bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Fractal-Like Crystal Growth
Authors: Felinger Attila , Liszi Jänos
Published: February 2015

Non-equilibrium crystallization was simulated on a two dimensional square lattice. Several clusters were grown simultaneously by using the model of diffusion limited aggregation. The growing process was reversible, i.e. dissolution of particles from the boundary of any cluster was made possible. The rate of growth and dissolution was determined by a stochastic method. The simulation resulted in an aggregate pattern having a few large and several small clusters. The fractal dimensions of the large clusters were found in the range of D = 1.62-1.72.
Multiaxial Reorientationsof ND+
4 Ions Studied by 2H-NMR Spectroscopy
Authors: Lalowicz Z. T. , Sagnowski S. F.
Published: February 2015

The density matrix formalism is used to simulate motional averaging in the 2H-NMR spectra of reorienting ND+
4 ions. The development of the spectra under increasing jump frequency about a single C3 or C2 axis is followed. Next we assume a hierarchy of axes in terms of activation energies sufficient to reach extreme narrowing conditions for some axes before activating jumps about a next one. Primary reorientations about the fastest C3 or C2 symmetry axes define the shape of spectra, the width of which is then stepwise reduced by fast reorientations about the subsequent axes in a postulated sequence of statistically uncorrelated jumps.
Hydrogen in Electrodynamics. VII The Pauli Principle
Authors: Sallhofer Hans
Published: February 2015

After a discussion of the one-component Schrödinger (1926) and the four-component Dirac (1928) representation 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.
A Molecular Dynamics Study of Ionic Hydration Near a Platinum Surface
Authors: Seitz-Beywl J. , Poxleitner M. , Heinzinger K.
Published: February 2015

Two Molecular Dynamics simulations have been performed where a Pt(100) surface is covered with three layers of water molecules and a lithium or an iodide ion is placed additionally in the boundary layer. The flexible BJH model of water is employed in the simulations and the ion-water, platinum-water and platinum-ion potentials are derived from molecular orbital calculations. The simulations extended over 7.5 ps at an average temperature of 298 K. The effect of the Pt(100) surface on the ionic hydration is demonstrated by the comparison of the radial distribution functions, the orientation of the water molecules and their geometrical arrangement in the first hydration shells of the ions in the boundary layer with those in a 2.2 molal bulk Lil solution.
MINDO-Forces Study of α-Substituted Cyclopropyl and Isopropyl Radicals
Authors: Khalil Salim M. , Jarjis Hayfa M.
Published: February 2015

The structures of α-X-cyclopropyl and α-X-isopropyl radicals (X = H, O-, OH, NH2, CH3, NO2, CHO, CN, F and CF3) are reported using MINDO-Forces MO method. In both radicals the planar structure is prefered over the pyramidal. All the substituents are stabilizing; the O- group is the most stabilizing substituent, while F group has little effect. O- , OH, F substituents are electron releasing groups on cyclopropyl ring, while NO2, CHO and CF3 are electron widthdrawing. For isopropanes and x-X-isopropyl radicals, O-, OH, NH2 and F act as electron releasing, while NO, and CF3 act as electron withdrawing. The strain energies of the cyclopropyl radicals (43.8-23.7 kcal/mol) are compared with those of similarly substituted cyclopropanes. Dipole moments and spin densities are reported.
Local Structure of the Amorphous Ni25Zr75-Alloy by Using the Isotope-Substitution Neutron Diffraction Method
Authors: Kuschke W.-M. , Lamparter P. , Steeb S.
Published: February 2015

Using neutron diffraction as well as the method of isotopic substitution the partial Bhatia-Thornton as well as the partial Faber-Ziman structure factors of amorphous Ni25Zr75 were determined. A compound forming tendency was found. The atomic distances, partial coordination numbers, and the chemical short range order parameter are evaluated.
Oscillating and Inflating Universe in SO(3)-Gravitation Theory
Authors: Mattes M. , Sorg M.
Published: February 2015

The predictions of SO (3) Gravitation Theory are studied for a homogeneous, isotropic universe. Various types of oscillations are obtained for the pre-inflationary phase, where the geometry experiences violent fluctuations. These are ultimately terminating at either re-collaps or regular inflation.
14N Nuclear Quadrupole Hyperfine Structure in the Rotational Spectrum of Thionyl Aniline
Authors: Heineking N. , Grabow J.-U. , Vormann K. , Stahl W.
Published: February 2015

Nuclear quadrupole hyperfine structures have been resolved in the rotational spectrum of thionyl aniline, C6H5NSO, using pulsed molecular beam microwave Fourier transform spectroscopy. High precision nuclear quadrupole coupling constants, rotational and quartic centrifugal distortion constants have been determined from the analysis of 12 low-J transitions. Coupling constants are χaa = + 1.5730(14) MHz and (χbb - χcc)= -5.6499(13) MHz. rotational constants are A-4026.72i5(4) MHz, B = 860.64732(8) MHz, and C = 709.52027(7) MHz, and centrifugal distortion constants are ΔJ - 36.6(5) Hz, ΔJK= -107.5(20) Hz, ΔK = 703(68) Hz, δJ = 8.1(5) Hz, and δK=111(19) Hz (representation I' used).
Structure and Reactions of Radicals Derived from Cyclopentane, Cyclopentenes, and Cyclohexenes in Low-Temperature Matrices. An ESR Study
Authors: Kubozono Yoshihiro , Okada Makoto , Aoyagi Makoto , Yahiro Shuichi , Gondo Yasuhiko , Nakamura Hiroshi , Matsuo Taku
Published: February 2015

The radical species derived from cyclopentane, cyclopentenes and cyclohexenes by 60Co γ-ray irradiation at 77 K in halocarbon matrices have been studied by ESR spectroscopy. The electronic and geometrical structures of the radical species are discussed on the basis of the experimental hyperfine coupling constants and semiempirical MO calculations. Exposure of the tetramethylsilane frozen solution containing cyclopentene to 60Co γ-rays produced specifically 3-cyclopenten-l-yl.
On the Scaling of Type-1 Intermittency in a Semiconductor Experiment
Authors: Richter R. , Rau U. , Kittel A. , Heinz G. , Peinke J. , Parisi J. , Huebener R. P.
Published: February 2015

