bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen-14 NQR in s-Triazine Derivatives
Authors: Péneau A. , Manallah B. , Guibé L.
Published: February 2015

Within a study of the temperature dependence of NQR frequencies in some s-triazine derivatives [1], resonance frequencies at 4.2 K were determined in melamine, cyanuric acid, and cyanuric chloride. New lines, which were not reported so far, were detected in two of these compounds. In melamine, nine more lines were found as already described in [4], In cyanuric chloride, two more lines were found showing a second nitrogen site, in agreement with the existence of two chlorine NQR sites in this compound.
81Br and 27Al NQR of AlBr3 · 2C5H5N, AlBr3 · 1.5CH3CN, and AlBr3 · 2CH3CN
Authors: Yamada Koji , Okuda Tsutomu , Negita Hisao
Published: February 2015

81Br NQR was studied in AlBr3 · 2C5H5N, AlBr3 · 1.5CH3CN, and AlBr3 · 2CH3CN. From the NQR spectra it is apparent that the solid compounds are build up by ion pairs [AlBr2(C5H5N )4
+, AlBr4
-], [Al(CH3CN)6
3+, 3AlBr4
-], and [AlBr(CH3CN)5
2+, 2AlBr4
-- CH3CN], respectively. 27Al NQR detected by SEDOR technique supports these structural models. Using these NQR parameters, the metal-ligands interactions in the six-coordinated complexes is discussed on the basis of the donor strength. In the case of AlBr3 ·2CH3CN two types of reorientational motion of the AlBr4
- tetrahedra were detected from the spin lattice relaxation times and from fade-out phenomena of the 81Br NQR signals.
Halogen NQR Studies in Certain Mercuric Halide-Polyether Complexes
Authors: Indumathy S. , Sridharan K. R. , Ramakrishna J. , Wulfsberg G.
Published: February 2015

The temperature variation of 35Cl and 81Br NQR frequencies are reported for mercuric chloride · triethylene glycol dimethyl ether (HgCl2 · triglyme), mercuric chloride · diethylene glycol dimethyl ether (HgCl2 · diglyme), and mercuric bromide · diethylene glycol dimethyl ether (HgBr2 · diglyme). The frequencies have been assigned to the appropriate halogens using molecular models which take into account the various intra- and inter-molecular interactions in the solid state. The observed temperature variation of the NQR frequencies, in the range 77 -300 K. has been analysed using the two torsional mode analysis in the framework of the Bayer-Kushida-Brown method with Tatsuzaki’s correction to obtain the torsional frequencies and their average temperature coefficients.
Deuterium and Sodium Quadrupole Interactions in Sodium Hydroxide. The Monoclinic Phase
Authors: Amm D. T. , Segel S. L. , Bastow T. J. , Jeffrey K. R.
Published: February 2015

The temperature dependence of the 23NaOH Pure Quadrupole Resonance Frequency has been studied from 77 K to 550 K and shows a change in slope and a discontinuous change in frequency of 6 ± 2 kHz at the orthorhombic to monoclinic phase transition at 505 K At 292 K the 23Na NQR frequency is 1.778 ± 0.001 MHz, η < 0 .04. The temperature dependence of the deuterium quadrupole coupling was fit to a librating molecule model between 293 K and 570 K (QCC = 245 ± 2 kHz, η = 0.05 ± 0 .0 1 at 293 K) and confirms that the frequency of the libration decreases in the high temperature monoclinic phase. X-ray studies indicate that down to 10 K there are no further phase transitions in NaOH. On the other hand, it is now known that NaOD, orthorhombic at room temperature, monoclinic at high temperature, suffers another transition at 160 K to yet another monoclinic phase.
Pressure Dependence of Chlorine NQR in Strontium Chlorate and Barium Chlorate Monohydrate
Authors: Krishnan V. , Krishna Moorthy T. V. , Ramakrishna J.
Published: February 2015

The pressure dependence of the 35Cl-NQR frequencies in barium chlorate monohydrate and strontium chlorate, has been investigated up to 7000 kg cm-2. Ba(ClO3)2 · H2O shows a single 35Cl-NQR line at 29.337 MHz (T = 297 K, p = 1 bar). ν(35Cl) increases linearly with pressure in the range studied, with (1/ν )(∂ν/∂p)T = + 0.409 x 10-6 kg-1 cm2 which is much smaller than observed in NaClO3 and KCIO3. Sr(ClO3)2 also gave a single 35Cl-NQR frequency at 20.105 MHz (T = 297 K, p = 1 bar). The pressure dependence is very small and negative in this case. The data in both cases have been analysed to obtain the volume dependence of the torsional frequency. It is pointed out that explicit pressure effects on the electric field gradient have to be taken into account to provide an explanation for the observed pressure dependence of ν (35Cl).
Nuclear Quadrupole Resonance Studies in MICA
Authors: Sengupta S. , Rhadakrishna S. , Marino R. A.
Published: February 2015

Aluminum-27 NQR transitions were detected in Muscovite Mica at room temperature using double resonance by level crossing (DRLC) techniques. Three lines were observed with frequencies of 572.5, 1052.0, and 1624.5 kHz. These lines are assigned to the octahedrally coordinated site, AlO4(OH)2. The corresponding quadrupole coupling constant, e2q Q/h, and asymmetry parameter, η, are 3554.8 kHz and 0.265, respectively. The remaining tetrahedrally coordinated sites, AlO4, gave no discernible signal, perhaps due to the greater 27Al- 1H distance.
The Temperature Dependence of the N-14 NQR Spectrum, Relaxation Times, and Line Shapes of Cyanuric Fluoride
Authors: Stutz Conley , Garcia Kevin , Cochran Stephanie
Published: February 2015

