bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Oxygen on the Fluorescence Quenching of Polycyclic Aromatic Hydrocarbons in Two- Component Mixtures of CCl4 with Cyclohexane, Benzene and Acetonitrile
Authors: Chojnowski Andrzej , Wiczk Wieslaw M. , Latowski Tadeusz
Published: February 2015

Fluorescence quenching of anthracene and perylene has been studied in deoxygenated and nondeoxygenated two-component mixtures of CCl4 with cyclohexane, benzene and acetonitrile. It was indicate that the dissolved oxygen only reduces the fluorescence lifetimes of the hydrocarbons, thus suppressing the efficiency of quenching
The Centrifugally Induced Pure Rotational Spectrum and the Structure of Sulfur Trioxide. A Microwave Fourier Transform Study of a Nonpolar Molecule
Authors: Meyer Volker , Sutter Dieter Hermann , Dreizler Helmut
Published: February 2015

The pure rotational spectrum of sulfur trioxide has been observed for the first time. A total of 25 high-J transitions could be assigned. The rotational constants, two quartic centrifugal distortion constants, and three sextic centrifugal distortion constants were determined as: B= 10 449.0667(23) MHz, C = 5216.0330(12) MHz, DJ = 9.2651 (18) kHz, DJK = -16.3922(18) kHz, HJ, = -8.8(34) • 10-3 Hz, HJK= -15.8(73) • 10-3 Hz, and HKJ = 34.2(73) • 10-3 Hz. An r0- and an re -structure are presented: r0= 1.4198(7) Å (calculated from B), r0 = 1.4210(7) Å (calculated from C), and re = 1.4175 Å
Photochemical and Photophysical Properties of 4- Acyl [2.2] paracyclophanes
Authors: Hopf Henning , Laue Thomas , Zander Maximilian
Published: February 2015

Photochemical and photophysical properties of 4-benzoyl[2.2]paracyclophane (3) and 4-acetyl[ 2.2]paracyclophane (5) have been studied. In contrast to benzophenone and acetophenone, respectively, the lowest triplet state of 3 and 5 is of the τ, τ*-type. 3 is photochemically reactive. Photoenolization (in solution at lower temperature) is the main reaction pathway while bond fission of an exocyclic C-C bond of the formed photoenol leading to an alkylated open-chain benzophenone derivative takes place to a minor degree. Photoenolization of 3 is the first example of this type of photochemical reaction observed with a cyclophane compound, and at the same time is a novel example of the violation of Bredt's rule. Under certain experimental conditions 3 and 5 may be usable as chiral triplet sensitizers in photochemical reactions
Neutron Diffraction Studies of Structure in Aqueous Solutions of Urea and Tetramethylammonium Chloride and in Methanol
Authors: Turner J. , Finney J. L. , Soper A. K.
Published: February 2015

Neutron diffraction measurements on aqueous 2-14 molal urea solutions have been made using nitrogen isotope substitution on the urea and hydrogen isotope substitution on the water. In addition, the hydration region of the tetramethylammonium ion in 2.0 m urea solution has been investigated by nitrogen isotope substitution on the TMA at 0.5 m and 2.0 m concentration of TMAC1. The N-water correlation functions are very similar across the concentration range, and the H-H correlation function in concentrated urea solution is little changed from that of pure water. In the TM AC1 solutions the hydration peak is unchanged by the addition of 2.0 m urea. Thus urea appears to fit into the water network without causing significant perturbation of the average water structure or of the hydration region of another solute. In addition to the study of urea we have also made preliminary measurements to test the feasibility of carbon isotope substitution in liquid methanol.
Molecular Dynamics Study of Molten Lithium Iodide
Authors: Itoh S. , Konagai M. , Takahashi K.
Published: February 2015

The structural and dynamic properties of molten lithium iodide are investigated at two pressures (334 MPa at 784 K and 1054 MPa at 915 K), using molecular dynamics simulations with Born- Mayer-Huggins type pair potentials. On increasing the pressure, the local packing of the ions changes from tetrahedral to octahedral, the self-exchange velocity in the coordination shells decreases by a factor of 0.031, DLi by a factor of 0.033 and D1 by a factor of 0.021.
Conductivities of Binary Molten Alkalihalide/Silverhalide Mixtures
Authors: Boßmann H.-P. , Richter J. , Struck N.
Published: February 2015

The electric conductivities of molten (Na, Ag)Cl, (Rb.Ag)Cl, (Na,Ag)Br, (Rb. Ag)Br, and (Cs, Ag)Br are determined as functions of composition and temperature from the melting point to 1100 K. The relation of the temperature coefficients to the phase diagram of the systems (K.Ag)Cl, (Rb. Ag)Cl, (Cs, Ag)Cl, and (Cs, Ag)I near and at the phase transition (liquid-solid) is studied. The molar conductivities and mobilities of the cations with reference to the common anion are evaluated.
Molecular Polarizabilities and Orientational Ordering of Two Mesogens
Authors: Mitra M. , Paul S. , Paul R.
Published: February 2015

The refractive indices (no, ne) and densities of two mesogens have been measured in their liquid crystalline and liquid phases. The molecular polarizabilities (xo, xe) were evaluated by Vuks' and Neugebauer's relations. The polarizabilities thus obtained are compared with those estimated from the bond polarizabilities, and the orientational order parameters, , are compared with the mean field theory of Maier and Saupe, the modified mean field theory of Humphries, James and Luckhurst. and the continuum theory suggested by T. E. Faber. We have also calculated the three order parameters (<P2), τ, σ) describing the smectic A phase following McMillan's model. Possible causes of the discrepancy are discussed.
Structure and Dynamics of NaCl in Methanol. A Molecular Dynamics Study
Authors: Marx D. , Heinzinger K. , Pálinkás G. , Bakó I.
Published: February 2015