Spontaneous oscillations developing during low-temperature impact ionization breakdown in extrinsic germanium are looked at with respect to characteristic features of type-I intermittency
Deactivation of the S,-State of w-Substituted 4-Dimethylamino-trans-Styrenes in Alkane Solutions
Authors: Kawski A. , Gryczyński I. , Nowaczyk K. , Bojarski P. , Lichacz J.
Published: February 2015

Deactivation of three co-substituted acceptors in 4-dimethylamino-trans-styrenes (P(S)Ph2 (la), P(0)Ph2 (2a) and SO2CH3 (3a)), dissolved in «-paraffins (from n = 5 to n = 16) at 293 K, was investigated. Trans-cis isomerization and intersystem crossing are the main processes responsible for radiationless deactivation of the S1 excited state. High fluorescence anisotropy, r, observed in low-viscous «-paraffins, is due to strong fluorescence quenching resulting in the considerable shortening of the lifetime τ of these molecules. The fluorescence depolarization which occurs when lowering the viscosity, η, of the solution is caused by Brownian rotations and conformational changes due to fast adiabatic twisting of the planar trans-S1 form around the double bond, leading to the formation of the perp.-S1 structure with perpendicularly oriented parts of the molecule, and to the concomitant change in the transition moment direction. Linear dependence of τ2{r0/r - 1) on η - τ in the whole viscosity range was only observed for molecule 3a
On Lower Bounds for the Free Energy of the Hubbard Model
Authors: Steeb W.-H. , Villet C. M.
Published: February 2015

Two lower bounds for the free energy of the Hubbard model are compared
On the Electric Multipole Moments of Carbon Monoxide
Authors: Maroulis George
Published: February 2015

The electric dipole, quadrupole, octopole and hexadecapole moment of carbon monoxide has been obtained from finite-field SCF and Moeller-Plesset perturbation theory calculations. The resulting values for the octopole and hexadecapole moments of CO(X1 Σ+ ) are 3.59 eao
3 and - 9.01 eao
4 respectively
Raman Spectroscopic and X-ray Diffraction Studies on Concentrated Aqueous Zinc (II) Bromide Solution at High Temperatures
Authors: Takamuku Toshiyuki , Ihara Mikito , Yamaguchi Toshio , Wakita Hisanobu
Published: February 2015

Raman and X-ray scattering experiments have been performed on an aqueous zinc (II) bromide solution with molar ratio [ H2 0] / [ ZnBr2 ] =10 at 25 to 140 °C. The intensity of the totally symmetric Zn - Br stretching vibration (ν1) for the dibromozinc(II) complex increased with increasing temperature while that for the tetrabromo complex decreased. A broad band assigned to the symmetric Zn - O stretching vibration ( ν1 ) for the aqua zinc (II) ion decreased in intensity with increasing temperature. The X-ray diffraction data revealed that the average number of the Zn - Br interactions within the zinc (II) bromo complexes does not change with temperature, whereas the number of Br ··· Br nonbonding interactions within the complexes decreases from 1.8 at 25 °C to 1.5 at 100 °C. From both Raman and X-ray data it is concluded that with increasing temperature the dibromo species is favored, whereas the tetrabromo and aqua zinc(II) species are unstable in the solution. The analysis of the X-ray diffraction data has shown that the mean Zn - Br bond length within the zinc (II) bromo complexes shortens gradually with increasing temperature, accompanied with an increase in the interligand Br ···Br distance. This finding suggests that the Br - Zn - Br bond angle increases with decreasing Zn - Br distance for the lower zinc(II) bromo complexes. The equilibrium shift of the zinc (II) bromo complexes with temperature is discussed on the basis of ion-ion, ion-water, and water-water interactions
High-Resolution Vibrational Spectra of Furazan II. The B1 Fundamental ν 11 at ~ 1175 cm–1 from Fourier-Transform Infrared Spectroscopy
Authors: Stiefvater Otto L.
Published: February 2015

The high-resolution FT-IR spectrum of the A-type fundamental ν11 of furazan ( C2H2N20) has been recorded and analysed against the background of rotational information from DRM microwave spectroscopy to yield the band origin as ν11
0= 1175.3377 + 0.0001 cm-1 . The combined use of microwave (MW) and FT-IR data gives this band origin with a statistical uncertainty of σ= 10-6cm-1 and leads to a refinement of the rotational constants of the state ν11 = 1 over those derivable from either MW or FT-IR data alone
The Rotational Zeeman Effect in Acetone, its g-Tensor, its Magnetic Susceptibility Anisotropics and its Molecular Electric Quadrupole Moment Tensor; A High Resolution Microwave Fourier Transform Study
Authors: Oldag Frank , Sutter Dieter H.
Published: February 2015

Acetone is a molecule with an intermediate barrier for methyl- top internal rotation, and only molecules in the A1A1 - state of the tunneling motion exhibit a rigid rotor spectrum. For this state we report the results of a rotational Zeeman effect study of acetone in exterior fields up to 20 kGauss (2 Tesla). From an analysis of the observed Zeeman splittings within the asymmetric top approximation the nonzero elements of the g-tensor and the magnetic susceptibility anisotropies were obtained as follows: gaa= -0.04379 (8), gbb = - 0.06611 (5), gcc=-O.O1481 (7), 2ξaa -ξbb - ξcc = - 9.53 (21) 10-6 erg G -2 mole-1 and 2 ξbb - ξcc - ξaa = 25.57 (18) 10-6 erg G -2 mole-1 . The nonzero elements of the molecular electric quadrupole moment tensor were derived as Qaa- 2-77 (13) DÅ, Qbb= -4.59 (10) DÅ and Qcc= 1.82 (15) DÅ. Zeeman spectra were also recorded for seveal low-J transitions of molecules in the EE-state of methyl top tunneling (one top tunneling), and so far the same splittings have been found as for the A1 A1-species
Onset of Thermosolutal Convection in a Liquid Layer Having Deformable Free Surface – I. Stationary Convection
Authors: Dandapat B. S. , Kumar B. P.
Published: February 2015