Measurements of the N -14 NQR spectrum, relaxation times, and line shapes as functions of temperature of cyanuric fluoride are reported. This material exhibits very wide lines and thus lends itself to determining the profile of the lines from measurements of the echo heights. The material also exhibits a phase transition similar to that found in s-triazine. The phase transition occurs at 115 ± 5 K. A comparison of the results is made with those obtained previously for cyanuric chloride and s-triazine.
Microprocessor-Controlled Pulsed NQR Spectrometer for Automatic Acquisition of Zeeman Perturbed Nuclear Quadrupole Spin Echo Envelope Modulations (ZSEEM )
Authors: Reddy Narsimha , Bhavsar Arun , Narasimhan P. T.
Published: February 2015

A simple microprocessor-controlled pulsed NQR spectrometer system has been developed with the capability to acquire Zeeman perturbed spin echo envelope modulations (ZSEEM). The CPU of the system is based on the Intel Corporation 8085 A microprocessor. The performance of the spectrometer is illustrated with the presentation of ZSEEM spectra of NaClO3 and KClO3.
Elektronenspektren der Fluoro-Chloro-Osmate(V), [OsFnCl6–n]–, n = 0 — 6
Authors: Groth Th. , Preetz W.
Published: February 2015

The electronic absorption spectra of the solid tetraethylammonium salts of [OsFnCl6-n]- are measured at 10 K. The strong bands in the UV/YIS region are assigned to charge transfer transitions from π(t1 u, t2 u) and σ(t1 u ) Cl orbitals into the π(t2g
3) Os(V) level. The weak intraconfigurational excitations within the t2g
3 manifold of Os(V) are split by spin-orbit coupling and lowered symmetry into Kramers doublets, observed in the range 5500-18000 cm-1. The 0 - 0-transitions are deduced from vibrational fine structure; for the centrosymmetric complexes they are confirmed by hot bands recorded in the normal temperature spectra. There is a systematical shift of all absorption bands to higher energy with increasing number of F-ligands.
On the Induced Optical Activity of Triphenylmethane Dyes
Authors: Gawroński Jacek , Koput Jacek , Wierzbicki Andrzej
Published: February 2015

INDO/S calculations applied to the skewed benzaurin chromophore reveal large rotational strength associated with the lowest electronic excited states. The calculated oscillator and rotational strengths are compared with the experimental data for induced optical activity of sulphonephthalein-cinchona alkaloid complexes.
A physical Study on the Aromaticity of 4H-Pyran-4-one, 9H-Xanthen-9-one, and related sulphur Compounds
Authors: Lumbroso Henri , Curé Jacqueline , Evers Michel
Published: February 2015

Dipole moment analysis of 4H-pyran-4-one and 9H-xanthen-9-one, and their sulphur analogues, and of 9H-selenoxanthen-9-one, enables a discussion on their aromaticities. In the present work, the dipole moments of tetrahydro-4H-pyran-4-one, tetrahydrothio-4H-pyran-4-one, tetrahydroseleno- 4H-pyran-4-one, 9(10H)-anthracen-9-one, 9H-xanthen-9-one, 9H-thioxanthen-9-one and 9H-selenoxanthen-9-one were measured in benzene solution at 30.0 °C.
Nitrogen and Chlorine Hyperfine Structure in the Rotational Spectra of 4-Chloropyridine
Authors: Heineking N. , Dreizler H.
Published: February 2015

We resolved and analysed the 14N hyperfine structure in addition to the 35Cl and 37Cl hyperfine structure of 4-chloropyridine-[35Cl] and -[37C1] to investigate substitutional effects.
Nitrogen-14 Nuclear Quadrupole Coupling and Centrifugal Distortion of Pivalonitrile
Authors: Fliege Eckhard , Dreizler Helmut , Cox A. Peter
Published: February 2015

The rotational transitions J' - J" = 1 - 0 , 2 - 1 , 3 - 2 , and 4 - 3 of pivalonitrile have been measured in the frequency range of 5 - 2 2 GHz with a microwave Fourier transform spectrometer. The 14N nuclear quadrupole coupling constant, e q Q, as well as the centrifugal distortion parameters, DJ and DJK, have been determined to be: e q Q = - 4.221(15) MHz; DJ = 0.349(56) kHz, DJK = - 3.68(15) kHz. The rotational constant B0 was fixed with high precision: B0 = 2749.9093(13) MHz. Nitrogen-14 quadrupole coupling in pivalonitrile is compared with that in other cyano compounds.
MD-Simulation of Molten (Li, K)Cl at the Eutectic Composition. Self-Exchange Velocities of Li- and K-Isotopes near the Cl--Ions
Authors: Okada Isao
Published: February 2015

Molecular dynamics simulation (MD) has been done for a molten (Li, K)Cl mixture of the eutectic composition at about 700 K, 950 K and 1100 K and, for comparison, also for pure LiCl and KCl at about 950 K and 1100 K The atomic masses of half the Li+ and K+ ions have been set at 6.941 and 39.098, respectively. Self-exchange velocities (SEV’s) of these cations have been calculated. The Chemla effect is reflected by the SEV’s. The isotope effects of the SEV’s in the mixture increase slightly with temperature. The motions of the cations with respect to the adjacent CI- are classified into four modes: (1) an oscillating motion, (2) a leaving motion, (3) a wandering motion and (4) a coming-back motion. It is found that the velocity of the leaving motion is dependent only on the masses and the temperature, and independent of the kind of cations and the composition.
The Millimeter- and Submillimeter-Wave Spectra of Acetaldehyde: Centrifugal Distortion and Internal Rotation Analysis
Authors: Maes H. , Wlodarczak G. , Boucher D. , Demaison J.
Published: February 2015

141 internal rotation doublets (282 transitions, among which 174 new measurements) of acetaldehyde in its ground torsional state have been measured up to 600 GHz (J ≦ 32). An overall fit of the measurements (including the lines identified by previous workers) using the Internal Axis Method has allowed us to accurately determine the rotational, centrifugal distortion and internal rotation constants. The quality of the fit is good enough to permit the accurate prediction of transition frequencies of possible astrophysical interest.
Evaluation of Partition Functions of Triatomic Molecules Using Data Obtained by ab initio Calculations — Sums of States of Molecules with Spatially Degenerate Lowest Electronic States
Authors: Radić-Perić Jelena , Perić Miljenko
Published: February 2015