A recently developed flexible three-site model for methanol was employed to perform a Molecular Dynamics simulation of a 0.6 molal NaCl solution. The ion-methanol and ion-ion potential functions were derived from ab initio calculations. The structural properties of the solution are discussed on the basis of radial and angular distribution functions, the orientation of the methanol molecules, and their geometrical arrangement in the solvation shells of the ions. The dynamical properties of the solution - like self-diffusion coefficients, hindered translations, librations, and internal vibrations of the methanol molecules - are calculated from various autocorrelation functions.
Boron and Nitrogen Hyperfine Structure in the Rotational Spectrum of Aminodifluoroborane
Authors: Vormann  , Dreizler Helmut
Published: February 2015

The boron and nitrogen hyperfine structure in the rotational spectra of aminodifluoroborane has been investigated and the quadrupole coupling constants of 11B and nitrogen have been determined. We get the following results for the nuclear quadrupole coupling constants: Χaa(11B) = - 1.971 (6) MHz, Xbb(11B) = 0.500(11) MHz, Xcc(11B) - 2.471 (11) MHz, and Xaa(14N) = 0.890 (5) MHz, Xbb(14N) = 2.303 (7) MHz, Xcc(14N) = - 3.193 (8) MHz. Additionally we determined rotational and centrifugal distortion constants according to Watson's A reduction.
A Molecular Beam Microwave Fourier Transform (MB-MWFT) Spectrometer with an Electric Discharge Nozzle
Authors: Grabow J.-U. , Heineking N. , Stahl W.
Published: February 2015

We report on first experiments with our pulsed molecular beam microwave Fourier transform (MB-MWFT) spectrometer using a special nozzle which allows high voltage discharges within the nozzle orifice. Under these conditions we observed low J rotational transitions in highly excited vibrational states of carbonyl sulfide and sulfur dioxide, and also rotational lines of the SO radical in the 3Σ- electronic ground state and both the vibrational ground and first excited state.
Canonical Quantization of the Classical Hamiltonian for a Relativistic Spin-0 Particle
Authors: Briegel H.-J. , Englert B.-G. , Süssmann G.
Published: February 2015

When quantizing the classical Hamiltonian H (q,p,t) = [m2c4 + (c p - e A(t,q))2]1/2 + e V(t, q), commutators of the form [f (a), g(b)], where [a,b] is not a c-number, have to be evaluated. The concept of continuously symmetrized products enables us to derive a number of statements, such as a continuity equation for the density operator δ{q(t)-x)=n(t, x), in a formally concise way. We can also show, then, that the dependence of the Hamiltonian on higher powers of the kinetic momentum destroys the relativistic invariance of the theory, even if we admit a more general coupling of the external potentials than above.
X-ray Diffraction Study of Amorphous NixZr(100-x)-Alloys Prepared by Melt-Spinning
Authors: Kuschke W.-M. , Lamparter P. , Steeb S.
Published: February 2015

Amorphous Ni-Zr-alloys can be prepared by melt-spinning within a wide range of composition. Studies by X-ray diffraction yielded structure factors, pair correlation functions, total coordination numbers and atomic distances in dependence on the nickel concentration in the range of 25 up to 45 atomic percent. The change of the total coordination number and atomic distances turned out to be linear with the composition in this range. This is in good agreement with the linear composition dependence of the superconducting transition temperature, magnetic susceptibility, crystallization temperature, and electrical resistivity in the investigated range of composition.
A Simulation System for Diffusive Oxidation of Silicon:One-Dimensional Analysis
Authors: Weinert Ulrich , Rank Ernst
Published: February 2015

Thermal oxidation of silicon is described as a three-component thermodynamic local process involving silicon, silicon oxide, and oxygen molecules. A simplified system of model equations is used to demonstrate the evoluton of the Si-SiO2 interface. For the one-dimensional case the equivalence with the model of Deal and Grove could be shown analytically. For that purpose effective interface coordinates have been introduced which establish the connection between the conventional concept of sharp interfaces and our "diffusive" interface, i.e., a transition region between pure silicon and pure silicon oxide.
The Molecular 0-Tensor, the Magnetic Susceptibility Anisotropy, and the Molecular Electric Quadrupole Moment Tensor of Monofluoroacetonitrile, a Rotational Zeeman Effect Study
Authors: Krause H. , Sutter D. H.
Published: February 2015

The rotational Zeeman effect of H2F12C12C14N was observed at fields up to 20 kG (2 Tesla). The observed vibronic ground state expectation values for the molecular ^-values, the magnetic susceptibility anisotropies and the molecular electric quadrupole moments, all referred to the molecular principal inertia axes system, are: gaa= -0.03572 (11), gbb= -0.03438 (7), gcc= -0.03988 (6). 2ξaa- ξbb - ξcc = - 14.58 (10) • 10-6 erg/(G2 mole), 2ξaa- ξbb - ξcc= 1.60 (11) • 10-6 erg/(G2 mole), Qaa= -9.13 (6) DÅ, Qbb = 4M (7) DÅ, and Qcc = 4.96 (9) DÅ, respectively. The latter are in close agreement with the results of a restricted Hartree Fock self consistent field calculation with a basis of TZVP quality, which was carried out at the partial restructure determined earlier. Therefore the RHF/TZVP-value for the second electronic moment perpendicular to the heavy atom plane, <0|Σ c2
c|0)RHF, was used as additional input to predict the molecular bulk susceptibility and the individual components of the magnetic susceptibility tensor
Chlorine NQR Spin-Lattice Relaxation and Electron Spin Dynamics in Paramagnetic [Co(H2O)6[PtCl6]
Authors: Mizuno Motohiro , Asaji Tetsuo , Tachikawa Atsushi , Nakamura Daiyu
Published: February 2015

Chlorine NQR spin-lattice relaxation times T1Q were determined for [Co(H2O)6][PtCl6] at 4.2 400 K. Above ca. 350 K, T1Q decreased rapidly showing the onset of a reorientation of [PtCl6]2-. The activation energy Ea of this reorientation was determined as 125 ± 15 kJ mol-1. With decreasing temperature, T1Q showed a maximum at ca. 250 K. Below ca. 200 K, T1Q. is governed by the magnetic dipolar interaction between chlorines and paramagnetic Co2+ ions and is inversely proportional to the electron spin correlation time τe of CO2+ . τe is shown to be determined by the electron spin-lattice relaxation time T1e and the temperature independent correlation time rs for the spin-exchange between neighbouring ions above and below ca. 50 K, respectively. The temperature dependence of T1e is explained by assuming the Orbach process with an energy gap A/k of 530 + 20 K as T1e = 5 x 10-14 exp(530/T)s. τs was estimated to be 0.9 x 10-10 s.