The effect of surface deformation on the onset of thermosolutal convection in a horizontal thin layer heated from below and salted from above is examined, using linear stability theory. It is found that two critical Crispation numbers Cr1 and Cr2 exist. For Cr ≦ Cr1 the instability mechanism remains unefTected by the deformation of the free surface, whereas for Cr1 < Cr < Cr2 the critical Marangoni number (Mc) decreases, showing instability due to deformation. If Cr = Cr2, Mc is obtained for two values of the wave number. When Cr > Cr2 , Mc decreases as the wave number tends to zero. Further, the effect of the Marangoni number, Biot number, Bond number etc. on the stability characteristics of the problem is discussed.
Collisional Isotropisation of a Strongly Magnetized Anisotropic Plasma within the Weak Interaction Approximation
Authors: Schamel H. , Hübner G.
Published: February 2015

The equipartition frequency ν of an anisotropic plasma is calculated numerically and analytically within the Landau approach for strong magnetic fields and several new integral expressions for ν are presented. In the ultra strong magnetic field case, when rc≪b, where rc is the Larmor radius and b the classical distance of closest approach, ν is shown to be dependent on how the Coulomb force is cut off at short distances. None of the obtained expressions, however, coincides with experiment, in contrast to the strong interaction theory of O'Neil and Hjorth. For weaker, but still strong magnetic fields ( rc >b) the ambiguity disappears and the weak interaction result describes well the experiment. It is, hence, the transition region rc ≈ b , where the transition from strong to weak interaction takes place
Large Volume NMR Spectroscopy with a Whole Body Imager
Authors: Lutz O. , Pfeffer M.
Published: February 2015

A whole body NMR imager (1.5 T) has been operated with large samples and a home built coil to study NMR signals of heteronuclei at very low concentrations. Typical examples of 27Al, 51V, and 81Br are given, signals of 1 µmolal aqueous solutions of e.g. NaVO3 can be detected. 129Xe was observed in xenon gas at atmospheric pressure with one scan. A 129Xe gaseous state NMR image is presented in a xenon containing sample. Also some typical measurements of longitudinal relaxation times of 27Al, 51V, and 129Xe are given
Fluoreszenz-Spektroskopie an dünnen im UHV aufgedampften Coronen-Schichten
Authors: Port H. , Wolf H.C.
Published: February 2015

Fluorescence Spectroscopy on UHV-Deposited Thin Films of Coronene

Thin films of coronene, UHV-deposited on different inorganic substrates (Si(111), Si(100), Si/Si02, graphite(0001) and MoS2(0001)) have been investigated via laser induced fluorescence and fluorescence excitation spectra at various coronene coverages (from submonolayers to 1000 Å) and temperatures (4.2 K - 300 K). Independent of the substrate the films reveal a characteristic absorption which is red-shifted with respect to that of the coronene crystal and is attributed to a new film-specific structural modification (in accord with X-ray data). At film thicknesses d > 50 Å this absorption is increasingly superimposed by crystal-type absorption. The fluorescence spectra at low coverages and low temperatures strongly depend on the substrate. On Si/Si02, graphite and MoS2 the fluorescence is similar to that of the coronene crystal. Thin films on Si(100) and Si(111), on the other hand, show monomer-like narrowband fluorescence originating, presumably, in substrate-induced trap states
Dielectric Relaxation of 2-Amino-l-butanol
Authors: Witt U. , Stockhausen M. , Jadżyn J. , Kędziora P.
Published: February 2015

The dielectric relaxation spectrum of the title substance in mixtures with 1,4-dioxane or benzene (pure liquid to moderate mixture ratios) is measured between 5 MHz and 36 GHz at 20°C. The static permittivity is determined over the whole mixture range. The results are discussed in particular with respect to the possibility that different types of hydrogen bonded aggregations may contribute to the main relaxation
The Rotational Spectrum of the Fluorobenzene-Argon Van der Waals Complex
Authors: Stahl W. , Grabow J.-U.
Published: February 2015

The rotational spectrum of the fluorobenzene-argon complex has been studied in the microwave region between 7 and 18 GHz using a pulsed molecular beam microwave Fourier transform spectrometer. The rotational constants were found to be A = 1811.81369(11) MHz, B= 1105.12965(15) MHz, C = 901.84281(5) MHz, the centrifugal distortion constants are ΔJ = 2.6886(17) kHz, ΔJK = 8.3761 (52) kHz ΔJK= -8.278(5) kHz, ρJ, =0.65993(72) kHz, and ρK = 6.013(11) kHz. The argon atom is placed 3.55 Å above the ring plane
Testing the Reverse Monte Carlo Method Using Scattering Data from Amorphous Ni2Zr
Authors: Bionducci M. , Buffa F. , Licheri G. , Navarra G.
Published: February 2015

The reverse Monte Carlo simulation has been tested by modelling the partial distribution functions of amorphous Ni2Zr. Three runs of simulation involving experimental data from isotopic substitutions neutron scattering and X-ray anomalous scattering are presented
Molecular Motions in Solid [Sb(CH3)4]PF6. A Combined 11H,9F Nuclear Magnetic Resonance and Quasielastic Neutron Scattering Study
Authors: Burbach Günter , Weiden Norbert , Weiss Alarich
Published: February 2015