The evaluation of partition functions of triatomic molecules based on data obtained by means of the ab initio method is discussed. Special attention is paid to molecules exhibiting the Renner- Teller effect. Various approximate approaches for the calculations of partition functions are explicitly considered. The results are shown for HNF, NCO and BH2.
Number of Kekule Structures of Systems with Repeated Units
Authors: Cyvin S. J. , Cyvin B. N. , Gutman I.
Published: February 2015

Combinatorial formulas are derived for the number of Kekulé structures of conjugated (benzenoid) systems composed of repeated, mutually condensed units.
Diode-Laser Study of Rotational Temperature and Absorption Line Shape in Supersonic Free Jets
Authors: Wallraff P. , Yamada Koichi M. T. , Winnewisser G.
Published: February 2015

Infrared spectra of NNO and OCS have been studied in a supersonic free jet by using a diodelaser spectrometer. The sample gas of the molecules of 1 bar pressure was injected into a vacuum chamber (p ≈ 10−5 mbar) through a nozzle with a magnetic valve. The molecular beam was pulsed ( ≈ 82 Hz) by controlling the magnetic valve. Near the nozzle and for low values of the quantum number J the rotational temperature was determined to range between 29 and 3 K. For NNO we have observed the unusual line shapes in detail. They are caused by superposition of absorption signals of molecules in the jet and the background.
Esters of (S)-1,2-propanediol and (R,R)-2,3-butanediol — Chiral Compounds Inducing Cholesteric Phases with a Helix Inversion ·
Authors: Heppke G. , Lötzsch D. , Oestreicher F.
Published: February 2015

Mesogenic chiral esters of optically active (S)-1,2-propanediol and (R,R)-2,3-butanediol were synthesized. The compounds, added to a nematic phase induce cholesteric phases exhibiting a helix inversion with temperature variation. This effect is independent of the molecular structure of the nematic solvent. The inversion temperature varies only slightly with concentration but can be influenced by the mesogenic substituent.
The Photoelectron Spectra of 1,3-Diphenyl-2-pyrazolines
Authors: Klessinger M. , Srzić D. , Kovač B. , Klasinc L.
Published: February 2015

The PE spectra of eight 1,3-diphenyl-2-pyrazolines and a 1,3-diphenyl-tetrahydro-1,2-diazine are reported. The low energy of the first Ei of this class of compounds as well as the effect of electron donor or acceptor substituent in the para positions of any of the phenyl groups are discussed on the basis of a simple MO model.
MINDO-Forces Study of Phenyl and Cyclopropyl Substituted Allyl Cations and Anions
Authors: Jarjis Hayfa M. , Khalil Salim M.
Published: February 2015

MINDO-force calculations have been performed on phenyl and cyclopropyl substituted allyl cations and anions with complete energy minimization. It is found that the phenyl ring destabilizes the allyl cations when substituted at the terminal and at the center carbon atom of the cation, while the cyclopropyl ring stabilizes the allyl cation when substituted at the terminal carbon atoms, but destabilizes the cation when substituted at the center carbon atom of the cation. These results agree with the experimental ones. In the case of the allyl anions, it is found that the phenyl ring destabilizes the allyl anions when substituted on the terminal and on the center carbon atoms of the allyl anions, while the cyclopropyl ring stabilizes the allyl anion when substituted on the terminal carbon atom but destabilizes the anion when substituted on the center carbon atom. Also, it is found that both the phenyl and cyclopropyl rings are electron withdrawing when substituted on the allyl anions, while they are electron donating when substituted on the allyl cations.
Analogues to a Julia Boundary Away from Analyticity
Authors: Kahlert Claus , Rössler Otto E.
Published: February 2015

Dedicated to Prof. Ernst Bayer on the occasion of his 60th birthday

An analyticity-destroying term is introduced into the complex logistic map. Two types of selfsimilar basin boundaries are found, one a “coastline-type” direct analogue to Julia's, the other a locally smooth boundary that nevertheless is more complicated than the well-known “striated” fractal basin boundaries of Grebogi et al.
Densities and Molar Excess Volumes of Molten (Alk, Ag)Br- and (Alk, Ag)I - Mixtures
Authors: Boßmann E. , Müller M. , Richter J.
Published: February 2015

Measurements of densities (and from these molar excess volumes) of the molten salt systems (K,Ag)Br, (Na,Ag)Br, (Rb.Ag)Br, (Cs.Ag)Br, (Na,Ag)I, (K,Ag)I, and (Cs,Ag)I as functions of composition and temperature from the liquidus curve up to 1200 K are reported.
Raman-Spektren der Hexaselenidohypodiphosphate des Mg, Ca und Ba
Authors: Pätzmann Ulrich , Brückner Wolfgang
Published: February 2015

The Hexaselenidohypodiphosphates Mg2P2Se6, Ca2P2Se6 and Ba2P2Se6 have been prepared and their Raman spectra recorded. The observed frequencies of Mg2P2Se6 are assigned on the basis of P2Se6
4- units with D3d symmetry, while these of the Ca and Ba compound show symmetry splitting (assignment with C2h symmetry).
Molecular Beam Laser Saturation Spectroscopy
Authors: Geisen H. , Krümpelmann T. , Neuschäfer D. , Ottinger Ch.
Published: February 2015

Laser saturation spectroscopy on particle beams is demonstrated as a new sub-Doppler technique. It offers unique advantages regarding resolution and intensity.
Stationary Solutions of Incompressible Stokes Equation for a Circular Pipe
Authors: Heil M.
Published: February 2015

Stationary modes of the incompressible Stokes equation are derived using the method of potentials. Their relation to instationary modes is discussed.
Chaotic Dynamical Systems as Automata
Authors: McCauley Joseph L.
Published: February 2015

