bluuebunny/crossref_metadata_2025_split huggingface dataset:
Einfluß von Substituenten und polaren Lösungsmitteln auf die Deaktivierung des S1Zustandes bei Donator-Akzeptor-substituierten trans-Stilbenen/Influence of Substituents and Polar Solvents on the Deactivation of the First Excited Singlet of Donor-acceptor Substituted Trans-stilbenes
Authors: Gloyna D. , Kawski A. , Gryczyński I. 
Published: February 2015

Abstract
The effect of substituents on the fluorescence quantum yield φf of trans-stilbenes (1) in dimethylformamide, acetonitrile, and n-propanol, as well as in n-heptane, is mainly due to radiationless deactivation. Contrary to n-heptane, the rate kd of radiationless deactivation in the above mentioned polar solvents for compounds 1 of similar structure is not a monotoneous function of the polarity of the first excited singlet state. The maximum of kd corresponds to compounds with medium polarity (1h, 1i). The effect of substituents on the fluorescence rate kf
n in polar and nonpolar solvents is small compared to that on kd. In all solvents kf
n drops with increasing polarity of the first excited singlet state.
Notizen: The Electrical Conductivity of Molten Lead Iodide
Authors: Easteal A. J. , Khoo P. H. 
Published: February 2015

Abstract
The electrical conductivity of molten PbI2 has been determined in the temperature range 798-978 K. The data have been fitted to the equation
χ= -0.8167 + 1.5668 x10-3T + 3.810 x10-7 T2.
The data are compared with previously published data for PbI2.
Notizen: Anthracene and its Argon Complexes, Spectra and Lifetimes
Authors: Hays T. R. , Henke W. , Selzle H. L. 
Published: February 2015

Abstract
Fluorescence excitation spectra and fluorescence lifetimes at specific wavelengths are reported for anthracene and anthracene-argon complexes in a supersonic jet. At low argon pressures, complexes are observed with lifetimes and transition energies which are not dependent on the argon pressure.
At high pressures, the lifetimes reach a limiting value while the wavelength maximum continues to red shift within the pressure range observed. The possible relationship to solvent or matrix effects on a central ion are discussed.
Stabile Radikalanionen von Aromaten: Strahlenchemische Erzeugung in Gegenwart von Natrium-dihydridobis( 2-methoxyethoxy) aluminat
Authors: Getoff Nikola , Haenel Matthias W. , Hildenbrand Knut , Richter Udo-Burckhard , Solar Sonja 
Published: February 2015

Abstract
Arenes are reduced at room temperature to their very long-lived radical anions by exposing the solution of the arene and NaAlH2(OCH2CH2OCH3 )2 (1) in dimethoxyethane (DME) to an ionizing radiation (electrons, gamma- or X-rays) for few minutes:

Thereby 1 is acting as a scavenger for the solvent counter ions which are produced concomitantly to solvated electrons by the radiolysis. The method is very convenient for the ESR and UV-VIS spectroscopy of aromatic radical anions.
Self-Similar Statistics in MHD Turbulence
Authors: Camargo S. J. , Tasso H. 
Published: February 2015

Abstract
The fully developed decaying turbulence of 3-d resistive, viscous, incompressible magnetohydrodynamics is investigated using Elsasser variables and Hopf equation for probability distributions. The method is an extension of a previous work for Navier Stokes equations done by Foias et al. based on a suggestion by Hopf. It uses essentially self-similar properties of the statistics, which "almost" determine the turbulence spectrum up to a mild assumption on an unknown function. This spectrum is the well known Kolmogorov spectrum
Compressibility and Resistive Ballooning Modes
Authors: Correa-Restrepo D. 
Published: February 2015

Abstract
For equilibria stable with respect to ideal ballooning modes it is shown by means of a simple argument that, owing to plasma compressibility, resistive ballooning modes with small growth rates can only exist if they are extended along a field line. In particular, a small region of bad curvature along a field line is not sufficient for the existence of unstable modes
The Millimeter and Submillimeter-Wave Spectrum of Dimethylether
Authors: Neustock W. , Guarnieri A. , Demaison J. , Wlodarczak G. 
Published: February 2015

Abstract
We report the analysis of the rotational spectrum of dimethylether measured between 60 and 400 GHz. Rotational and quartic centrifugal distortion constants are given. Internal rotation splittings are analysed with the I AM method. The value of is compared to the values obtained for similar molecules
Fluorescence, Phosphorescence, and E-Type Delayed Fluorescence of Hexabenzo [bc,ef,hi,kl,no,qr] coronene
Authors: Fetzera John C. , Zander Maximilian 
Published: February 2015