The temperature dependence of the ESR linewidth of Mn2+ impurities in single crystal was also measured, intending to study Co2+ spin dynamics. The limit of the ESR method is discussed by comparing the obtained results with those of the NQR method
Thermodynamic Study of Eu3+ /Eu2+ Redox Reaction in Aqueous Solutions at Elevated Temperatures and Pressures by Means of Cyclic Voltammetry
Authors: Bilal B. A.
Published: February 2015

The redox potential of the couple Eu3+/Eu2+ in aqueous NaCl, NaClO4 and Na2SO4 solutions of different ionic strength and various pH values has been determined by means of cyclic voltammetry up to 458 K and 1 kbar. In all cases reversible voltammograms were obtained. Compared to the redox potential in C1O4
- solutions of pH 2, no significant shift was observed in Cl-solutions of the same pH, whereas a drastic shift to more negative potentials in solutions of SO2-
4 and in Cl- solutions of higher pH (pH 3-5) was obtained. This indicates a negligible complexation of Eu3* by means of CP but a strong one by means of OH and SO2-
4 . An isothermal pressure increase up to 1 kbar led to a shift of only few mV more negative, indicating a small pressure dependence of the change of the partial molar volume (ΔVe1) accompanying the redox reaction, which results in this case only due to the different degrees of electrostriction. A more drastic shift of the redox potential (in the positive direction) results with increasing temperature. The isobaric temperature dependence of the redox potential is described by a two parameter equation which remains valid up to the saturation pressure at 458 K, due to the small pressure effect. ΔS and ΔH of the redox reaction has been determined
Fractionation of Oxygen Isotopes at the Faces of Smoky Quartz
Authors: Klemm A. , Banerjee A. , Hoernes S.
Published: February 2015

The 18O /16O ratio under the m- and r-faces of smoky quartz has been measured; the ratio of the growth velocities was Vm/Vr = 1/3. The obtained separation factor 1.00020 is compared with that obtained previously for amethyst (1.00043), where the ratio Vm/Vr was unity
Shock Waves produced by Impulsive Load: Equation of State Effects
Authors: Lifits S. A. , Anisimov S. I. , Meyer-ter-Vehn J.
Published: February 2015

A numerical study of the flow after impulsive load of a plane material surface is carried out. It is shown that the flow is asymptotically self-similar provided one can neglect the cold components in the equation of state. In this case the effective exponent s(t) = d l n (X s) / d ln(t), derived from the shock trajectory Xs (t) does not depend on the initial pressure pulse and approaches the exponent α of the self-similar problem for time t →∞. For equations of state containing a cold pressure term, s (t) is larger than α and changes non-monotonically with time. Some features of the flow related to the presence of cold components in pressure and internal energy are discussed.
Directions of the Electronic Absorption Transition Moments in ω-Substituted 4-Dimethylamino-trans-Styrenes
Authors: Kawski A. , Gryczynski Z. , Gryczynski I. , Kuśba J.
Published: February 2015

a)

Absorption transition moment directions of the diphenylphosphinyl (2 a) and methylsulphonyl (3 a) Absorption transition moment directions of the diphenylphosphinyl (2 and methylsulphonyl

(3 a) co-substtuted in 4-dimethylamino-trans-styrenes were determined in stretched poylvinyl alcohol

(PVA) films based on measurements of the absorption anisotropics. It has been found that the

long-wave absorption spectrum consists of two bands corresponding to differently directed transition

moments. The transition moment of the intensive long-wave *La band is lies along the long axis

of these molecules whereas that of the short-wave band is oriented at (p = 38° for 2 a and q> = 35°

for 3 a relative to the transition moment direction of the 1La band-substtuted in 4-dimethylamino-trans-styrenes were determined in stretched poylvinyl alcohol (PVA) films based on measurements of the absorption anisotropics. It has been found that the long-wave absorption spectrum consists of two bands corresponding to differently directed transition moments. The transition moment of the intensive long-wave *La band is lies along the long axis of these molecules whereas that of the short-wave band is oriented at (p = 38° for 2 a and q> = 35° for 3 a relative to the transition moment direction of the 1La band
High Resolution FTIR Study of the ν8 Band and ab initio Calculation of the Harmonic and Anharmonic Force Field of Difluoromethanimine, CF2NH
Authors: Bürger Hans , Kuna Ralf , Pawelke Gottfried , Sommer Silvia , Thiel Walter
Published: February 2015

The ν8 band of CF2NH near 830 cm-1 has been measured with a resolution of 0.003 cm-1 and rotationally analyzed. The band is unperturbed, and its rovibrational parameters are given up to fourth order. Theoretical harmonic and anharmonic force constants have been calculated at the 6-31 G **SCF level, and all vibration-rotation interaction constants αi and anharmonicity constants xij are predicted. The theoretical results are compared with the available experimental data
Flüssigkristalline aromatische Cholesterin-Derivate
Authors: Vill V. , Thiem J. , Rollin P.
Published: February 2015

Liquid Crystalline Aromatic Cholesterol Derivates

A series of aromatic cholesteryl ethers, esters, phenylcarbonates and benzylcarbonates were prepared and their liquid crystalline properties studied. The occurence of ferroelectric phases as well as properties of cholesteric and blue phases alternate with the number of linking atomes between steroid and atomatic system
On the Problem of Bromide Control in a TI3+ -perturbed Belousov-Zhabotinsky Oscillator
Authors: Murányi Szilvia , Noszticzius Zoltán
Published: February 2015