We discuss the replacement of discrete maps by automata, algorithms for the transformation of finite length digit strings into other finite length digit strings, and then discuss what it required in order to replace chaotic phase flows that are generated by ordinary differential equations by automata without introducing unknown and uncontrollable errors. That question arises naturally in the discretization of chaotic differential equations for the purpose of computation. We discuss as examples an autonomous and a periodically driven system, and a possible connection with cellular automata is also discussed. Qualitatively, our considerations are equivalent to asking when can the solution of a chaotic set of equations be regarded as a machine, or a model of a machine.
Elektronische und Resonanz-Raman-Spektren der Chloro-Bromo-Ruthenate(IV), [RuClnBr6-n]2-, n = 0 ... 6
Authors: Allwörden H. N. v. , Preetz W.
Published: February 2015

The vibrational and electronic resonance Raman spectra of the solid tetraalkylammonium salts of [RuClnBr6-n]2-, n = 0 . . . 6, are measured at 80 K. The observed electronic Raman bands in the regions of 640-740 cm-1 and 1560-1790 cm-1 are assigned to the intraconfigurational transitions Γ1 → Γ4 and Γ1 → Γ3, Γ5 within the 3T1g(Oh) ground term. The observed splittings and shifts, due to spin orbit coupling and lowered symmetry, are interpreted qualitatively according to the point groups D4h, C4V, C3V and C2V. The O-O-transitions are deduced from vibrational fine structure. The electronic Raman bands of [RuCl6]2- and [RuBr6]2- are assigned in detail by polarisation measurements.
Raman-Studies of the Organic Superconductor β-(BEDT-TTF)2IAuI
Authors: Świetlik R. , Grimm H. , Schweitzer D. , Keller H. J.
Published: February 2015

The resonance Raman spectra of (IAuI)--anions in the organic superconductor β-(BEDTTTF)2IAuI as well as in the electrolyte salt n-Bu4AuI2 are investigated. In contrast to β-(BEDT-TTF)2I3 in the crystals of β-BEDT-TTF)2IAuI at low temperature only one Raman line at 120 cm-1 corresponding to the symmetrical stretching mode of the (IAuI)--anion is observed. No distinct change in the Raman spectra is observed at the superconducting transition.
On the Determination of Transition-Moment Directions from Absorption Anisotropy Measurements
Authors: Kawski A. , Gryczyński Z.
Published: February 2015

A formula is derived for the absorption anisotropy K = (A∥ - A⊥) / (A∥ + 2A⊥ ) (where A∥ and A⊥ are the absorbances parallel and perpendicular to the stretching direction of the polymer film, respectively) as a function of the stretch ratio, Rs, of the film and the angle φ between the absorption transition moment direction and the long axis of a prolate molecule. Employing this relation, absolute transition moment directions (the angles φ) were determined experimentally for the following compounds: 1.8-diphenyloctatetraene (DPO), 1,6-diphenylhexatriene (DPH), 1.4-diphenylbutadiene (DPB), 4-dimethylamino-4'-nitrostilbene (DNS), 4-dimethylamino- 4'-chlorostilbene (DCIS) and p-terphenyl (TP). The directions were found to be along the long molecular axis in the long-wave absorption band. Small deviations of the angles obtained from (φ= 0°, which were of the order of several degrees, are due to the incomplete linearity of the molecules under investigation.
An Intuitive Understanding of Black-Hole Evaporation by Viewing it in Terms of More Familiar Quantum-Field Effects in Flat Spacetime
Authors: Nugayev R. M.
Published: February 2015

The article is aimed at an intuitive understanding of the recently explored deep connections between therm al physics, quantum field theory and general relativity. The physical effects involved in particle creation by a black hole are viewed in terms of more familiar quantum -field effects in flat spacetime. Black hole evaporation is investigated in terms of temperature correction to the Casimir effect. T he application of the Casimir effect results and those for accelerated mirrors reveals that a black hole should produce the blackbody radiation at a temperature that exactly coincides with Hawking’s result. Its blackbody nature is due to the interaction of virtual positive-energy particles with the surface of a “cavity” formed by the Schwarzchild gravitational field potential barrier. The virtual particles are “squeezed out” by the contraction of the potential barrier and appear to an observer at J+ as the real blackbody ones.
Band Structure Calculations of Two-Dimensional (2 D) Models of the Phases LiBC and CaAl2Si2
Authors: Ramirez Rafael , Nesper Reinhard , Schnering Hans Georg von , Böhm Michael C.
Published: February 2015

The electronic structures of the phases LiBC and CaAl2Si2 have been investigated by two dimensional crystal orbital calculations. The corresponding solid-state ensembles have been separated into anionic (e.g. [BC]-, [AlSi]- , [Al2Si2]2-) and cationic substructures. The employed fragmentation is topologically related to the electron counting schemes used in the classical Zintl approach. The band structures of the anionic fragments have been determined by a semiempirical Hartree-Fock crystal orbital (CO ) Hamiltonian on the basis of the tight-binding approximation. The adopted self-consistent-field variant is an intermediate neglect of differential overlap (INDO ) scheme. The influence of the cationic substructure has been simulated by an electrostatic point-charge model. The computational formalism allows for a suitable explanation of the conformations of the anionic subunits of the studied solids. In the CaAl2Si2 model the site symmetry in the anionic substructure has been studied in larger detail. The Al atoms show a tetrahedral coordination while an inverted tetrahedron (i.e. umbrella-like structure) is realized at the more electronegative Si centers. This local geometry is stabilized by the Coulomb interaction between the anionic [Al2Si2]2- layer and the cationic substructure. The energetic sources leading to the different conformations in LiBC and CaAl2Si2 are also quantified. The observed geometric preferences are rationalized by means of an energy fragmentation into covalent resonance (kinetic energy of the electrons) and classical Coulomb elements. This energy decomposition in the planar and chair-like conformations of LiBC and CaAl2Si2 shows that the kinetic energy favours the former, the electrostatic part the latter conformation. The dimerization of two anionic substructures (CaAl2Si2 structure) is also studied by the tight-binding formalism . The observed geometric differences between intra- and interlayer bonds are satisfactorily reproduced by the semiempirical CO model.
Zur spektroskopischen Analyse von Reaktionen zweiter Ordnung
Authors: Mauser Heinz
Published: February 2015