The molecular dynamics of tetramethylstibonium hexafluorophosphate, [Sb(CH3)4]PF6, is investigated over a broad temperature range. NMR spin lattice relaxation times T1 and the NMR second moments of the 1H and 19F nuclei were determined in the range 8.6 ≦ T/K ≦ 332.3 for polycrystalline [Sb(CH3)4]PF6. The complex cation undergoes isotropic tumbling for T > 260 K and thermally activated methyl group rotation in the temperature range T < 196 K. The activation energies for the transition from methyl group rotation to cation reorientation, as derived from NMR wideline (18.1 kJ/mol) and relaxation (22.7 kJ/mol) measurements, match. At very low temperatures pseudo classical line narrowing is observed, indicating tunneling motions of the methyl groups. The existence of two crystallographically inequivalent methyl groups is found by X-ray structure analysis at room temperature. The space group is P63mc, Z = 2; a = 738.6 pm, c = 1089.3 pm. It is confirmed by two steps in the temperature dependence of the signal intensity of the quasielastic line in neutron fixed window measurements in the temperature range 2 < T/K <148. The low temperature spin lattice relaxation times can be explained qualitatively by contributions of two crystallographically inequivalent methyl groups. Apparent activation energies for the two crystallographically different methyl groups are estimated. The complex anion undergoes isotropic tumbling in the temperature range 95 < T/K < 330. Above 330 K additionally translational motion is activated. Below 95 K the rotational motion of PF-
6 is freezing in via an uniaxial state in range 40 < T/K <80. Activation energies for both isotropical tumbling (10.5 kJ/mol) and uniaxial rotation (5.8 kJ/mol) have been derived from 19F NMR spin lattice relaxation
Application of the Pseudo-Spin Model to the Lowest-Temperature Phase Transition of the Mixed Crystal (NH4)2(1-x)K2xPb[Cu(NO2)6]
Authors: Windsch Wolfgang , Braeter Horst , Gonzalo Julio A.
Published: February 2015

Mizuno et al. developed a jumping model to explain the nonlinear decrease of the phase transition temperature in the mixed crystals (NH4)2(1-x)K2xPb[Cu(NO2)6] with 0 ≦ x ≦ 1. Their implications and results are compared with model parameters and with the results of calculation within the Ising model with transverse field. It comes out that the assumption of a temperature independent transient time in the jumping model corresponds to the admission of tunneling in the Ising model.
Determination of a High Potential Barrier Hindering Internal Rotation in 2-Methylcyclopentanone and α-Methyl-γ-Butyrolactone by Microwave Fourier Transform Spectroscopy
Authors: Alonso J. L. , Heineking N. , Dreizler H. , Heineking N. , Dreizler H.
Published: February 2015

The microwave spectra of α-methyl-γ-butyrolactone and 2-methylcyclopentanone have been reinvestigated using microwave Fourier transform spectroscopy. A-E splittings due to internal rotation of the methyl group have been observed in the ground and several vibrationally excited states for both molecules. From an internal-axis-method analysis of these splittings, values of the methyl group internal rotation barrier of 2.61 kcal mol-1 for α-methyl-γ-butyrolactone and 2.41 kcal mol-1 for 2-methylcyclopentanone have been obtained.
A Theoretical Study of Monosubstituted Cyclopropenyl System
Authors: Yahya Noha M. , Khalil Salim M.
Published: February 2015

MONDO-Forces calculations have been performed, with complete optimization of geometry on X-cyclopropenyl system (cations, radicals and anions), where X is H, O-, OH, CH3 , CN, NO2 , F and CF3 . All substituents prefer planar structure when substituted on both cations and radicals, while they prefer pyramidal structure in the case of anions except CF3 . The substituents O-, OH and F act as electron releasing, while CHO, NO2 and CF3 act as electron withdrawing when substituted on cyclopropenyl system. CH3 and CN show amphielectronic behaviour. They act as electron releasing on the cations and withdrawing on both radicals and anions depending on electron demand. In the case of cations and radicals, all substituents were found to increase the vicinal bonds and decrease the distal bonds and bond angles to which the substituent is attached. For anions the substitutents show no such regularity because the substituents are out of the three-membered ring plane. All substituents increase the stability of the cyclopropenyl system except CF3 in the case of the cation.
Factor Analysis of Long Range Substituent Effects on C-13 NMR Chemical Shifts and Target Factor Testing of Different Types of Substituent Parameters
Authors: Fadhil Ghazwan F.
Published: February 2015

A factor analysis technique has been used to analyse 186 long range C-13 substituent chemical shift (scs) of 90 compounds of the general formula X - G - Y ; X represents the set of substituents, G is a hydrocarbon skeleton, in some cases unsaturated (phenylene) and in other cases saturated. Y consists of a variety of groups which contain the probe site. The data were taken from the literature. Although they were measured in different laboratories, the solvent was CDCl3 in every case. From the value of the factor indicator function (IND) it was concluded that two factors were significant. The validity of several empirical and theoretical substituent parameters has been investigated by Target testing. Models were constructed for the substituent effect. Results from Target factor testing, model designing and linear regression analysis have shown that Reynolds’ σO
R and σF are the best substituent parameters in reproducing the C-13 substituent chemical shift.
Internal Cation Mobilities in Molten (Li, Ag)NO3 and (K,Ag)NO3 Remeasured by the Klemm Method
Authors: Okada Isao , Ichioka Kazunori
Published: February 2015

Internal mobility ratios bLi/bAg and bK/bAg in molten (Li,Ag)NO3 and (K,Ag)NO3 have been measured by Klemm’s countercurrent electromigration method. From these and available data on the densities and conductivities the internal mobilities have been calculated. The present experiments yielded more accurate data than previous ones using other methods. Over the investigated range of concentration and temperature, bAg is greater than bu or bK. The results are discussed together with earlier ones obtained for (Na, Ag)NO3 .
The Inertial Effect in Rotational Fluorescence Depolarization
Authors: Kawski A. , Bojarski P. , Kubicki A.
Published: February 2015

The influence of the moment of inertia on the rotational fluorescence depolarization is discussed. Based on experimental results obtained for five luminescent compounds: 2,5-diphenyloxazole (PPO), 2,2'-p-phenylene-bis(5-phenyloxazole) (POPOP), p-bis[2-(5-α-naphthyloxazolyl)]-benzene (α-NOPON), 4-dimethylamino-ω-methylsulphonyl-trans-styrene (3a) in n-parafines at low viscosity (from 0.22 x 10-3 Pa • s to 0.993 x 10-3 Pa • s) and diphenylenestilbene (DPS) in different solvents, a semi-empirical equation is proposed, yielding moments of inertia that are only two to five times higher than those estimated from the molecular geometry
Temperature Dependence of N2-Relaxation of Rotational Lines of Propionitrile
Authors: Nicolaisen H.-W. , Mäder H. , Rohart F.
Published: February 2015