It is shown that TI3+ as a bromide removing perturbant of the BZ oscillators is superior to Ag+ in several aspects. A most important advantage is that the upper limit of the actual Br- concentration can be calculated from the potential of a bromide selective electrode in the presence of the corrosive TI3+ ions. Experimental Potentiometrie traces of a bromide selective electrode in a TI3+ perturbed BZ system show that the Br- concentration stays much below its critical concentration during the oscillations. These observations suggest that free Br- is not the critical intermediate formed during reduction of Ce4+ and responsible for the negative feedback associated with the oscillations.
79Br Nuclear Quadrupole Relaxation in the High Temperature Modification of Niobium Pentabromide
Authors: Okubo Noriaki , Sekiya Harutaka , Ishikawa Chiaki , Abe Yoshihito
Published: February 2015

The spin-lattice relaxation time of 79Br NQR has been measured between 4.2 K and room temperature. The result is compared with that of 35Cl NQR in NbCl5. The origin of the relaxation is attributed to the quadrupolar interaction and the temperature dependence is explained by the Raman process. The Debye temperature is determined to be 94 K and the relaxation time is related with the NQR frequency through the covalency.
Molecular Motion in Solid Tetramethylammonium Tetrafluoroborate
Authors: Torre S. , Ferloni P.
Published: February 2015

Measurements of 11B and 1H NMR relaxation times, differential scanning calorimetry and thermomechanical analysis, carried out on polycrystalline (CH3)4 NBF4 from room temperature to about 100 K, have permitted to discuss the crystal dynamics of this salt and to analyze the nature of the phase transition occurring at ≈ 150 K. Moreover, by means of an evaluation of the 11B quadrupole coupling constant, information about the position of the F atoms has been obtained. An explanation of the NMR data in terms of an order-disorder phase transition involving the F- ions is given.
A Microscopic Theory of a Single Hydrogen Centre in a Magnesium Crystal
Authors: Gnirßt M. , Wahl F.
Published: February 2015

A microscopic theory of a single hydrogen center embedded in a magnesium crystal is presented. Starting with a many-particle Schrödinger equation, an adiabatic decoupling yields in an electronic system a protonic system and a host lattice system. The storage energy is defined to consist of an electronic part and lattice contributions. The electronic problem is treated with the help of a special energy difference procedure developed by Wahl et al. This procedure is applied in a higher approximation to calculate the electronic energy difference eigenvalue between a metal crystal with and without a hydrogen impurity. The lattice problem is treated in the classical harmonic approximation.
Peripheral Stochasticity in Tokamaks.The Martin-Taylor Revisited
Authors: Viana R. L. , Caldas I. L.
Published: February 2015

We analyse the effect of an Ergodic Magnetic Limiter on the magnetic field line dynamics in the edge of a large aspect-ratio Tokamak. We model the limiter action as an impulsive perturbation and use a peaked-current model for the Tokamak equilibrium field. The theoretical analysis is made through the use of invariant flux functions describing magnetic surfaces. Results are compared with a numerical mapping of the field lines
Polarisation in the Temperature Equilibration of Anisotropic Plasmas
Authors: Wolf U. , Schamel H.
Published: February 2015

The polarisation effect on the isotropisation of a magnetized bi-Maxwellian plasma is investigated in the weak coupling approximation. Based on the Rostoker collision operator, which reduces in the magnetic field free limit to the Balescu-Lenard operator, the equipartition frequency v is evaluated numerically for B→0 and analytically for B→∞, respectively. This frequency, depending nonlinearly on ε and B, describes the approach to thermodynamic equilibrium of the anisotropy parameter ε = T⊥/T‖ via dε/dt - (1 - ε) ν(ε, B). It is found that in both limits dynamical screening makes a negligible contribution to the relaxation process. For finite B a simplified, yet unexploited expression for ν(ε, B) is presented, which invokes three new functions
Comparison of Different Methods of Abel Inversion Using Computer Simulated and Experimental Side-On Data
Authors: Pretzier G. , Jäger H. , Neger T. , Philipp H. , Woisetschläger J.
Published: February 2015

A recently devised new method for numerical Abel inversion is compared with four other commonly used methods. One of them, the convolution method, is employed in computer tomography for reconstructing asymmetrical objects. It is investigated whether this method can be adapted for the case of radial symmetry. As a first approach the comparison is performed by computer simulation. Special attention is given to the propagation of errors according to their origin. The result is a recipe for minimizing errors and for choosing the optimal method for reconstruction. The second step is a comparison of experimentally obtained radial profiles with functions resulting from Abel inversion of measured side-on data. Thus it is shown that the concept developed by computer simulation can be applied in practice
Monte Carlo Simulations of Water under Supercritical Conditions. II. Convergence Characteristics and the System Size Effects
Authors: Kalinichev A. G.
Published: February 2015

The size dependence and convergence rates of thermodynamic averages during Monte Carlo simulations of supercritical water in a wide range of densities have been analysed and compared with simulations under normal conditions. It is shown that the fluctuations of internal energy (enthalpy) in NPT-ensemble Monte Carlo simulations of high-temperature water are strongly correlated with fluctuations of volume and the convergence of the thermodynamic averaging under such conditions depends on the frequency of volume-changing moves and may be considerably improved by increasing this frequency by a factor of 3 - 10 relative to generally accepted values
Probing the Electronic Structure of Y-Ba-Cu-O Superconductors by Copper NQR/NMR
Authors: Brinkmann D.
Published: February 2015

abstract

The paper discusses some NQR/NMR studies performed on Y-Ba-Cu-O superconductors at the University of Zürich. It is shown how the resonance methods can yield information on electronic properties of quite different character. The review deals with: (1) the temperature and pressure dependence of Cu NQR frequencies in YBa2Cu4O8(1-2-4); (2) an NQR study of the properties of Ca substituted 1-2-4; (3) the temperature dependence of the Cu Knight shifts in 1-2-4; (4) the NMR of plane Cu2 in the paramagnetic state of YBa2Cu3O6 ; (5) the dependence on temperature, pressure and orientation of the Cu spin-lattice relaxation in 1-2-4.
Cesium Iodometallates(III), Cs3M2I9, with M = Rare Earth. A Structural Investigation by 127I NQR
Authors: Lenck Marco , Weiss Alarich
Published: February 2015