In the first part of this work [1] it was shown that it is possible to analyse kinetically uniform reactions of second order using only spectroscopic methods. No knowledge of the coefficients of extinction is needed. Now systems are discussed in which there are two linearly independent progress variables. New studies by Polster [2] are demonstrating the success of the methods described here.
Probenpotentialmodulation zur Spektroskopie elektronenangeregter Auger-Elektronen mit einem Gegenfeldanalysator
Authors: Brodersen Hans , Institut für Angewandte Physik der Universität Hamburg Andreas , Pickuth Andreas , Legier Werner
Published: February 2015

Electron excited Auger electrons are always superposed with primary electrons rescattered by the sample. A technique for separating the characteristic Auger spectrum from the total energy distribution is described. The method uses a retarding field analyser and modulation of the sample potential instead of the usual retarding grid modulation. Theoretical aspects of this method and illustrating experimental results with samples of amorphous carbon and KCl are discussed. The suppression of the spectrum of the scattered electrons allows recording of Auger spectra with excitation energies near threshold. This low energy excitation minimizes surface destruction of samples, which are sensitive to electron induced dissociation as in the case of alkali halides. The improved signal-background-ratio of the Auger spectra measured with sample potential modulation and the possibility for simultaneous LEED investigations gives a new attractivity to the retarding field analyser.
Electronic Structure and Photophysical Characteristics of Substituted 3-(2-Benzthiazolyl)-Coumarins and Coumarinimines
Authors: Nikolova P. , Tyutyulkova N. , Dryanska V.
Published: February 2015

The spectral properties of a group of 3-(2-benzthiazolyl)-coumarins and coumarinimines, some of them having high fluorescence quantum yield (Qf > 0.7), are described.

The quantum -chemical investigations show that the main chromophore of this group of dyes is the 3 -(2-thiazolyl)-2 H -pyran -2-one fragment

i.e . the coumarin (coumarinimine) and the benzthiazolyl fragments are not separate chromophores.
Bifurcation and Stability Analysis of a One-Dimensional Diffusion-Autocatalytic Reaction System
Authors: De Dier B. , Walraven F. , Janssen R. , Van Rompay P. , Hlavacek V.
Published: February 2015

Results of a numerical analysis of a set of one-dimensional reaction -diffusion equations are presented. The basis of these equations is a model scheme of chemical reactions, involving auto-and cross-catalytic steps (“Brusselator”). The steady state problem is solved numerically, fully exploiting the properties of recently developed continuation codes. Bifurcation diagrams are constructed for zero flux boundary conditions. For a relatively large diffusivity of initial species the Brusselator displays a huge number of dissipative steady state structures. At low system lengths a mechanism of perturbed bifurcation may be percieved. Bifurcations coincide with turning points of asymmetric solution branches. Completely isolated solutions prove to exist as well. For the problem without limited diffusion of the initial species, a careful bifurcation analysis show s the existence of a number of higher order bifurcations. At some of these points asymmetric profiles emanate from other asymmetric structures. Bifurcation points and limit points do not necessarily coincide. Stability analysis shows that relatively few steady states are stable. Especially symmetric solutions are found to be stable.
Internal Cation Mobilities in the Molten Binary Systems KNO3-Sr(NO3)2 and KNO3-Ba(NO3)2
Authors: Yang Chao-cheng , Habasaki Junko , Odawara Osamu , Okada Isao
Published: February 2015

The relative differences in internal cation mobilities for the molten binary systems (K, Sr0.5)NO3 and (K, Ba0.5)NO3 have been measured with the Klemm method in the concentration range up to 34 mol% of the alkaline earth cations. From these and available data on the densities and conductivities, the internal mobilities of these cations, bK, bSr and bBa, have been calculated. In these systems bK and bSr or bBa decrease with decreasing concentration of the K+ ion. bK is well expressed by bK = fK ·bK
*=fK·[A/(V-V0)] exp (-E/RT), where bK
* is the internal mobility of the K+ ion in such melts as (K,Cs)NO3 in which the Coulombic attraction is the dominant factor for the internal mobility of the K+ ion, the constants A, V0, and E being independent of the coion, V is the molar volume of the present mixture and fK the volume fraction of KNO3 in the mixture. At a given mole fraction of K+ ions, the internal mobilities are in the order: Ca<Sr<Ba. This order could be interpreted as the decreasing order of the Coulombic attraction of these cations with the anion.
Phosphoreszenzeigensch aften von Methyl-, Chlor- und Brom-Derivaten des [2.2] Paracyclophans
Authors: Hopf H. , Hermann E.
Published: February 2015

Phosphorescence and fluorescence spectra, quantum yields of phosphorescence and fluorescence as well as phosphorescence lifetimes have been measured of six methyl-, chloro- and bromo-derivatives of [2.2] paracyclophane in ethanol at 77 K. While the chloro-derivatives as well as dibromo-paracyclophane exhibit a normal internal heavy-atom effect behaviour the momobromo-compound shows anomalies. These possibly indicate that in the monobromo-compound an additional pathway of the radiationless deactivation of the lowest triplet state is effective which does not occur with the other compounds.
Über Differenzenverfahren zur numerischen Lösung stark gekoppelter Systeme nichtlinearer Diffusionsgleichungen
Authors: Graf Finck von Finckenstein Karl
Published: February 2015

A class of nonlinear implicit one step difference methods for quasilinear strongly coupled parabolic systems in two space variables is considered. The main part of the paper deals with proving convergence of the discrete approximations for vanishing step sizes. For this purpose, bounds for the inverse difference operators have to be derived previously. This is possible subject to a condition which can be considered as a generalization of the concept “parabolic” to systems. Finally, it is shown that the nonlinear system s arising from the discretizations have one and only one solution for all step sizes being sufficiently small.
On the Stability of Localized Electrostatic Structures
Authors: Schamel H.
Published: February 2015