The temperature dependence of the rotational relaxation of propionitrile, CH3CH2C15N, has been investigated by means of microwave transient emission signals. From analysis of the pressure dependence of the coherence decay rates for the rotational lines (J, K-, K+) = (2, 0, 2)-(3, 0, 3), (2,1, 2)-(3, 1, 3), and (2, 2, l)-(3, 2, 2) pressure broadening parameters have been derived for mixtures with nitrogen in the 210-300 K range and for the pure gas at ambient temperatures
NQR and NMR in High Tc Superconductors
Authors: Asayama K. , Kitaoka Y. , Zheng G.-q.
Published: February 2015

Recent NQR and NMR experiments on La2-xSrxCuO4 , YBa2Cu3O7 , Tl2Ba2CuO6+y , and other compounds are reviewed. The antiferromagnetic spin fluctuations decrease in the order of La, Y, T1 compounds. In the normal state the T-dependence of (T1T)-1 is considered to follow the Curie- Weiss law at high temperature and the (Ti 7") = const law at low temperature. The T dependence of 1/T1 below Tc suggests strongly d-wave pairing. Correlations of the NQR frequency of 63Cu and 17O with the antiferromagnetic spin fluctuations and the superconducting transition temperature are discussed.
NQR Studies of the Structure of Glasses and Crystalline Compounds
Authors: Bray P. J. , Lee DongHoon , Mao De Gen , Petersen G. L. , Feller S. A. , Bain D. L. , Feil D. A. , Pandikuthira Ponnappa , Nijhawan Sumit
Published: February 2015

Pure nuclear quadrupole resonance (NQR) spectroscopy at low frequencies (down to 275 kHz) has been used to investigate a number of borate, aluminate, and vanadate crystalline compounds and borate glasses. The values of the quadrupole coupling constants (Qcc) and asymmetry parameters (η) are obtained with error limits that are one or two orders of magnitude less than those for values obtained from NMR spectra. New sites, not resolved in NMR spectra, have been detected for boron in borate glasses.
14N Quadrupole Interactions in Nitrogen-Containing Ceramics. Effects on 29Si NMR Line Shapes and Structural Implications
Authors: Olivieri Alejandro
Published: February 2015

Simulations of solid-state 29Si NMR spectra in nitrogen-containing silicon ceramics and glasses are described. The range of SiNxO4-x tetrahedra is covered, with emphasis on the experimental conditions needed to observe the effect of the incompletely averaged 29Si, 14N dipolar coupling. A simple equation is discussed concerning its use in the interpretation of these 29Si spectra, including the computation of 14N quadrupole coupling constants with its absolute sign.
Electric Field Gradient in Aluminium due to Vacancy and Muon
Authors: Ponnambalam M. J.
Published: February 2015

The electric field gradients (EFG) in aluminium due to a monovacancy and the interstitial muon are evaluated. The valence effect EFG qv is calculated using perturbed electron density δn(r)values obtained from density functional theory in an analytic expression which is valid at all distances from the impurity. The size effect EFG qs is evaluated using a new oscillatory form for the near neighbour (nn) displacements. The numerical values of qs are computed using fractional nn displacements available in the literature. For the total EFG good agreement with experiment is obtained without the use of any parameter.
14N NQR in 1,10-Phenanthroline and Dicyano bis(1,10-phenanthroline)iron(III)*
Authors: Murgich Juan , Aray Yosslen , Ospina Rico Edgar , Bonalde Ismardo
Published: February 2015

14N NQR spectra of 1,10-phenanthroline and of dicyano bis(1,10-phenanthroline)iron(lll) were obtained at room temperature. An analysis based on the shifts of the NQR frequencies and in the topology of the charge distribution in a model (pyridine) showed that the complex formation produces a strong decrease in the N valence shell nonbonded maximum and an increase in the bonded density along each of the N - H bond directions. The NQR spectrum showed that the complex formation produces only small changes in the charge distribution of the cyanide groups.
81Br and 127 I NQR Studies of (CH3NH3)2HgBr4 and (CH3NH3)2HgI4
Authors: Terao Hiromitsu , Okuda Tsutomu , Minami Aya , Matsumoto Takashi , Takeda Yoshio
Published: February 2015

The 81Br and 127I NQR frequencies in (CH3NH3 ) 2HgBr4 and (CH3NH3 ) 2HgI4 , respectively, have been recorded from above 77 K to around room temperature. The resonance lines exist in a wide range of frequencies. An unusual temperature dependence of the resonance frequencies has been observed. Small 1H - 2D isotope effects have been observed between (CH3ND3 )2HgBr4 and (CH3NH3 ) 2HgBr4 . Both negative and positive frequency differences between the deuterated and the nondeuterated compound have been observed at 77 K. The relatively large asymmetry parameters in the iodine compound decrease with increasing temperature, indicating the existence of H-bonds. The present results are interpreted qualitatively by considering the effects of H-bonding, N - H • • • X, between the halogen atoms and the CH3NH3 ions which may undergo large molecular motions. It is suggested that not only frequency-lowering but also frequency-rising effects may be produced, depending on the direction of the H-bond, i.e., the angle between the Hg -X bond and the X • • • H bond.
7Li-Solid-State-NMR of [Li(N,N,N',N'-Tetramethylethylenediamine)] CLO4 and [Li (N,N,N', N'-Tetramethylethylenediamine)2] Al(CH3)4
Authors: Pietraß Tanja , Burkert Paul K. , Karsch Hans H.
Published: February 2015

