisfactory agreement between theory and experiment for the system (c) indicates that a nonperturbative approach or a higher order perturbation treatment should be taken into consideration for a better description of collision dynamics.
A Theoretical Study of Fulvene Radical Cations
Authors: Khalil Salim M.
Published: February 2015

MINDO-Forces calculations have been performed, after complete optimization of geometry, on fulvene molecule, fulvene and X-fulvene radical cations, where X is OH, NH2, CH3, NO2, CN and F. A twisted structure with angle 5° was found for fulvene radical cation. The substituents OH, NH2, CH3, CN and F are stabilizing. NO2 is slightly stabilizing. Geometrical parameters, heats of formation, dipole moments and electron densities are reported.
Schwingungsberechnungen des Hexathiometadiphosphatanions P2S6
2-
Authors: Ohse Lothar , Brockner Wolfgang
Published: February 2015

A normal coordinate analysis for the Hexathiometadiphosphate anion P2S6
2- was performed, based on a simple initial force field. The force field was refined by adjusting the symmetry force constants to approximate the observed frequencies. The final force field, potential energy distribution (PED) and mean amplitudes of vibration are also given. Based on the normal coordinate analysis a new assignment of the P2S6
2- frequencies is proposed.
2H NMR Patterns of Methylaromatics Adsorbed on Graphite
Authors: Boddenberg B. , Große R.
Published: February 2015

2H NMR solid state powder patterns were measured at one monolayer coverage of benzene on the non graphitized carbon black Spheron, and of toluene, p-xylene, mesitylene, and mellitene (hexamethylbenzene) on the graphitized carbon black Graphon. Benzene on Spheron, in contrast to Graphon, exhibits a typical Pake type powder pattern shape demonstrating the minor influence of paramagnetic centers on the pattern shapes as well as confirming the formerly introduced shielding anisotropy interaction in the case of graphite. From the highly asymmetric appearance of the 2H powder patterns for the adsorbed methyl-aromatics on Graphon the flat orientation of these molecules on graphite as well as details of the rotational molecular motions are deduced.
Structural Study for a New Superconducting Phase in the Bi-Sr-Cu -O System
Authors: Sugiyama Kazumasa , Waseda Yoshio , Moroishi Keiji , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2015

A structural identification of the superconducting phase in the Bi-Sr-Cu-O system has been carried out by X-ray and electron diffraction. A lamellar oxide structure expressed by the formula Bi2(Bi, Sr)2CuOx with the orthorhombic a = 0.537 nm, b ≃ 5 · 0.537 nm and c = 2.463 nm (pseudotetragonal subcell a = 0.5369 (1) nm and c = 2.4627(5) nm) is found to be responsible for the superconductive property. The structural model of this compound is compared with the Aurivillius phases.
The Viscosity Coefficients of Oriented Nematic and Nematic Discotic Liquid Crystals; Affine Transformation Model
Authors: Baalss D. , Hess S.
Published: February 2015

General expressions are derived for the anisotropy of the viscosity and for the Leslie coefficients governing the flow alignment subject to the assumption that the equipotential surfaces for the interaction of oriented nonspherical molecules in the nematic or nematic discotic phase of a liquid crystal are related to a spherical interaction potential by an affine transformation. In particular, for uniaxial particles, the seven independent viscosity coefficients of a nematic are given in terms of the two viscosity coefficients of a reference fluid of spherical particles and the axes ratio of the nonsphe­rical molecules. The theory is compared with results from nonequilibrium molecular dynamics computer simulations and with experimental data.
Ramanujan and the Julia Set of the Iterated Exponential Map
Authors: Lakhtakia Akhlesh , Lakhtakia Mercedes N.
Published: February 2015

The Julia set of Ramanujan's iterated exponential map, Fr+1(z) = exp {Fr(z)} -1, is investigated for positive integral r. Connection with Devaney's work on the map zr+1 = λ exp[zr] is also made.
79Br, 127I NQR of Diammoniumalkyl Halides and Piperazinium Halides. Crystal Structure of Piperazinium Dibromide Monohydrate and Piperazinium Monoiodide
Authors: Hartmann Jutta , Dou Shi-Qi , Weiss Alarich
Published: February 2015

The 79Br and 127I NQR spectra were investigated for 1,2-diammoniumethane dibromide, -diiodide, 1,3-diammoniumpropane dibromide, -diiodide, piperazinium dibromide monohydrate, and piperazinium monoiodide in the temperature range 77 ≦ T/K ≦ 420. Phase transitions could be observed for the three iodides. The temperatures for the phase transitions are: 400 K and 404 K for 1,2-diammoniumethane diiodide, 366 K for 1,3-diammoniumpropane diiodide, and 196 K for piperazinium monoiodide.