The 127NQR spectra of cesium enneaiododimetallates Cs3M2I9, M = Dy, Ho, Er, Yb, Y and Tb, Sm, Nd, Pr have been studied as a function of temperature. The compounds are characterized by X-ray powder diffraction, too. The first group of compounds, M = Dy • • • Y, belongs to the family of Cs3Cr2Cl9-type enneahalogenodimetallates (III). The crystal structure of the second group, M = Tb ...Pr , is less symmetric, as in the 127I NQR the presence of two crystallographically independent iodines shows up. Nuclear quadrupole coupling constants for the terminal and bridging halogens have been calculated from the NQR frequencies. The dependence of the NQR frequencies and of the crystal structure from the radius of the RE3⊕ -ion is discussed. The NQR spectra reveal phase transitions of the investigated enneaiododimetallates (III), for which Tlr also depends on r(RE3⊕). Positive temperature coefficients of the 127I have been found and the influence of π-bond character is considered.
NQR and X-ray Studies of [N(CH3)4]3M2X9 and (CH3NH3)3M2X9 (M = Sb,Bi; X = Cl,Br)
Authors: Ishihara Hideta , Watanabe Koichi , Iwata Ayako , Yamada Koji , Kinoshita Yoshihiro , Okuda Tsutomu , Krishnan V. G. , Dou Shi-qi , Weiss Alarich
Published: February 2015

35Cl, 81Br, 121Sb, and 209Bi NQR of the title compounds was observed. According to the results of the temperature dependences of NQR frequencies and the DTA measurements, phase transitions take place in [N(CH3)4]3Bi2Br9 (Ttr=183K), [N(CH3)4]3Bi2Cl9 (Ttr = 155K), and (CH3NH3)3Bi2Cl3 (Ttr = 200 and 249 K). 2D NMR spectra for partially deuterated (CH3ND3)3Bi,Br9 showed that the phase transitions in this compound are related to the motion of the methylammonium cations. Single-crystal X-ray work at room temperature shows that the space group for [N(CH3)4]3Sb2Cl9 is P63/mmc with a = 925.1 pm, c = 2173.4 pm, Z = 2. For (CH3NH3 ) 3Sb2Br9 the space group is P3ml with a = 818.8 pm, c = 992.7 pm, Z = 1; in both cases the cations show dynamical disorder. The Rietveld analysis of the powder X-ray diffraction for (CH3NH3)3Bi2Br9 reveals the space group P3ml with a = 821.0, c - 1000.4 pm, Z = 1 at room temperature; the compound is isomorphous with (CH3NH3 )3Sb2Br9 . The crystal symmetries of the low-temperature phases of (CH3NH3)3Bi2Br9 and [N(CH3)4]3Bi2Br9 were deduced from the results of the NQR spectroscopy
Coordination of Ortho-Chlorines in Copper (I) and Silver (I) 2,6-Di- and 2,4,6-Trichlorophenolates
Authors: Wulfsberg Gary , Jackson Debra , Ilsley William , Dou Shi-qi , Weiss Alarich , Gagliardi John
Published: February 2015

The crystal structure of (Ph3P)2AgOC6H2Cl3 (I) is reported along with the syntheses and 35Cl and 63Cu NQR spectra of I and several related silver (I) and copper (I) 2,6-di- and 2,4,6-trichlorophenolates containing phosphines, phosphites, and pyridine as co-ligands. I crystallizes in space group P21/cc with a= 16.692(4) Å, b= 17.942 (4) A, c = 12.857 (3) Å, β = 97.60 (1)°, F = 3816.68 Å3, and Z = 4. The final R (F) = 0.0475 and R (W) = 0.0396. Ag is coordinated in a trigonal planar geometry by the P atoms of the two triphenylphosphine ligands and the O atom of the chlorophenolate; Ag is then capped by one ortho-chlorine of the trichlorophenolate ligand at a distance of 3.160 (2) Å. In the 35Cl NQR spectrum of this compound the two ortho-chlorines of the trichlorophenolate ligand have a large frequency difference of 1.500 MHz, indicating that one ortho-chlorine is coordinated to the silver; 35Cl NQR spectra of related complexes are also presented and discussed. The 35Cl NQR frequency differences of coordinated and non-coordinated ortho-chlorines in metal chlorophenolates correlate well with the metal-chlorine distances but not with the metal-chlorine-carbon bond angles. A different correlation is found for the silver complexes of dichloroalkanes; possible reasons for this are discussed.
35Cl NQR Spectra of Organyl(chloroalkyl) Sulfides
Authors: Voronkov Mikhail G. , Dolgushin Gennadii V. , Feshin Valentin P. , Turchaninova Lyudmila P. , Korchevin Nikolai A. , Deryaghina Eleonora N.
Published: February 2015

The 35Cl NQR spectra of organyl(chloroalkyl) sulfides ClCH2S(CH2)nCH3, n = 0-11, Cl(CH2)mSR, m = 1 - 3 and alkyl(chloromethyl selenides ClCH2SeR (R = C2H5 , C3H7 ) have been obtained. In going from m = 1 to m = 2, the electron density on the CI atom in the series Cl(CH2)mYR increases when Y = S and decreases when Y = O.
Spatial Electron Density Distribution of Chlorine Atoms in Molecules of the Series Cl2C = CXX'
Authors: Feshin Valentin P. , Polygalova Gelena A. , Shchepin Vasilii V. , Sapozhnikov Yurii E.
Published: February 2015

