bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic Structure of the C60 Fragment in Alkali- and Alkaline-earth-doped Fullerides
Authors: Böhm Michael C. , Schedel-Niedrig Thomas , Werner Hartmut , Schlögl Robert , Schulte Joachim , Schütt Johannes
Published: February 2015

The electronic structure of the C50 fragment in alkali-and alkaline-earth-doped fullerides is studied theoretically. With increasing metal-to-C 60 charge transfer (CT) the n electronic properties of the soccerball are changed. In the undoped solid and for not too high a concentration of doping atoms the hexagon-hexagon (6-6) bonds show sizeable double bond character while the hexagon-pentagon (6-5) bonds are essentially of single bond type. In systems with a high concentration of doping atoms this relative ordering is changed. Now the 6-5 bonds have partial double bond character and the 6-6 bonds are essentially single bonds. The high ability of the C 60 unit to accomodate excess electrons prevents any sizeable weakening of the overall n bonding in systems with up to 12 excess electrons on the soccerball. A crystal orbital (CO) formalism on the basis of an INDO (intermediate neglect of differential overlap) Hamiltonian has been employed to derive solid state results for potassium-and barium-doped C 60 fullerides. For both types of doping atoms an incomplete metal-to-C 60 CT is predicted. In the potassium-doped fullerides the magnitude of the CT depends on the interstitial site of the dopant. The solid state data have been supplemented by INDO and ab initio calculations on molecular C 60 , and C^, 2 , -. The calculated bondlength alternation in the neutral molecule is changed in C 6 ö~ where the length of the 6-6 bonds exceeds the length of the 6-5 bonds. The geometries of the three molecular species have been optimized with a 3-21 G* basis. The theoretically derived modification of the C 60 (7r) electronic structure as a function of the electron count is explained microscopically in the framework of two quantum statistics accessible for n electronic ensembles. In the 7r ensemble of the C W) fragment so-called hard core bosonic properties are maximized where the Pauli antisymmetry principle has the character of a hidden variable only. Here the electronic degrees of freedom are attenuated only by the Pauli exclusion principle. This behaviour leads to the changes in the ir electronic structure mentioned above.
Dielectric Studies of trans,trans-4'-n-Pentyl-bicyclohexyl-4- carbonitrile (5CCH) under High Pressure
Authors: Brückert T. , Würflinger A.
Published: February 2015

Dielectric studies on the static and complex permittivity have been performed on trans,trans-4'-n-pentyl-bicyclohexyl-4-carbonitrile (5 CCH) in the pressure range 0.1-200 MPa, the frequency range 1 kHz-13MHz and the temperature range 300-390 K. Phase transitions between the isotropic, nematic, smectic B (metastable), and crystalline state have been recorded as steps in the static permittivity. Thus the phase diagram of 5 CCH was established. In particular the slow relaxation process in the nematic and smectic phase has been investigated. The dielectric relaxation time τ|| increases by a constant factor of 210 on passing the nematic-smectic B phase transition. From the pressure and temperature dependences of τ we have calculated the activation volumes (Δ≠ V/cm3 mol-1 = 88-65 (nematic), = 70-45 (smectic) and ≈ 32 for the isotropic phase) and activation enthalpies (Δ≠H/kJ mol-1 = 76-60 (nematic), ≈ 60 (smectic) and ≈ 37 for the isotropic phase), respectively, which are compared with previous results on similar homologous series. The activation parameters increase significantly, when the rigid phenyl ring is replaced by the more flexible cyclohexyl ring.
The Influence Of Matter And Black-Body Radiation Photons On The Dipole Polarizabilities A And γ Of Atoms
Authors: Hohm Uwe
Published: February 2015

The influence of the surroundings on the linear dipole polarizability α and second hyperpo-larizability γ is discussed in terms of the density ϱM of isotropically distributed matter as well as the density ϱp of thermal black-body radiation photons, α and γ of the rare gas atoms are studied as examples. At standard conditions, both effects are of comparable size for the rare gases. Possible consequences for ion-molecule reaction rate constants in astronomical environments are suggested.
Laser Ionisation Spectroscopy Of Formyl Fluoride
Authors: Schmid Reiner P. , Jones Harold
Published: February 2015

A vibronic band of formyl fluoride near 39,511 cm-1 has been observed using multiphoton ionisation spectroscopy. From the analysis of the partially resolved rotational structure, the rotational parameters of the (0, 2, 0, 0, 0, 0) vibrational level of an electronic state near 39,000 cm ~1 have been determined: A = 92.50(1.46) GHz and (B + C)/2 = 11.23(30) GHz. The term value was determined to be 39,510.93(30) cm-1 .
Solid State Reaction Study Of The System Co-Li2CO3
Authors: Marini A. , Berbenni V. , Massarotti V. , Capsoni D. , Bruni G.
Published: February 2015

A detailed analysis of the reactive processes taking place in Co-Li2CO3 was performed by use of thermogravimetry and X-ray diffraction. A reaction model is proposed which accounts for the nature, stoichiometry, and amount of the phases present, at room temperature, in samples subjected to different thermal treatments. In particular it is shown that the thermal treatment influences substantially the final lithium content and the relative amount of the Li-containing phases. The results obtained for powdered samples are compared with those obtained in a previous work for plaques.
Effect of Rotation on Thermal Instability in Rivlin-Ericksen Elastico-Viscous Fluid
Authors: Sharma R. C. , Kumar P.
Published: February 2015

The thermal instability of a layer of Rivlin-Ericksen elastico-viscous fluid acted on by a uniform rotation is considered. For stationary convection, a Rivlin-Ericksen elastico-viscous fluid behaves like a Newtonian fluid. It is found that rotation has a stabilizing effect and introduces oscillatory modes in the system. The visco-elasticity also introduces oscillatory modes in the system. A suffi-cient condition for the non-existence of overstability is also obtained.
A Theoretical Modeling of the Static and Dynamic Polarizability of O2- in Large and Complex Oxides
Authors: Ray D. , Anton H. , Schmidt P. C. , Weiss Al.
Published: February 2015