The crystal structures were determined for the piperazinium compounds. Piperazinium dibromide monohydrate crystallizes monoclinic, space group C2/c, with a= 1148.7 pm, 0 = 590.5 pm, c= 1501.6pm, β = 118.18°, and Z = 4. For piperazinium monoiodide the orthorhombic space group Pmn 21 was found with a = 958.1 pm, b = 776.9 pm, c = 989.3 pm, Z = 4. Hydrogen bonds N - H ... X with X = Br, I were compared with literature data.
Line Spectrum Emission of Eu-Activated ZnS
Authors: Kynev K. , Kuk V.
Published: February 2015

It is shown that a ZnS:Eu phosphor with line emission spectrum can be prepared without coactivator introduction, contrary to previous results. The broad-band emission established in ZnS: Eu, Li is ascribed to the formation of Eu2+ centres due to the removal of lattice stress by lithium incorporation.
Lattice Vibrations of the Cooperites PdO and PtS
Authors: Kliche G.
Published: February 2015

The vibrational spectra of the cooperite type compounds PdO and PtS (space group P42/mmc - D4h
9, Z = 2) are analyzed. Good agreement between experimental and calculated lattice vibration frequencies is obtained using a force field which includes short-range force constants only. This demonstrates a highly covalent bonding character of the cooperites.
X -Ray Emission and X -Ray Self-Absorption in the High - Tc Superconductor YBa2Cu3O6.9 and other Copper Oxides
Authors: Burgäzy F. , Jaeger H. , Schulze K. , Lamparter P. , Steeb S.
Published: February 2015

O-Kα X-ray emission spectra of La2CuO4 and YBa2Cu3O6.9 are compared with calculated spectra. It is shown from O-Kα emission spectra of YBa2Cu3Ox with varying oxygen content (6.0 < X < 6.9) that with heating the superconducting compound (x = 6.9) oxygen atoms are removed from the Cu-O chains. A method for comparing X-ray self-absorption spectra from compounds with different concentrations of the element under consideration is presented. Cu-L selfabsorption spectra of YBa2Cu3Ox (6.0 < x < 6.9) are compared with those of Cu, Cu2O, CuO, and NaCuOn. By this comparison and from O-K., emission spectra, oxygen 2p holes are found to be present in the superconducting compound. The ionic character of the Cu-O bonds in the nonsuperconducting green phase Y2BaCuO5 is shown with O-Kα emission and Cu-L3 self-absorption spectroscopy. The energy gap of Y2BaCuO5 is found to be about 5 e V.
X -Ray Absorption Near Edge Structure (XANES) Calculations for the Amorphous Fe80B20- and Ni80B20-Alloys
Authors: Kizler P. , Lamparter P. , Steeb S.
Published: February 2015

Xanes spectra of the amorphous Fe80B20- and Ni80B20-alloys have been investigated using the electron multiple scattering theory of Durham et al. The calculations were based on several models for the structure of amorphous Fe80B20 and Ni80B20. Very good agreement between theoretical and experimental XANES curves was met. Opposite to former expectations for obtaining information on bond angles by XANES, this study shows that XANES points to more complex features of the structure than can be expressed in terms of bond angles.
MINDO/3 Investigation of the Structure of the Intramolecularly Hydrogen Bonded Enol Forms of 2 -Trifluoroacetylcycloalkanones
Authors: Ebraheem K. A. K. , Hamdi S. T. , Al-Derzi A. R.
Published: February 2015