The temperature dependent 7Li-solid-state-NMR spectra of the two compounds [Li(N,N,N',N'- tetramethylethylenediamine)]ClO4 and [Li(N,N,N\N tetramethylethylenediamine)2]Al(CH3)4 are presented. Both compounds were investigated in the temperature range 160 K ≦ T ≦ 360 K. Above room temperature, the spectra for the tetramethylaluminate show the typical line shape for a first-order quadrupolar-disturbed central transition with an axially symmetric asymmetry parameter and a slightly positive temperature dependence of the quadrupole coupling constant. The mean temperature coefficient ά = + 9 • 10-4 K -1 . The quadrupole coupling constant is in the range of 36-39 kHz. In the Temperature range 240 K ≦ T ≦ 275 K the quadrupolar splitting cannot be resolved. Below 240 K the quadrupole coupling constant is about 100 kHz. Contrarily, in the Perchlorate the quadrupole coupling constant is 75 kHz and is temperature independent. With increasing temperature the satellites lower in intensity and the central transition undergoes motional narrowing
63,65Cu and 79 81Br NQR Studies of Thione Complexes of Cu(I) Halides
Authors: Ramaprabhu Sundara , Lücken Edwin A. C.
Published: February 2015

63, 65Cu NQR frequencies, together with their temperature dependence, are reported for several complexes formed between cuprous chloride or bromide and heterocyclic thiones. For bromides the 79,81Br resonances have also been detected. These results indicate that, with one exception, the copper atom is tricoordinated by two sulphur atoms and one halogen. Several of these complexes show phase changes in the range 77-300 K.
Bromine-79 NQR for uncoordinated Br– ions in trans-[CoBr2(en)2][H5O2]Br2
Authors: Sasane A. , Matsuda T. , Honda H. , Mori Y.
Published: February 2015

A single 79Br NQR line showing a frequency of 19.594 MHz at room temperature has been observed in the crystals of trans-[CoBr2(en)2] [ H5O2 ] Br2 and assigned to the Br - ions which are not coordinated to the central Co(III) atom. The electric field gradient (EFG) at the Br - nuclei arises from O-H • • • Br - hydrogen bond formation between the Br - ions and the terminal O - H hydrogen atoms in [ H5O2 ] + ions. The induced EFG is greater for the present bromine complex than that for the isostructural chlorine complex. A point charge model calculation explains well the relative magnitude of the EFG in the two crystals by introducing Sternheimer's antishielding factors for the halogen ions.
35Cl NQR and Structural Studies of Chloroacetanilides C6H3Cl2NHCOCH3-xClx, 1 ≤ x ≤ 3
Authors: Groke Dirk , Dou Shi-Qi , Weiss Alarich
Published: February 2015

The temperature dependence of 35Cl NQR frequencies and the phase transition behaviour of chloroacetanilides (N-[2,6-dichlorophenyl]-2-chloroacetamide, -2,2-dichloroacetamide, -2,2,2-trichloroacetamide) were investigated. The crystal structure determination of N-[2,6-dichlorophenyl]- 2-chloroacetamide leads to the following: a = 1893.8 pm, b = 1110.7 pm, c = 472.1 pm, space group P212121 = D2
4 with Z = 4 molecules per unit cell. The arrangement of the molecules and their geometry is comparable to the high temperature phase of the acetyl compound N-[2,6-dichlorophenyl]- acetamide. For N-[2,6-diclorophenyl]-2,2,2-trichloroacetamide it was found: a = 1016.6 pm, b = 1194.3 pm, c = 1006.7 pm, ß= 101.79°, space group P21/c = C5
2h, Z = 4. The structure is similar to the low temperature phase of N-[2,6-dichlorophenyl]-acetamide. Parallelism between the temperature dependence of the 35C1 NQR lines of the CCl3 group and the X-ray diffraction results concerning the different behaviour of the chlorine atoms was observed. The structures of the compounds show intermolecular hydrogen bonding of the N - H • • • O - C type. The phenyl group and the HNCO function are nearly planar.

A bleaching out of several 35Cl NQR lines at a temperature far below the melting point of the substances was observed. The different types of chlorine atoms (aromatic, chloromethyl) can be distinguished by their temperature coefficients of the 35Cl NQR frequencies. All the resonances found show normal "Bayer" temperature behaviour.

N-[2,6-dichlorophenyl]-2,2-diehloroacetamide shows several solid phases. One stable low temperature phase and an instable high temperature phase (at room temperature) were observed. The different phases were detected by means of 35Cl NQR spectroscopy and thermal analysis
Electric Field Effect on 14N NQR in Ferroelectric Thiourea Single Crystals
Authors: Kim Hae Jin , Han, Kee Tae , Choh Sung Ho
Published: February 2015

The electric field effect on 14N NQR in ferroelectric thiourea [SC(NH2)2] single crystals has been investigated at 77 K up to a field of 10 kV/cm. The measured Stark shifts are, in units of kHz • cm/ kV, dv1
+ / dE + = 0.87±0.10, dv1
+dE_ = 1.17±0.20, dv2
+/dE+ = 0.80±0.10, and dv2
+/dE_ = 0.90 ±0.15. These values are on the order of 102 times those found in other ferroelectric crystals such as sodium nitrite (NaNO2 ) . The remarkable difference between these two Stark shifts is discussed by taking into account the polarizability and the local electric field at the 14N sites in these crystals
Reorientational Motion of Trihalogenomethyl Groups in Organic Compounds as Studied by 35Cl NQR and 19F NMR Spectroscopy
Authors: Wigand Silvia , Asaji Tetsuo , Nakamurac Daiyu
Published: February 2015