A time-dependent approach is employed in conjunction with a crystal potential model to study the environment-specific optical linear response of the O2- ions in a number of cubic oxides with varying number of constituents, unit-cell dimension and degree of complexity. It is shown that the static polarizability of the anion may vary significantly depending on the position of the anion within the unit-cell. Due to neglect of overlap compression, our method has limited success in predicting the refractive indices of large crystals of complex structures. For small binary oxides the frequency-dependent polarizability of the O2- ion is found to exhibit the first poles close to the ultraviolet absorption edges ascribed to the lowest excitonic transitions in these crystals.
Perylene-like Dyes in Liquid Crystalline Media
Authors: Mykowska Ewa , Bauman Danuta
Published: February 2015

The spectral and electrooptical properties of some dichroic fluorescent dyes (derivatives of 3.4,9,10-perylenetetracorboxylic acid and of 3,4,9-perylenetricarboxylic acid) in isotropic solvents and nematic liquid crystals have been studied. The order parameter of the dyes in the anisotropic matrices has been determined by means of optical spectroscopy methods. Moreover, the influence of the dye addition on the nematic-isotropic phase transition temperature of the pure host has been investigated. It was found that some of the dyes studied can be utilized in guest-host liquid crystal display devices.
Investigation of the Structure of Liquid Pyridine: a Molecular Dynamics Simulation, an RISM, and an X-ray Diffraction Study
Authors: Bakó Imre , Radnai Tamás , Pálinkás Gábor
Published: February 2015

The structure of liquid pyridine is investigated by molecular dynamics simulation and the RISM integral equation methods. The calculated total radial distribution functions (RDF) are compared with the experimental RDF’s, obtained by X-ray diffraction measurement. It is shown that the local structure of liquid pyridine is mainly determined by the dipole-dipole interaction between the molecules. The local order is characterized by the pair distribution functions, angular correlation functions and orientational distributions. Dynamical properties (self-diffusion coefficients, rotational correlation times and reorientational correlation times) calculated on the basis of MD results are in good agreement with experimental data.
Liquid Crystals and Glasses in Binary Systems from Sodium and Alkali-Earth Metal Butyrates
Authors: Mirnaya T. A. , Bereznitski Y. V. , Volkov S. V.
Published: February 2015

The temperature and composition ranges of liquid crystal and glass formation have been established for the binary mixtures of mesogenic sodium butyrate with non-mesogenic magnesium, calcium and strontium butyrates by means of differential thermal analysis and hot stage polarization microscopy. The formation of a vitreous optically anisotropic mesophase has been found for binaries of sodium butyrate with calcium and strontium butyrates.
EPR Studies of Tb 4+ in Single Crystals of Zircon and Scheelite Structure Silicates and Germanates
Authors: Hansen S. , Mosel B. D. , Müller-Warmuth W. , Fielding P. E.
Published: February 2015

Electron paramagnetic resonance spectra of tetravalent terbium ions have been observed in host crystals of ZrSiO4 , HfSiO4 , ThSiO4 , ThGeO4 (zircon structure) and ZrGeO4 , HfGeO4 (scheelite structure) at X band and Q band and various temperatures. The spin Hamiltonian parameters have been determined from the rotational diagrams; the zero field splittings turned out to be extremely large, so that complex spectra far from the strong magnetic field limit had to be analyzed. In all the compounds Tb4+ substitutes for the tetragonal metal lattice sites. The incorporation of terbium, the origin of the large second-order parameters and comparisons with the spectra of trivalent gadolinium in similar systems are discussed.
ESR of Gamma Irradiation Damage Centers in Single Crystals of Some Glutamic Acid Derivatives
Authors: Zengin D. Mehmet , Birey Mehmet , Aktas Huseyin , Hancer Ahmet , Murathan Atilla M.
Published: February 2015

We have observed four radicals in the ESR spectra of y-irradiated single crystals of some glutamic acid derivatives. These radicals, produced by gamma-irradiation, in single crystals of N-Acetyl-L-Glutamic acid, L-Glutamic acid and DL-Glutamic acid hydrochloride were identified as CH3CONH, -C3H5 , -CH, and -NH2 radicals respectively.
THz Rotational Spectra of HBr Isotopomers in their υ = 0,1 States
Authors: Saleck Axel H. , Klaus Thomas , Belov Sergei P. , Winnewisser Gisbert
Published: February 2015

We have observed the pure rotational spectra of HBr isotopomers in their υ = 0 and υ = 1 states between 0.97 and 1.02 THz. i. e. the HBr Ј = 2-1 and the DBr Ј =4 - 3 transitions, respectively. In the analysis, all presently available rotational transitions of all isotopomers have been fitted to a Dunham-type Hamiltonian to obtain the isotopically invariant parameters, including vibrational and rotational expansion coefficients for the hyperfine constants. In the analysis, the vibrational expansion coefficients of the nuclear quadrupole interaction are determined up to second order, and up to first order for the nuclear spin-rotation interaction.
Fluorescence Properties of p-Quaterphenyl and p-Quinquephenyl Derivatives in Liquid Solvents
Authors: Kawski A. , Piszczek G. , Kubicki A.
Published: February 2015