MINDO/3 SCF-MO calculations with full geometry optimization were performed to determine the structure of the intramolecularly hydrogen bonded enol forms of 2-trifluoroacetylcycloalkanones. The presence of two stable exocyclic and endocyclic enol forms with a non-planar unsymmetric hydrogen bonded chelate ring is established. It is found that the intramolecular hydrogen bond is weaker in the exocyclic enol of 2-trifluoroacetylcyclopentanone, which showed greater deviation from planarity by ~23.8°. The geometrical features predicted by the MINDO/3 method and the calculated charge distribution are discussed and found to agree with the available experimental data on these systems. The merits and limitations of the MINDO/3 method are discussed.
Structural Phase Transitions and Ionic Motions in Pyridinium Hexachlorotellurate(IV),Hexachlorostannate(IV), and Hexabromostannate(IV) Crystals as Studied by 1H NMR
Authors: Tai Yutaka , Asaji Tetsuo , Ikeda Ryuichi , Nakamura Daiyu
Published: February 2015

The 1H NMR second moment M2 and the spin-lattice relaxation time T1 are determined for pyridinium hexachlorotellurate(IV), hexachlorostannate(IV), and hexabromostannate(IV) at various temperatures above ca. 140 K. The phase transition temperatures already reported from halogen NQR experiments are determined as 272, 331, and 285 K, respectively, by differential thermal analysis (DTA). The DTA as well as differential scanning calorimetry measurements show that the above phase transitions are of second-order. For pyridinium hexachlorotellurate(IV) and hexa-bromostannate(I V), a sharp 1H T1 dip was observed at the transition temperature. This is interpreted in terms of a phenomenon related to the critical fluctuation of an order parameter. From the measurements of 1H M2, 60° two-site jumps (60° flips) around the pseudo C6 axis of the cation are suggested to occur in the high temperature phases of the complexes. Modulation of X...1H (X = CI, Br) magnetic dipolar interactions due to the reorientational motion of the complex anions is considered as a possible relaxation mechanism in the high temperature phases.
Vapor Pressure Isotope Effects in Liquidand Solid Ammonia
Authors: King Tseng-Ven , Oi Takao , Popowicz Anthony , Heinzinger Karl , Ishida Takanobu
Published: February 2015

The H/D and 14N/15N vapor pressure isotope effects in liquid and solid ammonia have been measured at temperatures between 163 K and 243 K. The isotopic vapor pressure data have been fitted to T ln (P′P) = A/T- B for the liquid/liquid, liquid/solid and solid/solid ranges of temperature. The triple points are; 195.41 K (45.49 torr) for 14NH3, 198.96 K (48.35 torr) for 14ND3, and 195.58 K (48.83 torr) for 15NH3. The isotopic difference in the vapor pressures of NH3 and ND3 at temperatures between 195.41 K and 198.96 K is nearly independent of temperature within the present experimental uncertainty. The phase ratios of the reduced partition function ratios, fliq/fgas and fsol/fgas, deduced from these results are well represented by Tin (fc/fg) = A/T-B. Molecular forces in the liquid and solid ammonias are discussed using a simple cell and a 4-molecular unit cell model, respectively. The librational motions in the liquid are almost as highly hindered as they are in the solid, but the directionality of the external forces on nitrogen atoms in liquid ammonia is not as well defined as in the solid.
Some Measurements of H/D Polarizability Isotope Effects Using Differential Refractometry
Authors: Smith Mary Foster , Hook W. Alexander Van
Published: February 2015

Refractive index differences between the H and D isomers of some common molecules in the liquid phase were measured between 404.7 and 690.0 nm. The data are combined with information on molar volume isotope effects to yield values for H/D isotope effects on the static polarizability, the vibrational contribution to the static and frequency dependent parts of the polarizability, and the H/D isotope effect on the second moment of the electronic charge distribution. The present results suffice to demonstrate the practicability of this technique to measure the components of the polarizability listed above. However for accurate resolution of the vibrational and second moment contributions, refractive index data of still greater precision will be required.
An Anomalous Isotope Effect of 235U in U(IV)-U(VI) Chemical Exchange
Authors: Fujii Y. , Nomura M. , Okamoto M. , Onitsuka H. , Kawakami F. , Takeda K.
Published: February 2015