Abstract
The luminescence of hexabenzo [be,ef,hi,kl,no,qr] coronene (I) has been studied in a perhydrocoronene matrix at temperatures from 77 to 353 K. I exhibits phosphorescence and prompt and E-type delayed fluorescence. The phosphorescence transition is symmetry-forbidden. The luminescence behaviour of I is closely related to that of coronene (II)
A Theoretical Study of Monosubstituted Fulvenes
Authors: Jarjis Hayfa M. , Khalil Salim M. 
Published: February 2015

Abstract
MINDO-forces calculations have been done after complete optimization of geometry on X-monosubstituted fulvenes, where X is OH, NH2 , CH3, NO2, CN, F, dimethyl and cyclopropyl. It was found that all the substituents are stabilizing. The electron releasing substituents increase the dipole moment at the exocyclic double bond while the electron withdrawing ones increase the dipole moment at the endocyclic diene. Geometrical parameters, heats of formation, orbital energies and electron densities are reported.
On the Use of Perhydrocoronene as a Matrix in the Luminescence Spectroscopy of Polycyclic Aromatic Hydrocarbons
Authors: Fetzer John C. , Zander Maximilian 
Published: February 2015

Abstract
Higher molecular polycyclic aromatic hydrocarbons (PAH) form supersaturated solid solutions in perhydrocoronene. With coronene as the solute, concentration-dependent P-type delayed fluorescence is observed at 77 K. Even very small amounts of coronene, present as an impurity in the perhydrocoronene matrix, can lead to quenching of the phosphorescence of an added guest PAH by intermolecular triplet-triplet energy transfer and to sensitized coronene phosphorescence when the lowest triplet state of the added guest molecule lies higher in energy than that of coronene. Thermal band broadening of guest molecule phosphorescence has been studied in the temperature range from 77 to 433 K.
Nonlinear Instabilities, Negative Energy Modes and Generalized Cherry Oscillators
Authors: Pfirsch D. 
Published: February 2015

Abstract
In 1925 Cherry [1] discussed two oscillators of positive and negative energy that are nonlinearly coupled in a special way, and presented a class of exact solutions of the nonlinear equations showing explosive instability independent of the strength of the nonlinearity and the initial amplitudes. In this paper Cherry's Hamiltonian is transformed into a form which allows a simple physical interpretation. The new Hamiltonian is generalized to three nonlinearly coupled oscillators; it corresponds to three-wave interaction in a continuum theory, like the Vlasov-Maxwell theory, if there exist linear negative energy waves [2-4, 5, 6], Cherry was able to present a two-parameter solution set for his example which would, however, allow a four-parameter solution set, and, as a first result, an analogous three-parameter solution set for the resonant three-oscillator case is obtained here which, however, would allow a six-parameter solution set. Nonlinear instability is therefore proven so far only for a very small part of the phase space of the oscillators. This paper gives in addition the complete solution for the three-oscillator case and shows that, except for a singular case, all initial conditions, especially those with arbitrarily small amplitudes, lead to explosive behaviour. This is true of the resonant case. The non-resonant oscillators can sometimes also become explosively unstable, but the initial amplitudes must not be infinitesimally small. A few examples are presented for illustration.
Onsager's Relation and Other Results for Relativistic Electrons in Magnetic Fields
Authors: Holas A. , Olszewski S. , Pftrsch D. 
Published: February 2015

Abstract
Onsager's result concerning the quantization of the magnetic flux enclosed by the orbit of an electron moving in a static uniform magnetic field is shown to hold also in the relativistic case, and not to be restricted to the regime considered by Onsager in which the correspondence principle can be applied. The results obtained via the correspondence principle and via expectation values differ, however, in the deails. It is shown also that the eigenenergies and eigenfunctions of Dirac's relativistic equation for an electron in a static non-uniform and arbitrarily strong magnetic field may be obtained directly from the solutions of Schrödinger's non-relativistic equation. In this case the expectation value of an observable depending on coordinates only equals the one calculated directly with the non-relativistic eigenfunctions.
A Laser Limit Cycle - An Analytical Study
Authors: Yao Demin , Großmann Siegfried 
Published: February 2015

Abstract
The limit cycle behaviour of the intensity and of the polarization of a monochromatic two-polarization- mode laser with an intensity coupling asymmetry and a linear phase anisotropy is studied analytically. In a previous paper we found such limit cycle oscillations numerically. Explicit formulae are derived by perturbation methods for the case of small intensity coupling asymmetry and for the case of large pumping, respectively, which describe the dependence on the laser parameters of the limit cycle period as well as of its amplitude.
Motions of Methylammonium Ions in (CH3NH3)2ZnBr4 Crystals Studied by 1H NMR and Thermal Measurements
Authors: Ishida Hiroyuki , Takagi Kentaro , Iwachido Tadashi 
Published: February 2015