Absorption, fluorescence and emission anisotropy spectra, as well as quantum yields and fluores-cence decay times of p-quaterphenyl (PQP), 4,4"'-bis-(2-butyloctyloxy)-p-quaterphenyl (BBQ), 2,5,2"",5""-tetramethyl-p-quinquephenyl (TMI) and 3,5,3"",5""-tetra-f-butyl-p-quinquephenyl (QUI) were investigated in several nonpolar and polar solvents. It was found that high quantum yield is accompanied by a short (not exceeding 1 ns) lifetime and considerable emission anisotropy in low viscosity solvents. For TMI and QUI, which incorporate as many as 5 phenyl groups, the quantum yield in dioxane is 0.98 and 0.97, respectively. In the case of molecules with 4 phenyl groups, the quantum yield is slightly lower, amounting to 0.91. Rotational motions of terminal phenyl groups cause a lower deactivation of the excitation energy of the singlet state S p the longer the linear molecule.
13C CP/MAS NMR Study of the Layered Compounds [C6H5CH2CH2NH3]2[CH3NH3]n - 1Pbnl3n+1 (n = 1, 2)
Authors: Ueda T. , Shimizu K. , Ohki H. , Okuda T.
Published: February 2015

13C CP/MAS NMR spectra were measured on the layered compounds [C6H5CH2CH2NH3]2[CH3NH3]n - 1PbnI3n + 1 (w = 1, 2). The linewidth of the resonance peak corresponding to the phenyl carbons changed with temperature. The maximum broadening took place at 363 K for both com-pounds. The activation energy E a for the reorientation of the phenyl group was determined to be 25 kJ mol- 1 for n = 1 and 26 kJ mol- 1 for n = 2. The frequency factor τ 0 was evaluated from the linewidth at 363 K. The value of the second moment, estimated from the maximum linewidth, was interpreted by assuming a 180° flip of the phenyl group around its two-fold axis. The similarity of the activation energies for the reorientation of the phenyl group suggested that the local structure and the molecular motion of the organic cations is little affected by the difference in the sub-structure of the inorganic layer in those compounds.
Magnetic Solitons in the 1-D Antiferromagnetic Chains of Li2Mn0.98Fe0.02F5 and Na2Mn0.98Fe0.02F5
Authors: Frommen Ch. , Mangold M. , Pebler J.
Published: February 2015

Measurements of the 57Fe Mössbauer effect and magnetic susceptibility have been performed on 57Fe-doped quasi-1-d antiferromagnetic chains of Li2MnF5 and Na2MnF5 as a function of temperature. The Mössbauer spectra, fitted by the Blume-Tjon model, show definite relaxation effects near the Neel temperature, which are attributed to short-range order with temperature-dependent relax-ation times. The soliton model of non-linear excitations was applied. Experimental data confirm the predicted exponential temperature dependence of the thermal excitation of moving domain walls. From the activation energies E2
A/k2 as a function of 1-d exchange energies J/k the local anisotropy energy D/k of -3.7(2) K was derived on the basis of sine-Gordon theory. This result is in fair agreement with -3.5(1) K previously derived from magnetic susceptibility measurements. In the light of our results there is some evidence that at low bridging angle ß ≈ 102(5)° a phase-transition from antiferromagnetic to ferromagnetic ordering occurs.
Phase Diagrams of Binary Alkanoate Systems with Common Cation: Potassium Isobutyrate-Propionate, and Sodium Butyrate-Isobutyrate
Authors: Mirnaya T.A. , Yaremchuk G.G. , Volkov S.V.
Published: February 2015

The phase diagrams of the binary mixtures of mesogenic potassium isobutyrate with non-mesogenic potassium propionate and mesogenic sodium butyrate with non-mesogenic sodium isobutyrate have been investigated by differential thermal analysis and hot stage polarization microscopy. Both systems have one eutectic and one metatectic phase equilibriums. Pecularities of liquid crystal formation in binary alkanoate systems with common alkali metal cation are discussed and compared with those of systems with common anion.
Time Reversibility and the Logical Structure of the Universe
Authors: Diebner Hans H. , Kirner Thomas , Rössler Otto E.
Published: February 2015

Both Fredkin's findings on the reversibility of logical operations and the novel capability to integrate Newton's equation of motion in an exactly reversible manner enables one to perform a gedankenexperiment in the form of a molecular dynamics simulation of the universe. This leads to a new validation of the reversible structure of the universe. Alternatively, the role of information needs to be upgraded in accordance with a recent proposal by Stonier.
A Remark on the Two-State Model of Dielectric Relaxation
Authors: Köhne H.-G. , Stockhausen M.
Published: February 2015

The two state model with exchange between the tumbling modes of the relaxing molecules is treated by computer simulation. Some results are given in dependence on the reorientational angular steps characterizing the respective states, which compare well with recent literature results obtained analytically.
Structure of Metallic Glasses: Experiments and Models
Authors: Lamparter P. , Steeb S.
Published: February 2015

The topological and the chemical short range order in metallic glasses is discussed by means of representative examples from the systems Ni-P, Ni-B, Nb-Ni, and Dy-Ni. The characterization of the chemical short range order, e.g. in terms of a short range order parameter, depends on the definition of an appropriate hypothetic statistical reference system. The consideration of the size effect is essential. Some structural features of metallic glasses point to relationships with the related individual crystalline phases, whereas other features show that the different types of metallic glasses have certain construction principles in common. Small angle scattering with hydrogenated metallic glasses suggests the presence of extended two-dimensional structures. Reverse Monte Carlo models reveal rather broad distributions of the local structural properties and show that metallic glasses are not built as assemblies of defined structural units.
1H and 19 F NMR Study of Cation and Anion Motions in Guanidinium Hexafluorozirconate
Authors: Grottel M. , Kozak A. , Pająk Z.
Published: February 2015

Proton and fluorine NMR second moments and spin-lattice relaxation times of polycrystalline guanidinium hexafluorozirconate and its deuterated analogue were studied in laboratory (60 MHz) and rotating (H1 = 20 G) frames over a wide range of temperature. An analysis of the experimental results enabled us to reveal a dynamical inequivalence of two crystallographically independent cations and an unexpected high mobility of nonspherical anion dimers. A comparison of the ions dynamics in 2:1 complex studied with the guanidinium 1:1 and 3:1 complexes has shown a significant contribution of the hydrogen bonds to the potential barriers hindering the anion reorientations. At low temperatures a proton motion in the hydrogen bond and at 400 K a solid-solid phase transition have been discerned.
Detection of Ar-CH4 Complexes in the 7μm Region by Diode Laser Spectroscopy
Authors: Pak I. , Hepp M. , Roth D.A. , Winnewisser G. , Yamada K.M.T.
Published: February 2015