The EFG asymmetry parameters at 35Cl nuclei have been measured for polycrystalline compounds of series Cl2C = CHX (X = OR, OCOR) and Cl2C = C(Cl)OCOR at 77 K. For the Cl trans-atoms in molecules Cl2C = CHX, the q values are equal or close to zero. For the Cl cis-atom of these compounds and for all Cl atoms of compounds Cl2C = C(Cl)OCOR, η ~ 6 - 9%. It was shown that the deviation from the axial symmetry of electron distribution of Cl atoms in these compounds is due to the influence not of the geminal, but of a vicinal atom or group directly through the field. The expected p, π -conjugation between the unshared electron pair of halogen and the Ti-electron system of double bond is absent in the molecules studied.
NQR and Crystal Structure of 4,5-Dichloroimidazole, C3H2N2Cl2
Authors: Dou Shi-Qi , Weiss Alarich
Published: February 2015

The two line 35Cl NQR spectrum of 4,5-dichloroimidazole was measured in the temperature range 77≦ T/K ≦ 389. The temperature dependence of the NQR frequencies conforms with the Bayer model and no phase transition is indicated in the curves v ( 35Cl)= f(T). Also the temperature coefficients of the 35Cl NQR frequencies are "normal". At 77 K the 35Cl NQR frequencies are 37.409 MHz and 36.172 MHz and at 389 K 35.758 MHz and 34.565 MHz.

The compound crystallizes at room temperature with the tetragonal space group D4
4-P41212, Z = 8 molecules per unit cell; at 295 K : a = 684.2(5) pm, c = 2414.0(20) pm. The relations between the crystal structure and the NQR spectrum are discussed.
The ab initio Calculation of Nuclear Quadrupole Coupling Constants with Special Reference to 33S
Authors: Palmer Michael H.
Published: February 2015

The ab initio calculation of 33S nuclear quadrupole coupling constants (NQCC) for a range of S-containing compounds with S2, S4 and S6 bonding types is described. All of the calculations used a triple zeta valence + polarisation basis set (TZVP) of gaussian type orbitals; all of the molecules were studied at the TZVP equilibrium geometry. The electric field gradients (EFG) calculated were correlated with the experimental NQCC obtained by either microwave spectroscopy (MW), nuclear quadrupole resonance (NQR) or NMR relaxation methods; although the experimental data cover a wide diversity of chemical types over a long period of time, the slope of the relationship between the EFG (qii) and the NQCC (χii) yields a value for the 33S atomic quadrupole moment of - 0.064 barn, very close to recent calculations with a large atomic basis set, and to experimental data. The relationship between the EFG tensor components and the internal molecular structure features is discussed for a diverse series of molecules.
Phase Transitions in Bis(4-chlorophenyl)sulfone as Studied by 35Cl FT-NQR
Authors: Nakayama Hirokazu , Eguchi Taro , Kishita Michihiko
Published: February 2015

The temperature dependence of 35Cl NQR frequencies in bis(4-chlorophenyl)sulfone was measured in the temperature range of 4.2-297 K. Below 115 K four NQR lines due to four inequivalent chlorines exist in the commensurate phase, contrary to the single NQR line reported by Corbero et al. It follows that the commensurate-incommensurate transition is of the first-order, and the incommensurate-normal transition at 150 K is quasi-continuous. It is also suggested that the successive phase transitions are triggered by the small angle rotation of the molecules about their C2-axes.
Reorientational Motion of Hydrogen Bonded Octahedral Complex Anions in Hydrazinium Hexachlorostannate(IV), (N2H5)2SnCl6, as Studied by 35Cl NQR Spin-Lattice Relaxation Measurements
Authors: Kume Yoshio , Tokoro Maki , Asaji Tetsuo , Ikeda Ryuichi , Nakamura Daiyu
Published: February 2015

The temperature dependences of NQR frequencies and spin-lattice relaxation times, T1Q, of 35Cl in (N2H5 ) 2SnCl6 were measured. Four NQR signals distributed in a fairly wide frequency range were observed, the lowest-frequency line exhibiting an anomalous positive temperature coefficient. The highest-frequency line showed a steep temperature dependence. These results could be interpreted by considering the intermolecular interaction between CI and - NH2 in N2H5
+ . Below ca. 250 K, T1Q of the upper three signals exhibited a gradual decrease upon heating, explainable by lattice vibrations, while a shallow T1Q minimum, ascribable to the modulation of electric quadrupole interaction, was observed at ca. 110K for the lowest-frequency signal. The reorientation of [SnCl6]2- was elucidated to be highly anisotropic, in that it reorients about one of the CI-Sn-Cl axes much more frequently than about the other two axes. The activation energies were determined to be 62 and 94 kj mol -1 for the respective reorientations.
The 35Cl NQR Temperature Dependence of Hexa- and Octachlorocyclophosphazene
Authors: Koukoulas Alexander A , Whitehead M. A.
Published: February 2015

The 35Cl NQR temperature dependence in (PNCl2)3 and (PNCl2)4 was measured between 77 K and 293 K. The dependence in both compounds was smoothly varying. A sudden decrease in T2* near 112 K indicated the presence of a strong broadening mechanism in (PNCl2)3. The nature of this mechanism is interpreted in terms of the Cl spin-lattice relaxation
Weak Complexes of Dinitrogen: An Approach to the 14N-Nuclear Quadrupole Coupling Constant of Free N2
Authors: Legon A. C. , Fowler P. W.
Published: February 2015

The 14N-nuclear quadrupole coupling constants χaa(14N<2>) and χaa(14N(1)) for the ground-states of the dimers 14N(2)
14N(1) • • • HCCH and 14N(2)
14N(1) • • • HC15N have been corrected for zero-point effects and for the electrical effects of the subunit HX to give two estimatesχ(14N) = -5.01 (13) and - 5.07 (8) MHz, respectively, for the coupling constant of the isolated 14N2 molecule
A Computer-controlled, Fully Automatic NMR/NQR Double Resonance Spectrometer
Authors: Zhenye Feng , Lücken Edwin A. C , Diolot Jacques
Published: February 2015