The abundance ratios of 234U, 235U, 236U and 238U were determined by mass spectrometry on uranium samples obtained from a chromatographic uranium enrichment process based on the U(IV) - U(VI) chemical exchange reaction. According to standard theory, the elementary isotope effect in processes based on equilibrium chemical exchange is proportional to the mass difference of the isotopes. In the present work this has been confirmed for 234U, 236U and 238U. However, according to the observed data the fractionation between 234U and 235U is much smaller than the one between 235U and 236U in spite of the same mass difference in either isotopic pair. The anomaly of the fractionation is concluded to be due to the characteristics of 235U, which is the only odd mass number isotope in the present system.
Isotope Effects and Concerted Two-Hydron-Transfer between Formamidine Molecules
Authors: Svensson Peder , Bergman Nils-Åke
Published: February 2015

With the intention to assist mechanistic studies of two-hydron-transfer reactions using 1H/2H isotope effects we have carried out theoretical studies of the two-hydron-transfer reaction between formamidine molecules. The ab initio STO-3G potential energy surface has been calculated and all stationary points characterized by their force constant matrices. With this basis set the two hydrons are transferred concertedly and synchronously. The transition state (TS) has D2h symmetry. 1H/2H isotope effects were calculated using the Bebovib-IV program. Our results deviated from predictions made from common simple vibrational models. The isotope effects are dominated by the zero-pointenergy contribution. The effect due to the stretching vibrations of the initial state is to a small extent counteracted by stretching of the TS. The bending vibrations appear to play a dominant role in reducing the magnitude of the isotope effect for the two-hydron-transfer reaction to a value expected for a one-hydron-transfer reaction.
Gaussian Approach to (1+1)Dimensional Solitons at Finite Temperature
Authors: Roychoudhury Rajkumar , Sengupta Manasi
Published: February 2015

Soliton solutions at finite temperature have been studied using the Gaussian effective potential approach. A critical temperature Tc is obtained at which the soliton solutions cease to exist. The effective potential has also been calculated together with the Mass Gap equation.
Rate of the Bromous Acid-Bromide Reaction Measured in a Br2-HOBr Buffer System in Sulfuric Acid Solution
Authors: Försterling Horst-Dieter , Murányi Szilvia , Schreiber Helmut
Published: February 2015

In the Belousov-Zhabotinsky system bromine species of oxidation states - 1 to 5 are important for the start and for the inhibition of the autocatalytic reaction steps. Especially, the reaction of Br- with HBrO2 competes with the oxidation of Ce3+ by BrO2 formed from HBrO2 and HBrO3. In our investigation the reaction of Br- with HBrO2 (solvent 1 M sulfuric acid) is followed spectroscopically in a mixture of bromine and hypobromous acid, which system works as a buffer for bromide. Including experiments on the hydrolysis of Br2 and on the solubility product of AgBr in 1 M sulfuric acid solution direct information about the rate constant kl of the Br-/HBrO2 reaction is obtained (k1 = 2.5 × 106 M-2 s-1 at 20 °C and 4× 106 M-2 s-1 at 25°C, which values are valid in the range of 0.01 to 1 M sulfuric acid).
14N Nuclear Quadrupole Hyperfine Structure in the Microwave Spectrum of Methyl Azide, CH3N3
Authors: Heineking N. , Gerry M.C.L.
Published: February 2015

The 14N nuclear quadrupole hyperfine structure in the rotational spectra of three isotopic species of methyl azide, CH3
14N3, CH3
15N14N2, and CH3
14N2
15N, has been resolved using microwave Fourier transform spectroscopy. The quadrupole coupling constants of 14N at all three positions have been evaluated and are compared with those from an ab initio calculation in the literature.

Since the spectra of the substituted species have been obtained for the first time, they have provided new structural information: the rotational constants are consistent with a structure in which the NNN chain is slightly bent.
The Ground State Microwave Spectrum and Dipole Moment of 2-Isocyano-Propane
Authors: Krüger Michael , Dreizler Helmut
Published: February 2015

The ground state rotational spectrum of 2-isocyano-propane is assigned. The rotational constants and the quartic centrifugal distortion constants are determined by Microwave Fourier Transform (MWFT) Spectroscopy. The analysis of the Stark effect leads to a total dipole moment of 4.055(1) D.