The absorption spectrum of the Ar-CH4 van der Waals complex was measured for the first time in the 7 μm region. The complexes were produced in a pulsed slit supersonic jet and detected by a tunable diode laser spectrometer with 40 MHz spectral resolution. The strongest absorption features of the Ar-CH4 complex were observed in the spectral region 1310.57-1311.05 cm -1 , located between the Q(l) and the R(0) lines of the ν4 fundamental band of the methane monomer. It was found that the newly detected absorption lines belong to three Q-branches of the Ar-CH4 complex. The transitions of these Q-branches are related to the Q(l) transition in the ν4 fundamental band of the methane molecule, which can rotate almost freely inside the complex. The three Q-branches have been assigned.
Dielectric Studies of a Series of Liquid Crystalline Pyridine Derivates
Authors: Heinemann S. , Kresse H. , Saito S. , Demus D.
Published: February 2015

Measurements of the temperature and frequency dependence of dielectric constants have been performed for five homologues in the range 100 Hz -10 MHz. These substances exhibit a negative anisotropy of the dielectric constants and two relaxation regions (rotation of the molecules around the short resp. long axis) in the investigated frequency range. Even in the crystalline state dipolar reorientations are possible which have been interpreted as rotations of the alkoxy group. Changes of the static dielectric constants, relaxation frequencies and transition entropies are discussed as a measure of structural changes passing the several liquid crystalline phases.
Isolated versus Condensed Anion Structure: the Influence of the Cation Size and Hydrogen Bond on Structure and Phase Transition in MX4
2- Complex Salts. 2,2-Dimethyl-1,3-propanediammonium Tetrabromocadmate(II) Monohydrate, Dimethylammonium Tetrabromozincate(II), and Dimethylammonium Tetrabromocadmate(II)
Authors: Ishihara Hideta , Dou Shi-qi , Horiuchi Keizo , Krishnan V. G . , Paulus Helmut , Fuess Hartmut , Weiss Alarich
Published: February 2015

In the course of work on the anion condensation of Cd and Zn halides, the crystal structures and 79,81 Br NQR spectra of 2,2-dimethyl-1,3-propanediammonium tetrabromocadmate(II) monohydrate (1) and dimethylammonium tetrabromozincate(II) (2), and 79-81 Br NQR spectra of dimethyl-ammonium tetrabromocadmate(II) (3) have been studied. An isolated [CdBr4]2- ion of the salt [H3NCH2C(CH3)2CH2NH3 ]CdBr4 • H2O (1) is formed, with polar orthorhombic space group Pbc21, Z = 4, a = 645.5(3), b = 1628.3(8), c -1389.5(6) pm. [(CH3)2 NH2 ]2ZnBr4 (2) has also an isolated anion lattice, with monoclinic space group, P21 /c, Z = 4, a = 870.6(3), b = 1195.6(4), c = 1628.9(5) pm, β = 121.84(1)°. The 81 Br NQR spectrum of (1) is a quartet (ν in MHz, T = 77 K/ 303 K): ν1 = 68.403/64.278; ν2 = 65.296/62.663; ν3 = 56.525/54.660; V4 = 43.211/45.422. The 81 Br NQR spectrum of (2) is a quartet too (ν in MHz, T= 77 K/300 K): ν1 = 66.848/64.784; ν2= 63.152/ 61.883; ν3 = 57.498/55.890; ν4 = 49.416/50.224. The 81 Br NQR spectrum of [(CH3)2NH2 ]2CdBr4 (3) is also a quartet (ν in MHz, T =77 K/310 K): ν1 = 68.606/67.272; ν2 = 65.806/63.296; ν3 = 58.096/ 57.369; ν4 = 55.757/53.393. The change of NQR frequencies with temperature is smooth for all three compounds. One of the 81 Br NQR lines in both (1) and (2) increases slightly in frequency with increasing T. In the compound (1), the H2O coordinates to NH3
+ groups and to bromines forming a distorted tetrahedron (Br...)2 ...H2O... (... HN)2 , the six angles lying between 69° and 131°. The relations between the bromine NQR and the crystal structures are discussed for the title compounds.
Photoselection of Luminescent Molecules in Anisotropic Media in the Case of Two-Photon Excitation. Part II. Experimental Studies of Hoechst 33342 in Stretched Polyvinyl alcohol) Films
Authors: Kawski A. , Gryczyński Z. , Gryczyński I. , Lakowicz J. R. , Piszczek G.
Published: February 2015

It was found by investigating dichroism and emission anisotropy in the case of one-and two-photon excitation of Hoechst 33342 [bis-benzimide,2,5'-bi-1H-benzimidazole, 2'-(4-ethoxyphenyl)-5-5(4-methyl-1-piperazinyl)] in stretched poly(vinyl alcohol) (PVA) films, that the absorption and fluorescence transition moments lie along the long molecular axis of the molecule studied. The slight deviation of the transition moment direction in fluorescence (about 8°) from that in absorption can be due to the incomplete linearity of the Hoechst molecule.
Notiz: The Dependence of Vicinal Proton-Proton Coupling Constants of Norbomenes on Molecular Structure
Authors: Marković Zoran , Konstantinović Stanimir , Gutman Ivan
Published: February 2015

A modification of the Karplus equation, containing four mutually independent structural terms and five adjustable parameters, is put forward. The new structural factor, introduced into this modification is sin (θ1 + θ2)/2. The new equation reproduces experimental NMR vicinal coupling constants of norbornenes with a standard deviation of about 0.45 Hz.
Monte Carlo Simulation of the Director Field of a Nematic Liquid Crystal with Three Elastic Coefficients
Authors: Gruhn T. , Hess S.
Published: February 2015