A completely automatic computer-controlled NMR/NQR double resonance spectrometer is described. It features automatic tuning of the low, variable frequency power amplifier, thus permitting untended use over long periods, with high sensitivity and signal reproducibility. The sample is transferred between the low-frequency, zero-field region and the high-field region using compressed air and the possibility of switching on a field of several tens of gauss during the transfer of the sample is also included
NQR Spin Echo in the Effective Fields of Multiple-Pulse Sequences
Authors: Furman G. B. , Kadzhaya I. M. , Kibrik G. E. , Poljakov A. Yu. , Shaposhnikov I. G.
Published: February 2015

Results of a study, both theoretical and experimental, of a new kind of NQR spin echo technique are reported and discussed
A Contribution to the Microwave Spectra of eis- and trans-2,3-Dimethyloxirane by Fourier Transform Spectroscopy
Authors: Hartwig Holger , Dreizler Helmut
Published: February 2015

Microwave Fourier transform spectroscopy was used to reinvestigate the rotational spectra of cisand trans-2,3-dimethyloxirane. The potential barriers hindering the internal rotation, internal rotation parameters, and partial rs-structures were determined.
The Rotational Spectrum of 2,2-Dimethyloxirane
Authors: Hartwig Holger , Dreizler Helmut
Published: February 2015

The microwave spectrum of 2,2-dimethyloxirane (isobutylene oxide) in the ground and torsionally excited states was assigned and analyzed. The potential barriers hindering the internal rotation described by V3 = 11.312(9) kJ/mol and V’1 2 = 1.059(32) kJ/mol and the angles between the axes of inertia and the internal rotation axes were determined.
Experimental Realization of Stokes Modes of the Pipe by Lorentz Excitation
Authors: Pysik A. , Heber J.
Published: February 2015

The complete set of the Stokes modes of the pipe was first given by Brösa and Böberg. Two of these modes for an incompressible fluid were now realized in a transparent tube and detected by a laser light cut. Their velocity fields and lifetimes were compared with the theoretical predictions, and good agreement was found. The modes were generated by Lorentz force fields of appropriate symmetry induced by an electrical current through the fluid and external magnetic fields. For higher excitation intensities effects of mode coupling could be observed
Nitrogen Nuclear Quadrupole Resonance Dips in the Proton Spin Relaxation Dispersion of Nematic and Smectic Thermotropic Liquid Crystals
Authors: Pusiol D. J. , Humpfer R. , Noack F.
Published: February 2015

The Larmor frequency dependence of the proton spin relaxation time, obtained by means of the fast field-cycling NMR technique, has been used to study the 14N quadrupole coupling constant K and its asymmetry parameter η in the nematic and smectic phases of some liquid crystalline azoxybenzenes (PAA, BAB, HAB, HpAB), cyanobiphenyls (8CB, 9CB, 11CB) and oxycyanobiphenyls (9 OCB). Due to fast molecular reorientations, the effective quadrupole coupling constants are relatively small, whereas surprisingly the asymmetry parameters are rather large. The temperature dependence of both K and η within the mesophases, as well as their discontinuities at the different mesophase transitions, can be interpreted by the anisotropy of molecular rotations. It is found that temperature effects are significantly more pronounced for the (biaxial) smectic-C phase of the heptyloxyazoxybenzene (HpAB) than for the (uniaxial) smectic-A phase of the various investigated cyano- and oxycyanobiphenyls. As a rule, η turned out smaller in the smectic than in the nematic state, whereas K has similar values in both phases
About the Radical Formation in the Pyrolysis of Formic Acid at High Temperatures
Authors: Klatt M. , Röhrig M. , Wagner H. Gg.
Published: February 2015

The formation of radicals in the HCOOH pyrolysis was investigated in the temperature and density range between 1450 and 2450 K and 2 • 10-6 and 1.2 • 10-5 mol /cm3, respectively. The small amount of radicals found indicates that a radical forming reaction path in the formic acid pyrolysis is smaller than 0.2% of the total decomposition rate
Quadrupole Hyperfine Structure in the Rotational Spectra of Sulfuryl Chloride
Authors: Merke Ilona , Dreizler Helmut
Published: February 2015

The nuclear quadrupole coupling of [35Cl,35Cl]- and [35Cl,37Cl]-sulfuryl chloride, SO2Cl2 was investigated using waveguide microwave Fourier transform (MWFT) spectroscopy. The analysis was performed with direct diagonalization of the Hamiltonian matrix. It was possible to determine the complete coupling tensor with high accuracy. SO2
35Cl2 : χaa ( 35Cl1) = χaa(35Cl2) = -33.049(6) MHz, χcc (35Cl1) = χcc (35Cl2) = 40.356 (9) MHz, χab (35Cl1) = - χab(35Cl2) = + 52.67 (63) MHz. SO2
35C137C1: xaa ( 35Cl)= -29.582(17) MHz, χcc(35Cl) = 40.340(25) MHz, χab(35Cl)= +52.3(14) MHz, χaa(37Cl)= -28.723(18) MHz, χcc(37Cl) = 31.822(28) MHz, χab,(37Cl) = + 37.3(19) MHz. We also determined the quadrupole coupling constants in their principal axes system. In comparison with the structure, the z-axis of the coupling tensor was found to be tilted 2.0° out off the S-Cl bond axis
Combination of EXAFS and Differential Anomalous X-ray Scattering for Studying Ni 2 Zr Amorphous Alloy
Authors: Babanov Yu. A. , Sidorenko A. F. , Shvetsov V. R. , Bionducci M. , Licheri G. , Navarra G. , Ageev A. L. , Vasin V. V.
Published: February 2015

In this paper we report a first application of the new idea of combining EXAFS and differential anomalous scattering techniques to obtain partial distribution functions for a binary amorphous sample. This method has been successfully employed in extracting Ni-Ni and Ni-Zr pair distribution functions for Ni2Zr prepared by mechanical alloying. A comparison with results from previous studies is also reported.
Hydrogen in Electrodynamics. IX. The Equations of Second Order
Authors: Sallhofer Hans
Published: February 2015