The eigenvalue problem associated with transverse perturbations of localized one-dimensional electrostatic Vlasov equilibria is analyzed with respect to its spectral and variational properties.
Hamiltonian Formulation and Statistics of an Attracting System of Nonlinear Oscillators
Authors: Tasso H.
Published: February 2015

An attracting system of r nonlinear oscillators of an extended van der Pol type is investigated with respect to Hamiltonian formulation. The case of r = 2 is rather simple, though nontrivial. For r > 2 the tests with Jacobi’s identity and Frechet derivatives are negative if Hamiltonians in the natural variables are looked for. Independently, a Liouville theorem is proved and equilibrium statistics is made possible, which leads to a Gaussian distribution in the natural variables.
An ESR-Study of the Peroxidation of Lecithin Multilayers
Authors: Bartosz Grzegorz , Christ Gabriele , Bosse Harald , Stephan Roland , Gärtner Helmut
Published: February 2015

By means of a set of fatty acid and fatty acid ester spinlabels we found that spontaneous peroxidation of lecithin multilayers increases the rigidity of all regions of the lipid bilayer. However the partition coefficient of TEMPO increased with peroxidation indicating a greater affinity of TEMPO to the modified bilayer.
Determination of the Spin-Rotation and Spin-Spin Interaction Constants of Germane by Microwave Fouriertransform Measurements
Authors: Stahl Wolfgang , Dreizler Helmut
Published: February 2015

We determined the tensorial spin-rotation- (cd) and the spin-spin interaction constant (d) of germane from the hyperfine splittings of Q -branch microwave lines measured by microwave FOURIER transform (MWFT) spectroscopy.
The Doubly Determined Substitution Structure of 1,2-Difluorobenzene
Authors: Stiefvater Otto L.
Published: February 2015

The carbon -fluorine bond length and the distortion of the benzene ring under fluorination have been determined by the isotopic substitution method for 1,2-difluorobenzene. -The experimental work was carried out predominantly by Double Resonance Modulation (DRM) microwave spectroscopy, which allowed the spectra of all 13C-forms to be studied in their natural abundance. The normal and the 4,5-d2 species were used as parent molecules, and the two sets of structure results are found to agree well with each other. With square brackets indicating consistency limits between the two sets of results, the following bond distances (in Å) and angles (in degrees) have been obtained:

C(1/2) - F(1/2) = 1.3494[4] ≮ C(1) C(2) F(2) = 119.16[1]

C(1) - C(2) = 1.3755[3] ≮ C(1) C(2) C(3) = 121.17[2]

C(2/1) -C(3/6) = 1.3786 [3] ≮ C(2) C(3) C(4) = 118.59 [2]

C(3/6) - C(4/5) = 1.4004 [3] ≮ C(3) C(4) C(5) = 120.24 [1]

C(4) - C(5) = 1.3917 [6] ≮ C(2) C(3) H(3) = 119.58 [1]

C(3/6) -H(3/6) = 1.0829 [1] ≮ C(3) C(4) H(4) = 119.55 [1]

C(4/5) - H(4/5) = 1.0813 [4]
The Doubly Determined Substitution Structure of 1,3-Difluorobenzene
Authors: Stiefvater Otto L.
Published: February 2015

The carbon -fluorine bond length and the distortion of the benzene ring under fluorination have been determined by the isotopic substitution method for 1,3-difluorobenzene. -The experimental work was carried out predominantly by Double Resonance Modulation (DRM) microwave spec­ troscopy, which allowed all C13-forms to be studied in their natural abundances. The normal and the 2,4,6,-d3 species were used as the parent molecules, and the resulting two sets of structure parameters are found to agree well with each other. With square brackets indicating consistency limits between the two sets of results deduced by the Kraitchman method, the following bond distances (in Å) and angles (in degrees) have been found:

C(1/3) - F(1/3) = 1.3561 [9] ≮ C(1) C(2) C(3) = 115.74 [6]

C(2) - C(1/3) = 1.3888 [1] ≮ C(2) C(3) C(4) = 123.70 [5]

C(113) - C(6/4) = 1.3745 [7] ≮ C(3) C(4) C(5) = 118.00 [2]

C(4/6) - C(5) = 1.3956 [1] ≮ C(4) C(5) C(6) = 120.86 [1]

C(2) - H(2) = 1.0822[3] ≮ C(1) C(2) H(2) = 122.13 [3]

C(4/6) - H(4/6) = 1.0820 [2] ≮ C(3) C(4) H(4) = 119.92 [1]

≮ C(2) C(1) F(1) = 117.26 [7] ≮ C(4) C(5) H(5) = 119.57 [1]

The bond lenth C(5) - H(5) was assumed as 1.082 ± 0.001 Å.
Neutron Diffraction Study of Amorphous Carbon with a Fast Data Acquisition System
Authors: Annis B. K. , Narten A. H.
Published: February 2015

A fast neutron data acquisition system involving a curved position-sensitive proportional counter is described. The system permits simultaneous measurement of diffraction data over an angular range of 130 degrees at moderate resolution. Data for amorphous carbon are compared with x-ray diffraction data. Structure functions derived from the different methods are in good agreement. Amorphous carbon is a useful standard for the comparison of diffraction data from different laboratories.
Partial Atomic Distribution Functions of Liquid Fe75B25
Authors: Mattern N. , Matz W. , Hermann H.
Published: February 2015

Partial structure factors and atomic distribution functions for liquid Fe75 B25 were determined for the Fe-Fe and Fe-B pairs by means of X-ray and neutron diffraction. The experimental results show a strong chemical short-range order in the melt which is similar to that of amorphous Fe75B25.
Directions of the Electronic Transition Moments in Dioxido-p-terphenyl
Authors: Gryczyński Z. , Kawski A.
Published: February 2015