Abstract
Measurements of the 1H spin-lattice relaxation time T1, the linewidth parameter T*2
the second moment of 1H NMR absorption, differential thermal analysis, and differential scanning calorimetry were performed on methylammonium tetrabromozincate(II) crystals from 58 to above 500 K. A solid-solid phase transition was located at 456 K. In the room temperature phase, 120° reorientational jumps of CH3 and NH3
+ groups in the cation about its C -N bond axis were detected. In the high-temperature phase, the cations undergo overall reorientation as well as translational self-diffusion. The activation energy for the cationic self-diffusion was evaluated to be 18 kJ mol-1 .
Absorption and Luminescence Studies of Some Highly Fluorescent Derivatives of Vitamin B1; Solvent and pH Effects
Authors: Marciniak B. , Koput J. , Kozubek H. 
Published: February 2015

Abstract
The influence of solvent on the UV-visible absorption and luminescence spectra of some highly fluorescent vitamin B1 derivatives, the products of the reaction of N-methylated vitamin B1 with cytidine (I), adenosine (II) and 2-amino-4-methylpyridine (III) is studied. Spectroscopic manifestations of protonation of I and II are also investigated using a semiempirical INDO/S CI method. Singlet and triplet energy levels of the free ion and several protonated species are calculated, and transition energies and oscillator strengths are compared with the experimental spectra. Calculated charge densities on heteroatoms in the ground and excited singlet and triplet states are correlated with changes of the experimental pKa values with excitation. The results for I and II are compared with those for the trimethylated pyrichrominium ion (III) previously studied
Notizen: Pressure Dependence of the Melting of RbHS04
Authors: Friesel Milan , Baranowski Bogdan , Lunden Arnold 
Published: February 2015

Abstract
The temperature and enthalpy of melting have been studied in the range up to 0.55 GPa by means of differential scanning calorimetry. In the range below a triple point at (498 ± 5) K and (0.27 ±0.02) GPa the results can be expressed by means of linear relations: 7 = 476 + 80 p, and AH = 22.4- 29.8 p, where the corresponding units are K, kJ/mol and GPa. Above the triple point the correlation between pressure and temperature corresponds to Simon's equation, p = 0.27 +1.57 x 10-3 (T-498)1.28, and the enthalpy of melting decreases linearly with the pressure: ΔH = 9.50-10.65 (p-0.28). Comparison is made with a recent study by Sinitsyn et al
Flüssigkristalle mit monosubstituierten alicyclischen und heteroalicyclischen Ringen
Authors: Vill V. , Thiem J. 
Published: February 2015

Abstract
Twenty two liquid crystalline mono-substituted cyclopentanes and cyclohexanes including their oxygen analogues were prepard and studied. Smectic phases with clearing temperatures ≦ 80 °C were observed, and these do not differ considerably between the esters of the more flexible five-membered ring derivatives and those of the conformationally more rigid six-membered rings. In case of the latter, decreasing clearing points are observed with increasing ratios of the axial conformation (static conformational effect). Altogether rather low clearing points are observed, which may be interpreted by a dynamic conformational effect owing to which fast ring inversion causes the compounds to appear in a bulkier shape, and this results in a disadvantageous packing in the mesophase.
Rotational Depolarization of Fluorescence of Prolate Molecules
Authors: Kawski A. , Kojro Z. , Bojarski P. , Lichacz J. 
Published: February 2015

Abstract
The theory of rotational depolarization of fluorescence, taking into account the inertial effect, has been verified experimentally for two angular velocity autocorrelation functions obtained for both the approximate and the exact Langevin equation. To this end, the emission anisotropy was investigated as a function of viscosity for PPO, POPOP, and α-NOPON in liquid n-paraffins (from « = 5 to n = 11) at 304.5 K. For these three luminescent molecules with mean lifetimes of about 1 ns, and the viscosities ranging from 0.22 to 0.9 cP, no essential difference was found between the experiment and the theory for the angular velocity autocorrelation functions employed.
The Bond Sn-Cl in SnIV Complex Salts A2 [(C2H5 )SnCl 5]. A Single Crystal 35Cl NQR Study of Bis(methylammonium)- pentachloroethylstannate, (CH3NH3 )2](C2H5 )SnCl5]
Authors: Storck Peter , Weiden Norbert , Weiss Alarich 
Published: February 2015