Trihalogenomethyl derivatives of 4-chloroacetanilide, 4-ClC6H4NHCOCCl3,4-ClC6H4NHCOCF2Cl, and 4 - ClC6H4NHCOCF3 were prepared. The 35Cl NQR and 79FNMR spin-lattice relaxation times T1Q and T1F, respectively, of these compounds were measured at various temperatures. On heating, T1Q of the CCl3 and CF2Cl groups decreased rapidly above ca. 110 and 150 K, respectively, showing the onset of reorientation of the trihalogenomethyl group about the pseudo-triad axis. The activation energies were determined to be 27 and 13 k J mol-1 for the CCl3 and CF2Cl reorientation, respectively. The temperature dependences of the 19F NMR T1F of the CF2Cl and CF3 groups lead to activation energies of 13 and 4.3 kJ mol-1 , respectively, for the same reorientations. T1F of the CF3 group observed above ca. 200 K was attributed to the spin-rotational interaction. The T1Q
-1 of ring-chlorine in 4 - ClC 6H4NHCOCCl3 and 4 - ClC6H4NHCOCF3 can be interpreted by the Tn law with n = 2.2 and 1.1, respectively, whereas that of 4-ClC6H4NHCOCF2Cl by the sum of two contributions: Tn law (n = 2.0) and the modulation mechanism due to the CF2Cl reorientation
Anomalous Temperature Dependence of the 99Tc Quadrupole Coupling and Disordering of Cesium Positions in CsTcO4
Authors: Tarasov V. P. , Kirakosyan G. A. , German K. E.
Published: February 2015

A 99T c and 133Cs solid-state NMR study of polycrystalline CsTcO4 at a field of 7.04 T and temperatures from 90 to 430 K revealed first-order quadrupole effects. 99T c quadrupole coupling constant, C
q
, shows anomalous positive temperature coefficients and decreases from 2.0 MHz at 430 K to 0.45 MHz at 90 K. The asymmetry parameter, η (99Tc) , is zero at 430 K and at 210 K. The high-temperature minimum of η is associated with a phase transition from orthorhombic to tetragonal and the second minimum reflects an orientational change of the principal axes qxx and qyy of the EFG-tensor.

The 133Cs NMR spectra are characterised by a superposition of the two powder multiplets from the first-order couplings which arise from magnetically and crystallographically nonequivalent cesium sites, Cs (1) and Cs (2); the population ratio of Cs (2) and Cs (1), p2/p1 , varies from 2.0 at 120 K to 6.5 at 373 K. The nonequivalence and population changes are attributed to the temperature change of the crystal field potential in the vicinity of the cations.
35Cl NQR and Molecular Motion in Solid C6X5Cl (X = H, F)
Authors: Gordeev A. D. , Soifer G. B. , Zhukov A. P.
Published: February 2015

The 35Cl NQR frequency and spin-lattice relaxation time of solid chlorobenzene and chloropentafluorobenzene at temperatures from 77 K to the melting points have been measured and explained by thermoactivated librations and reorientations of the molecules around the normal to their plane. The activation energies of these motions have been estimated
2 D Methods in NQR Spectroscopy
Authors: Seliger J. , Blinc R.
Published: February 2015

The application of two-dimensional spectroscopy to nuclear quadrupole resonance (NQR) is reviewed with special emphasys on spin 3/2 nuclei. A new two-dimensional level crossing double resonance NQR nutation technique based on magnetic field cycling is described. This technique allows for a determination of both the electric quadrupole coupling constant and the asymmetry parameter for spin 3/2 nuclei in powdered samples even in cases where the quadrupolar signals are too weak to be observed directly. It works if the usual double resonance conditions are met, i.e. if the spin-lattice relaxation times are not too short if the quadrupolar nuclei are dipolarly coupled to "strong" nuclei. Variations of this techique can be also used for 2 D "exchange" NQR spectroscopy and NQR imaging.
Contribution of Microwave Fourier Transform Spectroscopy to the Investigation of Nuclear Quadrupole Coupling
Authors: Dreizler Helmut
Published: February 2015

By simple examples it is shown how fine structures in rotational spectra of free molecules can be used to analyse nuclear quadrupole coupling. It is demonstrated that microwave Fourier transform spectroscopy is an adequate tool for these studies. Examples for different nuclei illustrate the present possibilities
Two-dimensional Exchange Spectroscopy Using Pure NQR
Authors: Rommel E. , Nickel P. , Rohmer F. , Kimmich R.
Published: February 2015

Exchange between positions with different resonance frequencies can be studied by two-dimensional spectroscopy originally developed for the NMR case. Cross intensity reflects changes of the resonance frequency due to different line shifts or anisotropic interactions. We now present analogous experiments carried out with pure NQR of polycrystalline samples. The specific requirements are discussed in comparison to 2D exchange NMR spectroscopy. The method has been demonstrated with chloroform and p-chlorobenzotrichloride, where the resonances of the 35Cl nuclei were investigated. Isomeric changes taking place in these compounds reveal themselves as cross-peaks provided the right ranges of the temperature and the mixing time are chosen. The corresponding dependences were recorded and are discussed.
Zeeman NQR Studies on Polycrystals of Copper Compounds, Arsenic Compounds, and Chlorine Compounds
Authors: Ege Osamu , Hamai Sanyo , Negita Hisao
Published: February 2015

Powder Zeeman NQR (PZNQR) spectra of 63Cu,75As, and 35Cl in various compounds have been observed at 77 K. On the basis of the types of simulated integral curves of PZNQR absorption, the estimated asymmetry parameters of the electric field gradients have been divided into three classes; (1) measurable, (2) small (smaller than about 0.05), and (3) very small (probably zero). The asymmetry parameters have been found to be very small ( Cu, NQR frequency = 26.704 MHz) in Cu,0;0.40 (63Cu, 32.617 MHz) in KCu(CN)2; very small (75As, 116.820 MHz) in As2O3 ; very small (75As, 78.950 ; 35Cl, 25.0567 and 25.4036 MHz) and small ( 35Cl, 24.9581 MHz) in ASCl3 ; very small (75As, 98.501 and 99.046 MHz) in As(C6H5)3; small (38.389 MHz), 0.15 (38.464 MHz), and 0.14 ( 38.503 MHz) for 35Cl in hexachlorobenzene; small ( 35.847 MHz) and very small ( 39.154,39.603 , and 39.615 MHz) for 35Cl in l-chloro-2-(trichloromethyl)-benzene; small ( 32.619 MHz) and very small ( 32.878 MHz) for 35Cl in 1,4-dichlorobutane; very small ( 37.828 and 38.051 MHz) for 35Cl in 1,1,1 -trichloroethane.
Experimental Investigations of the Strong Off-Resonant Comb (SORC) Pulse Sequence in 14N NQR
Authors: Kim S. S. , Jayakody J. R. P. , Marino R. A.
Published: February 2015