The equation of second order of electrodynamic hydrogen are derived.
Determination of some Dye Parameters by Polarized Fluorescence Spectroscopy
Authors: Wolarz Eryk
Published: February 2015

A method of determining the angles between the emission and absorption dipole moments and the molecular symmetry axis is described. The order parameters  and  of nematic-dye mixtures are also calculated. The method is applied in investigations of tricarboxylic acid derivatives dissolved in the nematic mixture E 18 (Merck).
Short Range Structure of Amorphous Ni50Ta50-Alloys by Means of X-Ray- and Neutron-Diffraction
Authors: Uhlig H. , Rohr L. , Güntherodt H.-J. , Fischer P. , Lamparter P. , Steeb S.
Published: February 2015

Amorphous Ni50Ta50-samples with their high crystallization temperature of 985 K were investigated. To evaluate the three partial structure factors of amorphous Ni50Ta50 one X-ray diffraction experiment was performed with Ni50Ta50 and two neutron diffraction experiments with Co10Ni40Ta50 and with Ni50Ta50, respectively. The Bhatia-Thornton partial structure factor SCC(Q) indicates rather strong chemical short range order which also explains the premaximum observed in the Faber-Ziman partial SNiNi(Q)-function. The nearest neighbor distance is 2.82 Å for Ni-Ni, 2.91 Å for Ta-Ta, and is shortest for Ni-Ta, 2.44 Å. The coordination numbers are NNiNi = 4.9, NTaTa = 8.2, and NNiTa = 6.0. We report on the chemical short range order and the possible binding behavior in a-Ni50Ta50 and compare the present results with those reported in the literature on a-Ni40Ti60 as well as on a-Ni55Ta45
Molecular Reorientation of Methanol in Mixtures with Carbon Tetrachloride
Authors: Zeidler M. D. , Gill D. S. , Zeidler M. D.
Published: February 2015

Proton and oxygen-17 nmr relaxation rates of CD3
17OH as well as deuteron nmr relaxation rates of CH3OD were measured in mixtures with carbon tetrachloride at different compositions and temperatures. By varying the 170-content different contributions to the proton relaxation rate could be separated and from the 17O-H dipolar interaction contribution the correlation time τ2
OH of the OH bond was determined. Using these correlation times the composition dependence of the deuterium and oxygen-17 quadrupole coupling constants of methanol was derived. A strong variation of the coupling constants over the measured composition range is evident
Elastic Scattering of Electrons by Helium Atoms at Intermediate Energies
Authors: Chhaya V. M. , Tarwadi J. J. , Chhag Smita
Published: February 2015

The unitarised Eikonal Born series (UEBS) method has been used successfully by Byron et al. for elastic scattering of electrons and positrons by hydrogen atoms. Here an attempt is made to apply the UEBS method in the case of elastic scattering of electrons by helium atoms. The total and differential cross sections are calculated for the energy range 100-700 eV. The results are compared with experimental and other theoretical results. It is found that the results obtained with the UEBS method agree best with the experimental results.
Structural Phase Transitions in (n-C3H7NH3)2SbBr5
Authors: Jakubas R. , Bator G. , Foulon M. , Lefebvre J. , Matuszewski J.
Published: February 2015

Dielectric, DSC, thermal expansion and preliminary X-ray diffraction studies on (n-C3H7NH3)- SbBr5 are reported. It was found that this crystal undergoes a complex sequence of phase transitions. On cooling: phase I → phase II at 188.7 K (continuous), II → III at 165 K (1st order, ΔS = 26.8 J/mol K), III → IV at 137 K (1st order, 1.6 J/mol K). On heating: IV → III at 154 K, III → II’ at 168 K, II’ → II at 177 K (1st order, 2.8 J/mol K), II → I at 189 K. All 1st order phase transitions are likely due to the motion of the n-C3H7NH3
+cations. The dielectric dispersion studies between 100 Hz-1 MHz within the phases I and II indicate a fast reorientational motion of dipoles with τ < 10−7
S.
Superposition and Polarization Effects on the Electron Density of Lone Pairs
Authors: Olovsson Ivar , Ptasiewicz-Bak Halina , Mclntyre Garry J.
Published: February 2015

There appears to be conflicting experimental evidence on the redistribution of the electron density in the lone-pair and other regions of a molecule due to the interaction with its nearest neighbours. In some experimental as well as theoretical deformation density maps a decrease in the lone-pair density has been reported, whereas in other cases an increase has been found. It appears that two major, counteracting factors are responsible for these differences (apart from experimental errors in the diffraction studies and limited accuracy in the theoretical calculations): an increase in the lone-pair density is expected due to the polarizing influence of the neighbours, whereas simple superposition of the isolated monomer deformation densities will lead to an apparent decrease due to the overlap with the negative contours of the neighbouring atom. Depending on which of these factors is the dominant one, an increase or decrease may thus be observed.

These points are illustrated by recent results on nickel sulfate hexahydrate and some other hydrogen-bonded compounds. The electron density based on the fitted deformation functions of all atoms in the structure is compared with the individual densities calculated from deformation functions of the separate monomers. In this way the effects of simple superposition of the individual densities have been studied, and a partitioning of the electrostatic and polarization contributions to the hydrogen bonds and other relatively weak bonds to the oxygen lone-pairs attempted.
The Identification of Phonon-Phonon Interactions in Anharmonic Crystals by X-Ray Diffraction Data
Authors: Tsarkov A. G. , Tsirelson V. G.
Published: February 2015

The effect of anharmonic atomic vibrations on the elastic scattering of X-rays by a crystal is treated by time-independent perturbation theory. The complete expression for the anharmonic temperature factor (TF) in the high-temperature limit is presented for atoms in general positions. The phonon-phonon interactions in an anharmonic crystal may be identified with X-ray diffraction data by using various temperature and scattering vector q dependencies of different anharmonic contri-butions to the TF. The expression for the intensity of elastic scattering by an anharmonic crystal contains an additional factor -the anharmonic cross-term. This term has to be taken into account for obtaining the unbiased thermal parameters of fourth order in | q | from X-ray diffraction data.