In this article, a Monte Carlo simulation is presented, which generates the equilibrium director field of a nematic liquid crystal under the influence of an external field and fixed boundary conditions. The liquid crystal is characterized by a set of directors on a spatially fixed lattice. The simulation is based on an expression for the Frank free energy with three elastic coefficients. The chosen discretisation conserves the nematic symmetry, which means n and - n are equivalent. The results for several Frederiks geometries with homogeneous and spatially modulated external fields are shown, as well as an investigation of a capillary with homeotropic boundary conditions. Further we compare our method with the Lebwohl-Lasher model and introduce an extension of the latter which distinguishes between splay-, twist-and bend-configurations.
Effect of a Tangential Electric Field on the Second Harmonic Resonance in Kelvin-Helmholtz Flow
Authors: Singla R. K. , Chhabra R. K. , Trehan S. K.
Published: February 2015

The stability of Kelvin-Helmholtz flow at the second harmonic resonance between two marginally unstable modes is investigated in the presence of a tangential electric field. We obtain coupled amplitude equations which are examined for the stability characteristics. Numerical integration of the equations reveals that at a certain determinate time, the amplitudes of both the fundamental mode and the second harmonic mode start increasing rapidly, resulting in what is termed as "Explosive Instability". It is demonstrated that for a fluid of given density and dielectric constant, the electric field plays an important role, and the explosive instability sets in much earlier as the electric field increases.
The 2ν5 Overtone Band of Cyanoacetylene by High Resolution FTIR Spectroscopy
Authors: Yamada K. M.T. , Moravec A. , Niedenhoff M. , Bürger H. , Winnewisser G.
Published: February 2015

The 2ν5 overtone band of cyanoacetylene, HCCCN, has been measured with a high resolution FTIR spectrometer. The analysis of the accidental resonances results in very accurate parameters for the observed ν5 = 2 state as well as for the hidden perturber state (ν4 = 1, ν7 = 2); the vibrational energy and the rotational constant have been determined to be 1312.991921(23) cm-1 and 4552.38440(23) MHz for the ν5 = 2 state, and 1310.0627(6) cm-1 and 4572.463(4) MHz for the (ν4 = 1, ν7 = 2) state. The associated hot bands from the ν7 = 1, ν6 = 1, and ν5 = 1 state have also been analyzed.
An ab initio Study of the Molecular Electric-field Gradients of the Chlorsilanes
Authors: Suter H. U. , Maric D. M. , Meier P. F.
Published: February 2015

The electric field gradient (EFG) of chlorine in the chlorine containing silanes (SiCl4 , SiCl3H, SiCl2H2 , and SiClH3) was determined by means of ab initio methods and compared to recent experiments from which nuclear quadrupole moments are extracted. A careful estimation of the AO basis sets and the effect of the electron correlation is undertaken. The results showed the importance of the use of extended basis sets in the calculation of EFGs in second row atoms. Good agreement with deviations less than 5% from the experiments was found. The effect of the electron correlation was found to be small.
Microwave and Millimeterwave Spectrum of 1,1-Difluoroethylene and the Vibrational Mode ν10 from FT-IR Spectroscopy
Authors: Zerbe-Foese H. , Guarnieri A. , Stiefvater O. L.
Published: February 2015

Pure rotational spectra of 1,1-Difluoroethylene (1,1-DFE) in the vibrational ground state (GS) and in excited vibrational states (EVSs) have been investigated by double resonance modulation (DRM) microwave spectroscopy in the range from 12 GHz to 40 GHz, and by millimeterwave spectroscopy in the range from 90 to 260 GHz.

In addition to the GS spectrum, rotational transitions have been observed for the EVSs ν10 = 1, and 2, ν12 = 1, ν6 = 1, ν11 = 1, ν4 = 1, and ν9 = 1. Along with other IR bands up to 1400cm-1 , the fundamental vibrational band ν10 = 1 ← 0 has been observed by FT-IR spectroscopy and has been analysed to yield ν10
0 = 436.8851 cm-1.

Rotational constants and quartic distortion constants were deduced for all observed states. In addition, sextic distortion constants were obtained for the GS and for the EVSs ν10 = 1, 2, ν6 = 1, and ν12 = 1 by computer fits of combined microwave and millimeterwave data to Watson's A-reduced Hamiltonian in Ir representation. The S-reduced Hamiltonian in IIIr representation may be considered more appropriate for the calculation or the fitting of the transitions because 1,1-DFE is a near oblate asymmetric top. Thus, for comparison, results are given for both the A- and the S-reduction.
Determination of the Partial Structure Factors of Amorphous CuZr by Anomalous X-Ray Scattering and Reverse Monte Carlo
Authors: Bionducci M. , Buffa F. , Licheri G. , Navarra G. , Bouchet-Fabre B. , Tonnerre J. M.
Published: February 2015

Anomalous X-ray Scattering experiments have been performed to study the local order in an amorphous CuZr sample prepared by mechanical alloying. The three partial structure factors were extracted both using a regularization algorithm to solve an ill-conditioned system of linear equations and applying the reverse Monte Carlo technique to the experimental data. Then the short range atomic distributions of similar samples prepared by different methods and investigated by different techniques are compared.
The Role of Conjugative Interaction in Stable Carbenes of the 1,2,4-Triazol-5-ylidene Type and their Energy of Dimerization. An Ab Initio Study
Authors: Raabe Gerhard , Breuer Klaus , Enders Dieter , Teles J. Henrique
Published: February 2015

The role of conjugative interaction in stable carbenes of the 1,2,4-triazol-5-ylidene type was studied at different levels of ab initio theory employing model compounds. In the case of parent 4,5-dihydro-1 H-1,2,4-triazol-5-ylidene this type of interaction was found to be of similar importance as in 1,2,4-triazole and pyridine.