Abstract
Zeeman 35Cl NQR spectroscopy has been applied to determine the magnitude and orientation of the EFG tensors at the chlorine sites in a single crystal of(CH3NH3)2[(C2H5)SnCl5] at 293 K. The assignment of the NQR frequencies vi(35Cl), the corresponding quadrupole coupling constants eQΦ(i)
zz h-1 , and the asymmetry parameters ηi(35Cl) to certain Cl(k) atoms is discussed. The most probable assignment is (no. i of vi(35Cl), vi(35Cl)/MHz, eQΦ(i)
zz h-1 / MHz ηi, (35Cl), no. k of assigned Cl(k), d(Sn-Cl(k) )/pm, ∢ (Φ(i)
zz , d(Sn-Cl(k) )) :i = 1,17.032, 34.046,0.056, k= 1, 242.6, 3.1°; i = 2, 12.072, 24.089, 0.117, k = 3, 250.7, 1.9°; i = 3, 11.537, 22.992, 0.146, k = 2, 253.1, 2.8°; i = 4, 10.770, 21.455, 0.154, k = 4, 249.7, 2.9 °; i = 5,9.969,19.842,0.171, k=5,254.9,1.7°. The orientation of the tensor axes Φ(i)
jj , j = x, y, z,i= 1 - 5 , in space is mainly determined by the geometry of the [(C2H5)SnCl5]2⊖ anion. The Φ(i)
zz are nearly parallel to the assigned bond directions Sn-Cl(k) · η (35CI) is low, increasing with decreasing v(35Cl). The reason for the asymmetry seems not to be a π-character in the Sn-Cl bond, but the charge distribution within the anion. The rule that a longer bond corresponds to a lower NQR frequency is valid as a general tendency, but not strict.
NQR Studies of Atomic Arrangements and Chemical Bonding in Glasses
Authors: Lee Donghoon , Gravina S. J. , Bray P. J. 
Published: February 2015

Abstract
A very high sensitivity continuous wave NQR spectrometer was developed to detect pure NQR transitions at low frequencies (down to 200 kHz). A signal-to-noise ratio of more than 100 to 1 has been achieved at about 1.36 MHz for crystalline B 2 0 3 . Two large n B responses have been found in vitreous B 2 0 3 (NMR detected only one site) with linewidths of less than 30 kHz. 27 A1 NQR spectra were obtained for OC-A1203 (Corundum), the mineral andalusite (a form of A1203 • Si0 2), and a glass having the composition of anorthite (CaO • A1203 • 2Si0 2).
NQR in Dipolar and Quadrupolar Glasses
Authors: Blinc R. 
Published: February 2015

Abstract
It is shown that nuclear quadrupole resonance and quadrupole perturbed magnetic resonance represent a powerful technique to determine the local polarization distribution and its second moment, the Edwards-Anderson order parameter, in proton and deuteron glasses. For quadrupolar glasses the local orientational distribution function can be determined from the inhomogeneous NMR or NQR lineshape, thus allowing for a measurement of the quadrupolar Edwards-Anderson order parameter. The comparison of the temperature dependences of the thus obtained order parameters with theoretical predictions then allows for a discrimination between the different possible models of the glassy transition.
35Cl NQR Study of 4,4 , -Dichlorobenzophenone
Authors: Wolfenson A. E. , Pusiol D. J. , Brunetti A. H. 
Published: February 2015

Abstract
Pulsed NQR has been used to get information about the two phase transitions (PT) in 4,4'-di-chlorobenzophenone. The measurements of the NQR spectrum and spin-lattice relaxation suggest that the PT's correspond to a normal-incommensurate and to the lock-in of a commensurate structure at lower temperature. Strong hysteresis has been observed, which could be assigned to memory effects produced by defect migrations.
NQR and NMR Studies of Spin Dynamics in High Tc Superconducting Cuprates
Authors: Warren W. W. , Walstedt R. E. 
Published: February 2015

Abstract
Recent NQR and NMR studies of Cu spin dynamics in metallic YBa2Cu3O6+x are reviewed. The Cu nuclear relaxation rates are shown to be inconsistent with weak correlation (band) theory and the Korringa relation, but the Cu spins retain important characteristics of itinerancy. These include pairing of the Cu d-spins in the superconducting state and strong sensitivity of the Cu spin dynamics to changes in carrier concentration associated with variation of the oxygen content. Samples of reduced oxygen content (Tc = 60 K) are found to contain a high concentration of Cu+ Cu(1) sites associated with "full chain-empty chain" vacancy ordering. These samples also exhibit remarkable precursive suppression of planar Cu(2) nuclear relaxation above Tc .
Cu NQR Studies of the Superconductors YBa2Cu3Ox and YBa2Cu4O8
Authors: Brinkmann D. 
Published: February 2015