The directions of the absorption, fluorescence and phosphorescence transition moments of dioxido-p-terphenyl are determined from measurements of the absorption and emission anisotropies as functions of the dichroic ratio in stretched PVA films.
Determination of Spectral Parameters in Microwave Fouriertransform Spectroscopy by Analysis of Time-Domain Signals
Authors: Haekel J. , Mäder H.
Published: February 2015

Some disadvantages of using the Fouriertransform algorithm to obtain rotational spectra from microwave pulse induced transient signals are demonstrated. To overcome the difficulties, a fitting procedure is suggested which is based on the analysis of time-resolved data.
Dimerization of Carboxylic Acids in Solution up to High Pressures and Temperatures. 3. Acetic Acid
Authors: Borschel E. M. , Buback M.
Published: February 2015

Acetic acid in dilute solutions of n-heptane and of CCl4 is studied via IR spectroscopy in the region of the C = O and O - H stretching fundamentals at pressures up to 2250 bar and temperatures up to 150°C. Lambert-Beer’s law is shown to be valid for the C = O modes of the acid monomer and of the hydrogen-bonded cyclic dimer in both solvents, which enables the quantitative measurement of the dimerization equilibrium as a function of pressure and temperature. The pressure dependence of dimerization enthalpy and the temperature dependence of dimerization volume are reported and are compared with direct information on the monomer and cyclic dimer species as derived from their O - H fundamental modes.
Quadrupole Hyperfine Structure in the Rotational Spectrum of Benzonitrile
Authors: Vormann K. , Andresen U. , Heineking N. , Dreizler H.
Published: February 2015

We reinvestigated the quadrupole coupling of benzonitrile by an improved technique of microwave Fourier transform (MWFT) spectroscopy and evaluation method. The error of the coupling constants was reduced by one order of magnitude.
Fractionation of Hydrogen Isotopes in Aqueous Lithium Chloride Solutions
Authors: Kakiuchi Masahisa
Published: February 2015

The D/H ratio of hydrogen gas in equilibrium with water vapor over aqueous lithium chloride solutions was measured at 25 °C, using a hydrophobic platinum catalyst. Experimental details are described. The hydrogen isotope effect between the solution and pure water depends linearly on the LiCl concentration up to ca. 12 m, and at higher concentrations a marked deviation from linearity takes place, as was also observed for the oxygen isotope effect measured by Bopp et al. On the basis of these hydrogen and oxygen isotope effects it is concluded that H2
18O is enriched in the water molecules coordinated to Li+ ions and HD16O is enriched in the free water molecules of the solution. The observed deviation from linearity for concentrations higher than ca. 12m is interpreted in terms of structural changes in the hydration sphere of the Li+ ions.
14N Quadrupole Coupling in the Rotational Spectrum of Ethyl Nitrite
Authors: Keussen Ch. , Andresen U. , Dreizler H.
Published: February 2015

We investigated the 14N quadrupole coupling of three rotational isomers of ethyl nitrite in the ground state by microwave Fourier transform spectroscopy. Centrifugal distortion analyses were necessary to assign the transitions with high J quantum numbers. We found an additional splitting of some c-type transitions of the trans-gauche rotamer presumably arising from tunneling through the barrier separating the two equivalent gauche forms. This assumption could not be confirmed yet.
Deuteron Spin -Lattice Relaxation Times in Undercooled Aqueous Potassium - and Cesium Halide Solutions
Authors: Fink W. , Radkowitsch H. , Lang E. W.
Published: February 2015

Aqueous emulsions of potassium-and cesium halides in cycloalkane mixtures can be undercooled at a pressure of 225 MPa to temperatures around 170K. In these emulsions deuterium spin-lattice relaxation times T1 have been determined as function of salt concentration, temperature and pressure at magnetic fields of 2.4 Tesla and 7.0 Tesla. The frequency and temperature dependence of the relaxation time curves is described quantitatively within a motional model which is consistent with known local structural features in these solutions. Model parameters deduced are compared with those obtained in related studies of the other alkali-halides, and conclusions are drawn regarding the influence of structure and composition on molecular motions.
Fréedericksz Transitions in Crossed Electric and Magnetic Fields
Authors: Barbero G. , Miraldi E. , Oldano C. , Valabrega P. Taverna
Published: February 2015

A homogeneously aligned nematic layer with positive dielectric and diamagnetic anisotropies, placed in crossed electric and magnetic fields orthogonal to the undistorted molecular direction, is considered. Following Deuling's procedure, the possible director field configurations are classified into four types or “phases”, characterized by distortions which are zero, pure twist, splay-bend and mixed type, respectively. It is shown that the transitions between these phases are generally of second order. Simple approximate expressions relating the critical fields and the distortion angles are given for the limiting cases of very small and very large distortions. The validity ranges of the approxima­ tions are found by comparison with the results of a numerical analysis. The experimental critical lines corresponding to three different types of phase transitions, obtained with a ZLI 1738 sample, are compared with theoretical ones. The agreement between theory and experiment is quite satisfactory.
Micro wave Spectra of Furazan I. The Doubly Determined Substitution Structure
Authors: Stiefvater Otto L.
Published: February 2015

Double Resonance Modulation (DRM) microwave spectroscopy has been used to determine the rotational constants of isotopic forms of normal (C2H2N2O2) and perdeuterated furazan (C2D2N2O). From these data the complete substitution structures have been derived by Kraitchman methods and by the computer program GEOM. The latter procedure fails to give correct results due to the decrease of the moment of inertia about the C2v -axis and the simultaneous interchange of inertial axes in the 18O-3,4-d2-form.