Five stationary points were located on the hypersurface of the dimer (C2N3H3)2 . ΔE for all considered dimerization reactions was found to be negative, and the change of energy associated with the formation of the most stable isomer is about -9.5 kcal/mol. In spite of a high value for the singlet-triplet gap of about 90 kcal/mol for the carbene, the heavy atom skeleton of the most stable dimer is close to planarity. This finding is in perfect accordance with the predictions of other authors regarding the geometry of dimers from singlet carbenes stabilized by π-conjugation.
Reaction of Trimethyl-and Dimethyl-Silyl Radicals with Pentamethyldisilane
Authors: Kerst C. , Potzinger P. , Wagner H. Gg.
Published: February 2015

The rate constant for the H atom abstraction of trimethylsilyl radicals from pentamethyldisilane (k(4)) was measured relative to the trimethylsilyl combination reaction k(3). A value for

=(8.53 ± 0.08) · 10-11cm3/2s–1/2 was obtained. For the dimethylsilyl radical, a smaller value for the corresponding rate constant ratio (5.9 ± 0.2) · 10-11 cm3/2 s–1/2 was measured, and this was attributed to a disproportionation reaction between the dimethylsilyl and the pentamethyldisilyl radical leading to dimethylsilylene.
Charge-Transfer Complexes Between Iodine and Substituted Thioureas: Determination of Thermodynamic and Spectroscopic Properties
Authors: Fooken Cornelia , Baumann Wolfram
Published: February 2015

15 iodine complexes with substituted thioureas were investigated in dichloromethane solution by UV-visible spectroscopy, and their equilibrium constants, reaction enthalpies and molar absorption coefficients were determined. The influence of the substituents on the properties of the charge-trans-fer complexes is examined. A critical discussion of previously published data is given, where comparable data are available.
EPR Investigation of VO2+ Ion in [C(NH2)3]3 AIF 6 Single Crystals
Authors: Kasturi T. Lakshmi , Jayaram Geetha , Krishnan V. G.
Published: February 2015

X-band EPR spectra have been recorded at room temperature for VO2+ impurity in single crystals of tris-Guanadiniumhexafluoroaluminate, [C(NH2)3]3 AIF6. 19F super hyperfine structure has been observed on the 51V hyperfine lines. VO2+ replaces Al3+ to form an effective VOF5 complex. There are three possible V-O bond orientations in the AIF6 octahedron but with differing occupancy factors. Bonding parameters have been evaluated.
Enumeration of Chemical Isomers of Polycyclic Conjugated Hydrocarbons with Six-Membered and Five-Membered Rings
Authors: Brunvoll J. , Cyvin B. N. , Cyvin S. J. , Brinkmann G. , Bornhöft J.
Published: February 2015

Polygonal systems P consist of exclusively hexagons and pentagons. They correspond (as chemical graphs) to a certain class of polycyclic conjugated hydrocarbons. This class includes protofullerenes. General formulations for the maximum numbers of internal vertices for P systems with p<6 are derived; here p is the number of pentagons. The CnHs chemical formulas of P systems are studied with special emphasis on the semibuckminsterfullerene (C30H12) , circum-semibuckminsterfullerene (C58H16) and corannulene (C20H10) isomers. Numbers of all CnHs isomers for P systems with r< 6 are computed; here r is the total number of polygons.
EPR Spectroscopy of Some Mn2+ Doped Langbeinites with Regard to Low Temperature Phases
Authors: Böttjer T. , Stockhausen M.
Published: February 2015

Electron paramagnetic resonance (EPR) spectra of Mn2+ centers in 11 langbeinites, A2
+B2
2+ (SO4)3
2-, with A+ = NH4
+, K+, Rb+ or Tl+ and B2+ = Mg2+, Ca2+, Zn2+ or Cd2+, are measured over relatively large temperature ranges chosen to cover phase transitions, if any. For 7 langbeinites which do not contain Mg2+, phase transitions are observed, but no more than one low temperature phase is distinguishable by EPR. Except for the K-Zn langbeinite, only one defect center is noticeable in that phase. The low temperature EPR parameters are reported, and their temperature dependence is discussed with respect to correlations between structure and phase transition characteristics and to the trigger mechanism.
Methane as Carrier Gas for Molecular Beam Microwave Spectroscopy to Observe Transitions of Higher Rotational Energy Levels
Authors: Lorenzo F. , Grabow J.-U. , Dreizler H.
Published: February 2015

We report on an observation in molecular beam rotational spectroscopy: using Methane rather than rare gases as carrier extends the range of observable transitions towards levels of higher rotational energy.
The 33S Nuclear Quadrupole Coupling in the Rotational Spectrum of anti-2,3-Dimethylthiirane
Authors: Grabow Jens-Uwe , Dreizler Helmut
Published: February 2015

The rotational spectrum of 33S anti-2,3-dimethylthiirane with its 33S nuclear quadrupole coupling hyperfine structure in the range 7.6 to to 21.5 GHz and its analysis is reported. The rotational constants are A = 5331.1401(5), B = 3506.3963(10), and C = 2356.9273(2) MHz. The 33S quadrupole coupling constants are χaa = 8.3871(93), χbb = -32.3291(174), and χcc = 23.9420(174) MHz.
EPR Studies of Cr3+ and Fe3+ in Host Crystals with Langbeinite Structure
Authors: Kastner J. , Mosel B. D. , Müller-Warmuth W.
Published: February 2015