Abstract
The paper reviews some copper NQR studies in the superconductors YBa2Cu3Ox and YBa2Cu4O8 performed at the University of Zürich. The following topics are discussed: the temperature and pressure dependence of the NQR frequencies; relation between linewidths and oxygen deficiency; the determination of the electric field gradients (EFG) and Knight shifts at the copper sites; discussion of some calculations of the EFG tensors; measurements of the various relaxation times in all phases. The results obtained in both structures are compared; possible interpretations are discussed.
NQR and Low-Field NMR of 181Ta in the Low-Temperature CDW State of 2 H-TaS2
Authors: Nishihara H. , Hayashi K. , Naito M. , Butz T. , Lerf A. , Saibene S. 
Published: February 2015

Abstract
NQR and low-field NMR spectra of 181 Ta are reported to probe the electronic environment of inequivalent tantalum sites in the low-temperature CDW state of a layered compound 2H-TaS2 . The overall features are found to be consistent with the structure consisting of nine-atom snowflake clusters in a locally commensurate CDW state.
Cu NQR Study on Transverse Relaxation Rate below T c in YBa2Cu3O7
Authors: Tei M. , Takai H. , Mizoguchi K. , Kume K. 
Published: February 2015

Abstract
The transverse relaxation rate T2
-1 was measured in YBa2Cu3O7 from 4.2 to 100 K in zero magnetic field. It showed a sudden drop just below T c down to 1/3 of that above Tc . A cusp-shaped sharp peak of T2
-1 was found at 35 K for Cu(2) (plane) site, but not for Cu(l) (chain) site. Except the peak, all the behavior can be interpreted by the model of Pennington et al. that the origin of T2
-1 at 100 K is mainly the local field fluctuation by the Cu d-electron and secondly the indirect nuclear spin-spin coupling via superexchange interaction between Cu-ions. Below Tc the former is sup-pressed.
Anomalous Temperature Dependence of NQR Frequencies
Authors: Brown R. J. C. 
Published: February 2015

Abstract
The anomalous temperature dependence of NQR frequencies which is often observed in crystals in which there is reorientational motion of ions or molecules is considered. Two theories of the phenomena, the jump rotation theory and the pseudo-spin theory, are described, and their successes and failures are discussed. The importance of considering other properties such as pressure dependence of NQR, heat capacity, and elastic constants is emphasized, and it is shown that neither theory is entirely satisfactory at present.
A Study of Complex Anionic Motions in (Me2NH2)2ZnCl4 Crystals by Means of Chlorine Nuclear Quadrupole Resonance Techniques
Authors: Yamamoto Hiroshi , Ishikawa Atsushi , Asaji Tetsuo , Nakamura Daiyu 
Published: February 2015

Abstract
Three 35Cl NQR frequencies were observed for (Me2NH2)2ZnCl4 at room temperature, indicating the existence of three crystallographically nonequivalent chlorines in the crystal. With decreasing temperature, the frequency of the lines increased almost linearly and disappeared below ca. 220 K near the reported phase transition temperature (ca. 215 K) detected on cooling. The three NQR lines faded out above room temperature because of the occurrence of rapid anionic reorientational motions disclosed from measurements of the 35Cl NQR spin-lattice relaxation time.
Proton Spin Relaxation of a Liquid Crystal with a Glassy Cholesteric State
Authors: Pusiol D. , Noack F. , Aguilera C. 
Published: February 2015

Abstract
Field-cycling and standard pulsed NMR techniques have been used to study the frequency dependence of the longitudinal proton spin relaxation time T x in the crystalline estradiol compound (+)3,1,7-ß-bis-(4n-butoxybenzoyloxy)-estra-1,3,5-(10)-trien or BET, which is a mesogenic material with a chiral molecular structure. From the measured Larmor frequency and temperature depen-dences we conclude that, at low NMR frequencies in the cholesteric phase, T1 reflects in addition to the relaxation process familiar from nematic liquid crystals (director fluctuation modes) another slow mechanism theoretically predicted for cholesteric systems, namely diffusion induced rotational molecular reorientation. These relaxation processes are not or much less effective in the crystalline and glassy state, where they are frozen. Also the high NMR frequency relaxation dispersion strongly differs between the cholesteric mesophase and the not liquid crystalline samples. This is interpreted by a change from essentially translational self-diffusion to rotational diffusion controlled proton relaxation.