The behavior of induction signals during steady-state pulse irradiations in 14N NQR was investigated experimentally. It has long been known that the signal response to a long sequence of η pulses will dramatically increase for pulse spacings less than T2. This increase is exponential, and can result in signals comparable to optimally prepared Free Induction Decays. Because these "SORC" signals recur as long as the pulsing continues, very efficient signal-averaging can result. The dependence of these quasi steady-state signals on pulse parameters and on frequency offset are presented, together with a discussion of the applicability of the method.
Recent Development of Nuclear Quadrupole Resonance Spectra Database
Authors: Chihara Hideaki , Mano Koichi
Published: February 2015

The Nuclear Quadrupole Resonance Spectra (NQRS) Database contains all the numerical data of resonance frequencies that have been published since 1950, the year NQR was discovered, through the end of 1989. The total number of records compiled is 10,155 as of May, 1991. One record usually covers data of a particular polymorphic modification of a crystalline substance. About 3/4 of all the records deal with organic or organometallic substances. Recent changes in the data content and format, development of online and stand-alone search software, statistics of the database, and updating problems are described. A personal computer version of the database with load/search software was prepared and is described in the Appendix
Feynman-Kleinert's Treatment of a Class of Harmonic-Oscillators
Authors: Bentaiba M. , Chetouani L. , Hammann T. F.
Published: February 2015

The Feynman-Kleinert method is applied to the harmonic oscillator class of potentials obtained through the factorization method. It is found that the free energy is in good agreement with the exact energy of the harmonic oscillator
1H NMR Studies on Cationic Motions in Solid tert-Butylammonium Hexachlorostannate (IV)
Authors: Ishida Hiroyuki , Higashiyama Tatsuo , Hayama Naomi , Ikeda Ryuichi
Published: February 2015

The temperature dependences of the 1H spin-lattice relaxation time (T1) and the second moment (M2) of NMR absorptions were measured for anhydrous tert-butylammonium hexachlorostannate(IV) and its partially deuterated analogs [(CD3)3CNH3]2SnCl6 and [(CH3)3CND3]2SnCl6. Three kinds of cationic motions were revealed: the reorientations of the CH3 group about their C - C bonds, the NH+
3 group about its C - N bond, and the tert-butyl group about the C - N bond. Their motional parameters were determined. Among the three motions, the NH+
3 motion occurs at the lowest temperature with quite a small activation energy (9.9-10.0 kJ mol-1 ) .
Differential Thermal Analysis and Dielectric Studies on Neopentanol under Pressure
Authors: Kreul H. G. , Waldinger R. , Würflinger A.
Published: February 2015

Differential thermal analysis (DTA) and dielectric measurements have been performed on 2,2-dimethyl- 1-propanol (neopentanol) up to 200 MPa. Neopentanol exhibits at least one orientationally disordered (ODIC) phase (solid I) that transforms at lower temperatures to a non-plastic phase (solid II). There is evidence of a further ODIC phase denoted as solid I'. The pressure dependence of the phase transitions and the dielectric behaviour up to frequencies of 13 MHz are described. Activation enthalpies and volumes are derived from the dielectric relaxation time and compared with results for other alcohols
Lattice Vibration Spectra. LXXV. IR Single Crystal Reflection Spectra of Sr(ClO3)2
Authors: Lutz H. D. , Schmidt M.
Published: February 2015

Polarized infrared reflection spectra of Sr(ClO3)2 single-crystal plates are recorded and analysed for the frequencies of the transversal and longitudinal optical zone-centre phonon modes and other oscillator parameters by Kramers-Kronig analyses and both the classical 3 parameter (dielectric sum-function) and the 4 parameter (factorized form) oscillator-fit methods. The frequencies computed are compared with the results of previous single-crystal Raman studies. Because of the great distortion of the ClO3
- ions (site symmetry C1, no intraionic coupling of the CIO vibrations to symmetric ( ν 1) and asymmetric (ν3) stretching modes occurs. The TO/LO splittings of respective CIO unit-cell group modes rank like the vector elements of the corresponding CIO bonds with respect to the crystal axe
FTIR Study of the v12 and the v12 + v14 — v14 Bands of 1,3,5-Triazine Near 740 cm-1
Authors: Bodenmüller Wolfram , Ruoff Andreas , Manceron Laurent
Published: February 2015

The infrared spectrum of the v12 fundamental and its accompanying hot band v12 + v14 - v14 of triazine has been measured by means of a Fourier transform spectrometer with a resolution of about 0.0023 cm-1 . A total of about 2779 rovibrational transitions has been assigned. The ground state constants have been considerably improved whilst the parameters for the excited states v12 = 1, v14 = 1 and v12 = v14 = 1 have been obtained for the first time. The standard deviations were 2.92 • 10-4 cm-1 for the ground state constants and 1.53 • 10-4 cm -1 for the excited state parameters of v12 showing the latter to be unperturbed. The upper state of the hot band v12 + v14 - v14 was found to be perturbed by an accidental resonance.
Rayleigh-Taylor Instability of a Partially Ionized Plasma in a Porous Medium in Presence of a Variable Magnetic Field
Authors: Sharma R. C. , Sunil
Published: February 2015

The Rayleigh-Taylor instability of a partially ionized plasma in a porous medium is considered in the presence of a variable magnetic field perpendicular to gravity. The cases of two uniform partially ionized plasmas separated by a horizontal boundary and exponentially varying density, viscosity, magnetic field and neutral particle number density are considered. In each case, the magnetic field succeeds in stabilizing waves in a certain wave-number range which were unstable in the absence of the magnetic field, whereas the system is found to be stable for potentially stable configuration/stable stratifications. The growth rates both increase (for certain wave numbers) and decrease (for different wave numbers) with the increase in kinematic viscosity, medium permeability and collisional frequency. The medium permeability and collisions do not have any qualitative effect on the nature of stability or instability.