The following bondlengths (in Å) and angles (in degrees) are best compatible with the total body of isotopic information:

0 - N = 1.3729 [6] ∢ NON = 111.15 [8]

N -C = 1.3032 [13] ∢ ONC = 105.53 [5]

C -C =1.4211 [9] ∢ NCC = 108.89 [3]

C -H = 1.0763 [5] ∢ CCH = 130.16 [3]

Here, the uncertainties cover small differences between normal and d2-furazan as well as discrepancies resulting from different schemes of structure calculation.
Reversible Energy Transfer and Fluorescence Decay in Solid Solutions
Authors: Twardowski R. , Kuśba J.
Published: February 2015

The article deals with the influence of reversible excitation energy transfer on the fluorescence decay in systems with random distribution of molecules. On the basis of a hopping model, we have obtained an expression for the Laplace transform of the decay function and an expression for the average decay time. The case of dipole-dipole interaction is discussed in detail.
Notizen: On Electromagnetic Spinors and Quantum Theory
Authors: Inskeep Warren H.
Published: February 2015

The Maxwell theory is related to the Dirac theory by two heuristic arguments based on electromagnetic spinors. First, given the condition to have spinors, if the free field Maxwell's equations are satisfied, then the spinors satisfy the Weyl equations. Second, a sufficient condition for electromagnetic spinors directly gives the Weyl equations with the usual substitutions for momentum and energy. It is proposed that the heuristic nature of the first argument is related to the idea of a point having a more general symmetry than a sphere.
Thermionic Electron Emission of Tungsten Bronzes. K0.30WO3 and Rb0.30WO3
Authors: Zocchi F.
Published: February 2015

The work functions and thermionic constants of the hexagonal tungsten bronzes K0.30WO3 (φ = 1.76 eV, A = 3 A/ cm2 K2) and Rb0.30WO3 (φ = 1.88 eV, A = 10 A/cm2 K2) are determined and compared with those of the corresponding alkaline metals and hexagonal Cs0.305WO3.
Polarized Optical Absorption and Emission of Pt (II)Complexes:Single Crystal [Pt(o-phen)(en)]Cl2 · 2H2O
Authors: Schwarz R. , Gliemann G.
Published: February 2015

The influence of temperature (1.9 ≦ T ≦ 295 K) on the polarized optical absorption and emission spectra of single crystal [Pt(o-phen)(en)]Cl2 · 2H2O is reported. Analysis of the spectra shows that the emission at low temperatures originates from the states of three types of traps located energetically by Δῡ ≲ 5 cm-1, 43 cm-1, and 194 cm-1, respectively, below the triplet exciton band.
Further Properties of a Set of Symmetric Maxwellian Equations
Authors: Guéret Pierre
Published: February 2015

A recently proposed set of symmetric maxwellian equations with a quantum-mechanical coupling term between matter and fields is investigated further. Monopole and dipole solutions are described, from which the momentum of a moving charge is calculated. An alternative derivation of the Dirac quantization condition for monopoles is given.
Crystal Structure of Bis(trimethyltin)Selenate Dihydrateand Rotational Tunnelling of the Methyl Groups
Authors: Zhang Da , Prager Michael , Dou Shi-Qi , Weiss Alarich
Published: February 2015

Rotational tunnelling and librations of methyl groups in bis(trimethyltin) selenate dihydrate, [(CH3)3Sn]2SeO4 · 2 H2O, have been studied at low temperature using inelastic neutron scattering (INS) technique. Three tunnel transitions at 1.31 μeV, 3.47 μeV, and 21.0 μeV of equal intensity were recorded. In the energy range of phonons a broad, slightly structured intensity distribution is observed. An attempt is made to identify and assign librational modes. The crystal structure of the title compound was determined by single crystal X-ray diffraction. [(CH3)3Sn]2SeO4 · 2 H2O crystallizes orthorhombic, space group D14
2h-Pbcn with 4 molecules in the unit cell. The lattice constants at room temperature are a = 1142.9(3) pm, b = 1304.6(4) pm, and c = 1084.6(3) pm. According to the molecular symmetry, the two "(CH3)3Sn(H2O)" units in molecule are crystallographically equivalent, but the three methyl groups bound to one Sn-atom are inequivalent. This result coincides well with the observation of three tunnel transitions in INS. A comparison with the related compound, bis(trimethyltin) sulfate dihydrate, is presented. The existence of hydrogen bonding and the role of intermolecular interactions on rotational tunnelling are discussed.
Comment on the Chaotic Behaviour of van der Pol Equations with an External Periodic Excitation
Authors: Steeb W.-H. , Huang Jeun Chyuan , Gou Yih Shun
Published: February 2015

The limit cycle system with an external periodic force d2u/dt2 - a( 1 - u2)du/dt + un = kcos(Ωf) (n = 1, 3, 5,...) can show chaotic behaviour for certain values of a, k and Ω. We study the influence of n on the chaotic behaviour. For n = 1 we select values which result in chaotic motion of the system. Then we investigate the behaviour of the system for n = 3, 5 and 7. Introducing the nonlinearity un(n - 3, 5, 7) gives the surprising result that the chaotic motion ceases to exist.
Hydrogen in Electrodynamics II. Mathematical Means
Authors: Sallhofer Hans
Published: February 2015

After a discussion of the one-component Schrödinger (1926) and the four-component Dirac (1928) represention of hydrogen it is shown that the six-component electrodynamic picture turns out to be considerably simpler and clearer. The computational effort is reduced to a fraction.
Monte Carlo Simulation of Electronic Excitation Migrationand Trappingin Disordered Two-Component Systems. A Comparison with Analytical Theories
Authors: Błonski Sławomir , Bojarski Czesław
Published: February 2015

Monte Carlo simulations of quantum yield and anisotropy of fluorescence in two-component systems have been conducted with various donor and acceptor concentrations and Förster radii ratios RDA
O/RDD
O. The influence of excitation migration and trapping on the fluorescence of the viscous solution has been considered. The results of the simulations have shown that steady-state fluorescence of a two-component system depends on the RDA
O/RDD
O ratio as predicted in LAF theory.
An Improved Estimate of the "Attractive Region" and Modelling of Fluctuation Spectra
Authors: Tasso H.
Published: February 2015

A previous estimate made by the author for the attractive region of a system of van der Pol-like oscillators is now improved. It leads to a richer class of attracting systems whose statistics generates a larger class of fluctuation spectra.