Electron paramagnetic resonance (EPR) spectra of trivalent chromium and iron ions have been investigated in host crystals of double sulfates with langbeinite structure, A2B2(SO4)3 , with A = NH4
+, Rb+, Tl+ and B = Cd2+, Mg2+. In most cases, single crystals could be grown, and the spin Hamiltonian parameters have been determined from the rotational diagrams. Powder spectra were analyzed and simulated as well. Three centres of axial symmetry with different zero field splittings have been observed for Cr3+, and two for Fe3+. The trivalent impurity ions have been shown to occupy divalent lattice sites substitutionally, but the environments are different depending on the structure and the mechanism of charge compensation. A qualitative description of the incorporation of dopants has been possible on this basis, taking into account the local relaxation and the ligand field stabilization effects. Temperature dependent single crystal and powder measurements have provided information on the zero field splitting and phase transitions.
Dissociation of Slow Polyatomic Molecules by Grazing Scattering at Surfaces
Authors: Schmidt L. , Popova A.M. , Komarov V.V. , Jungclas H.
Published: February 2015

We consider polyatomic molecules containing peripheral chains of valence groups, which slide along crystallic surfaces at grazing incidence. The periodically located Coulomb centres of the crystallic surfaces interact with the moving valence group dipoles like a time-dependent oscillation potential. This interaction can lead to multiple resonant vibrational excitations of the peripheral valence group dipoles. Accumulation of such collective excitations in the valence group chains (excimols) eventually can lead to the cleavage of particular bonds (trap bonds) inside the molecule. A model for this complex process is presented including a parameterised formula for the dissociation probability of polyatomic molecules scattered by a surface at grazing incidence. The model is supported by the experimental observation of dissociation energy thresholds.
Photoluminescence Properties of trans–4,4'–Diamino–stilbene in Poly(vinyl alcohol) Films
Authors: Kawski A. , Kubicki A. , Kukliński B. , Nowosielski T.
Published: February 2015

Experimental studies have shown that the nonpolar molecule 4,4'-diamino-stilbene (DAS) in poly(vinyl alcohol) film (PVA) at 296 K, apart from fluorescence displays phosphorescence whose intensity differs only slightly from that observed at 84 K. The overlapping of fluorescence and phosphorescence bands is the reason of the unusual behaviour of the emission anisotropy in the longwave absorption and photoluminescence bands. A distinct effect of direct irradiation on the intensity of these bands was observed.
Pattern Formation in Force-free Magnetic Fields and Beltrami Flows
Authors: Qing-Zeng Feng
Published: February 2015

Force-free magnetic fields and Beltrami flows, which are selenoidal vector fields and satisfy the condition that the field vector is everywhere parallel to its curl, have complex topological structures and usually show chaotic behavior. The lines of force are determined by the equations of a 3-D (dimensional) dynamical system. In the integrable case, all lines of force lie on some families of tori. If the integrable solution undergoes a small perturbation, most of the original tori still exist but undergo a slight distortion (KAM tori). Near the original heteroclinic cycles emerges a chaotic layer. By superposition of the basic solutions of force-free magnetic fields one can get very complicated pictures: a single line of force could be space filling within some subspace of a 3-D region, which has a fractional dimension and a positive Lyapunov exponent, i.e. one gets a chaotic line of force or a fractal. At the same time there are still ordered regions in the chaotic surroundings. Tubes of force which are tangled or self-knotted embed in the chaotic sea. The KAM tori can also be disrupted through resonances, leading to increased chaotic regions. Thus, the effect of nonlinear dynamics plays an important role in the pattern formation of force-free magnetic fields and Beltrami flows.
The Critical Amplitude for Bifurcation Points of the Logistic Map
Authors: Tsuchiya Takashi
Published: February 2015

The phenomenon called critical slowing down is studied for some analytically tractable bifurcation points of the logistic map. The critical amplitude and the critical amplitude ratio are introduced to describe the critical behaviors more precisely when the critical exponents are identically unity for two critical behaviors which are to be compared. Since Hao predicted unity of the critical exponent for 1-d maps assuming exponential damping of the distance from the attractor, the assumption is checked. The result is that the shrinkage of the valid region of the assumption occurs as the adjustable parameter approaches one of the bifurcation points.
The ‘‘Triptych” Function -Determining the Basins of Attraction of One-Dimensional Maps
Authors: Moreira I. C.
Published: February 2015

We show that a modification of the path length method, introduced by R. Richter et al. [Z. Naturforsch. 49 a, 871 (1994)], gives us a method for finding basins of attraction of one-dimensional maps with multiple attractors.
A Diffraction Study of Amorphous Si0.40C 0.24N0.36
Authors: Uhlig H. , Frieß M. , Dürr J. , Bellissent R. , Lamparter H.-P. , Aldinger F. , Steeb S.
Published: February 2015

In the present work, amorphous Si0.40C0.24N0.36 samples were investigated. X-ray and neutron diffraction experiments were performed, in order to evaluate the structure factors by the method of contrast variation. The structure can be described as crosslinked Si-N-C matrices. Within these matrices SiN4 tetrahedra are predominant. Direct Si-Si contact does not occur. We report on the short range order and the nature of chemical bonding.
Study of Orientational Order of Liquid Crystal 8 OCB Doped with Perylene-like Dyes by Means of Polarized Optical Spectroscopy
Authors: Bauman Danuta , Wolarz Eryk
Published: February 2015

Measurements of the polarized absorption and fluorescence spectra for perylene-like dyes dis-solved in a liquid crystal 8 OCB have been used to study the long-range orientational order in the smectic A and nematic phases. The temperature dependence of the order parameters  and  has been investigated and the orientational distribution function has been determined. On the basis of the experimental order parameter values some information about the orientation of molecules in guest-host mixtures has been obtained.
Dielectric Investigations in Smectic B-Phases
Authors: Heinemann S. , Kresse H. , Urban S. , Dabrowski R.
Published: February 2015

Several liquid crystalline substances exhibiting SB -phases have been investigated by dielectric and calorimetric measurements. Special attention is taken to the low frequency relaxation process at the phase transition nematic-SB . From the large change of relaxation frequencies, crystallinity of the SB -phases has been concluded. Nevertheless, motion is still present and not frozen.
Isolated versus Condensed Anion Structure II; the Influence of the Cations (1,3-propanediammonium, 1,4-phenylendiammonium, and n-propylammonium) on Structures and Phase Transitions of CdBr2-
4Salts A 79,81Br NQR and X-ray Structure Analysis
Authors: Ishihara Hideta , Dou Shi-qi , Horiuchi Keizo , Krishnan V. G. , Paulus Helmut , Fuess Hartmut , Weiss Alarich
Published: February 2015

The influence of the cations on the condensation of anions CdBr4
2- in salts (A')CdBr4 (II) and (A)2CdBr4 (II) is studied by 79,81Br NQR and X-ray crystal structure determinations. (A')CdBr4 : A' = [H3N(CH2)3NH3]2+ (1) crystallizes with a layer-type anion structure at 298 K and A' = [1,4-(H3N)2C6H4]2+ (2) crystallizes with a chain-type anion structure at 298 K. (A)2 CdBr4 : A = [n-H3C(CH2)2NH3]+ (3) crystallizes with a layer-type anion structure at 293 K. (1) shows successive phase transitions at 328, 363, and 495 K according to the NQR and DSC measurements. Phase IV of (1): at 298 K orthorhombic, Pnma, Z = 4,a = 772.1 (4), b = 1905.4(9), c = 789.8(4) pm. 81Br NQR spectrum showed a doublet at 77 K (phase IV) with ν1= 61.177 and ν2 = 45.934 MHz and also a doublet at 350 K (phase III) with ν1= 57.581 and ν2 = 48.747 MHz. (2): at 295 K orthorhombic, Pnma, Z = 4, a = 802.5(3), b = 1775.1(6), c = 881.9(3) pm; the five-coordinated Cd atom and one-dimensional [CdBr4]2- anion chain structure was observed. This coordination and chain structure are very rare for (A')CdX4 (II) or (A)2CdX4 (II). Two 81Br NQR lines were observed at 77 K: ν1= 70.159 and ν3 = 40.056 MHz. One more line appeared at 85 K: ν2 = 53.622 MHz. A 81Br NQR triplet was observed at 273 K: ν1 = 67.919, ν2 = 56.317, and ν3 = 40.907 MHz. (3) shows successive phase transitions at 121, 135, 165, and 208 K according to the NQR, DSC, and DTA measurements. Phase I of (3): at 293 K orthorhombic, Cmca, Z = 4, a = 783.4(4), b = 2480.2(10), c = 806.5(4) pm. 81Br NQR doublet was observed at 77 K (phase V) and at 300 K (Phase I) with ν1 = 61.060 and ν2 = 54.098 MHz (77 K); v1 = 55.835 and ν2 = 55.964 MHz (373 K). No NQR line could be observed in phases II, III, and IV.
A Comparison of Strategies for Obtaining High-Resolution NMR Spectra of Quadrupolar Nuclei
Authors: Youngman R. E. , Werner-Zwanziger U. , Zwanziger J. W.
Published: February 2015

A comparison of high-resolution NMR methods for quadrupolar nuclei is presented. The samples studied are pure and modified boron oxide glasses, and the boron NMR spectra are recorded using three different experiments capable of high resolution: Double Rotation, Dynamic Angle Spinning, and Multiple-Quantum Magic Angle Spinning. Resolution of the similar ring and nonring boron sites in these glasses, in the presence of disorder, provides a realistic study of the strengths and limitations of these experiments. Conclusions about the relative applicability of these experiments in different situations are presented.
Multidimensional NQR: Imaging and Exchange Spectroscopy
Authors: Kimmich Rainer
Published: February 2015

In this context a ‘‘dimension’’ can be of a spatial or of a spectroscopic nature. In the last two decades, multidimensional nuclear magnetic resonance and imaging have proven to be most useful tools for the investigation of materials. It turned out that some of these measuring principles can be applied to zero-field NQR as well. The purpose of this presentation is to elucidate two-dimensional exchange spectroscopy and imaging procedures suitable for NQR and to outline potential applications.
Enhanced Information Recovery in 2D On-and Off-Resonance Nutation NQR using the Maximum Entropy Method
Authors: Maćkowiak Mariusz , Kątowski Piotr
Published: February 2015

Two-dimensional zero-field nutation NQR spectroscopy has been used to determine the full quadrupolar tensor of spin - 3/2 nuclei in serveral molecular crystals containing the 3 5 Cl and 7 5 As nuclei. The problems of reconstructing 2D-nutation NQR spectra using conventional methods and the advantages of using implementation of the maximum entropy method (MEM) are analyzed. It is shown that the replacement of conventional Fourier transform by an alternative data processing by MEM in 2D NQR spectroscopy leads to sensitivity improvement, reduction of instrumental artefacts and truncation errors, shortened data acquisition times and suppression of noise, while at the same time increasing the resolution. The effects of off-resonance irradiation in nutation experiments are demonstrated both experimentally and theoretically. It is shown that off-resonance nutation spectroscopy is a useful extension of the conventional on-resonance experiments, thus facilitating the determination of asymmetry parameters in multiple spectrum. The theoretical description of the off-resonance effects in 2D nutation NQR spectroscopy is given, and general exact formulas for the asymmetry parameter are obtained. In off-resonance conditions, the resolution of the nutation NQR spectrum decreases with the spectrometer offset. However, an enhanced resolution can be achieved by using the maximum entropy method in 2D-data reconstruction.
Fast ρ-NQR Imaging with Slice Selection
Authors: Robert H. , Pusiol D. J.
Published: February 2015

A combination of a new pulse sequence allowing fast data acquisition in the rotating frame version of NQR (ρ-NQRI) together with a method for slice selection, is reported. The procedure allows us to record the magnetization evolution during its motion in the rotating frame. At the same time a zero-crossing external magnetic field gradient is applied in order to select a determined slice of the object to be imaged. The experiments reported are the first steps toward a fast tridimensional ρ-NQRI; even more, as the spectroscopic information is preserved during the spatial encoding procedure, it could be considered as a 3D spatially resolved NQR spectroscopy technique.