bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Nuclear Quadrupole Interaction of 199mHg-Cysteine and 199mHg-tert-butyl-mercaptide
Authors: Butz T. , Tröger W. , Pöhlmann Th. , Nuyken O. 
Published: February 2015

Abstract
The nuclear quadrupole interaction of 199mHg in Hg-cysteine and Hg-tert-butyl mercaptide was determined at room temperature by perturbed angular correlations. The dramatic difference in the interaction strength between both compounds is a result of the two-fold and four-fold sulfur coordination, respectively. Moreover, we compared the preparation of Hg-cysteine using a Hg: cysteine ratio of 1:2 and using carrier-free 199mHg from ISOLDE/CERN and obtained identical results.
The Nuclear Quadrupole Moments of the 20 First Elements: High-Precision Calculations on Atoms and Small Molecules
Authors: Pyykkö Pekka 
Published: February 2015

Abstract
The available values of the nuclear quadrupole moments for the elements H - Ca are reviewed and related to recent advances in numerical methods in quantum chemistry. For Li the quantum chemical and nuclear Coulomb scattering values now agree. For Mg, also the muonic result agrees with them. For Na and Al, the new, accurate atomic values deviate from the earlier muonic values
Ab initio Calculations of the Electric Field Gradients in Solids in Relation to the Charge Distribution
Authors: Schwarz Karlheinz , Blaha Peter 
Published: February 2015

Abstract
A first principles method for the computation of electric field gradients (EFGs) is illustrated for various solids. This scheme is based on self-consistent energy band-structure calculations by the full potential linearized augmented plan wave (FLAPW) method which provides the electronic charge density including all polarization effects. By numerically solving Poisson's equation we obtain the Coulomb potential in a form which allows to compute the EFG directly. Our method is demonstrated for insulators (Cu2O), metals (hcp-Zn), supercondutors (YBa2Cu3O7 ) and molecular crystals (Cl2, Br2 , I2).
Milli-Kelvin NQR: A Study of the Praseodymium Trihalides
Authors: Armstrong Robin L. , Su Sunyu 
Published: February 2015

Abstract
Milli - Kelvin NQR experiments are often essential for the study of pseudo one-dimensional materials. A brief overview of the special technical consideration for carrying out NQR measurements in a dilution refrigerator is given. Recent halide quadrupole resonance experiments on the pseudo one-dimensional XY crystals PrCl3 and PrBr3 are reviewed including the measurement and interpretation of frequencies, and spin-lattice relaxation times.
Chlorine Nuclear Spin-Spin Relaxation Mechanism in Mg(H2O)6SnCl6 as Studied by NQR and NMR Techniques
Authors: Horiuchi Keizo , Nakamura Daiyu 
Published: February 2015

Abstract
The 35Cl NQR spin-lattice relaxation time T1Q, spin-spin-relaxation time T2Q, and 1H NMR spin-lattice relaxation time in the rotating frame T1Q in Mg(H2O) 6SnCl6 were measured as functions of temperature. Above room temperature T2Q increased rapidly with increasing temperature, which can be explained by fluctuations of the local magnetic field at the chlorine nuclei due to cationic motions. From the T1Q experiments, these motions are found to be attributable to uniaxial and overall reorientations of [Mg(H2O)6 ] 2 + ions with activation energies of 95 and 116 kJ mol - 1 , respectively. Above ca. 350 K, T1Q decreased rapidly with increasing temperature, which indicates a reorientational motion of [SnCl6] 2 - ions with an activation energy of 115 kJ mol -1 .
Reorientation of the CCl3 Group in Chloral 4-Chlorobenzylhemiacetal. A Pulsed 35Cl NQR and X-ray Study
Authors: Hashimoto Masao , Isono Takahiro , Yomesaka Noriko , Niki Haruo , Kyan Hiroshi , Hamagawa Takeshi 
Published: February 2015

Abstract
The crystal structure of the title compound was determined at 291 K : monoclinic, space group C5
2h-P21/n, Z = 4, a = 1693.2(1), b = 579.3(1), c = 1232.5(1) pm, and ß = 107.21 (1)°, R = 0.0415. A sharp decrease of of Cl NQR found at T ≳ 270 K for the CCl3 group is attributed to the reorientation of the group over a potential barrier of ca. 50 kJ/mol. Intermolecular interactions between the CCl3 and the neighboring atoms seem to dominate the magnitude of the potential barrier. T1
-1 of the 35Cl NQR of the Cl atom on the benzene ring obeyed the T2 law well in the range 80 ≲ T/K ≲ 270, while at T ≳ 280 K it deviated from the T2 law.
Quadrupole Hyperfine Structure in the Rotational Spectra of Sulfur Dichloride
Authors: Merke Ilona , Dreizler Helmut 
Published: February 2015

Abstract
The nuclear quadrupole coupling of [35Cl,35Cl]- and [35Cl,Cl]-sulfur dichloride was investigated using waveguide microwave Fourier transform (MWFT) spectroscopy. The analysis was performed with direct diagonalization of the Hamilton matrix. Due to some measured transitions with near degeneracy it was possible to determine the off diagonal elements χab of the quadrupole coupling tensor with high accuracy.
S35Cl2: χ aa (35Cl1) = χaa(35Cl2) = -38.671(11) MHz, χcc(35Cl1) = χcc(35Cl2) = 47.7945(66) MHz, χab(35Cl1) = -χab( Cl2) = ± 53.76(23) MHz.
S35Cl36Cl: χaa(35Cl) = -37.756(13) MHz, χcc(35Cl) = 47.7915(75) MHz, χab(35Cl) = ± 54.018(83) MHz, χ aa(35Cl) = -31.217(13) MHz, χcc (37Cl) = 37.6759(66) MHz,
χab ( 37 Cl ) = + 42.285(98) MHz.
We also determined the quadrupole coupling constants in their principal axes system. In comparison with the restructure the z-axis of the coupling tensor was found to be tilted 1.3° out of the S - Cl bond axis
Debye-Waller Type Expressions for the Nuclear Elastic Form Factors at Small Momentum Transfers
Authors: Grypeos M. E. , Lalazissis G. A. , Massen S. E. , Panos C. P. 
Published: February 2015

Abstract
The problem of estimating the nuclear elastic form factors in Born approximation is discussed in the region of small momentum transfers q. It is shown that approximate expressions of the Debye-Waller type are suitable for estimates of these form-factors in the oscillator shell model for sufficiently small q and compare favorably with other simple expressions.
Structure of Supercooled Aqueous Zinc(II) Bromide Solutions by Raman and X-Ray Scattering Methods
Authors: Takamuku Toshiyuki , Yoshikai Kazumasa , Yamaguchi Toshio , Wakita Hisanobu 
Published: February 2015

Abstract
The structure of aqueous zinc(II) bromide solutions with [H2O/[ZnBr2] molar ratios 5 and 10 in the supercooled state and at ambient temperature has been investigated by Raman spectroscopy and X-ray scattering. Raman spectra of glassy solutions have also been measured for comparison. The Raman and X-ray data suggest that tetrabromo and hexaaqua zinc(II) complexes are favoured in the supercooled and glassy state, while dibromo- and tribromozinc(II) complexes are formed as main species in the solutions at ambient temperature. Probably the reactions

and

occur in the supercooled and glassy solutions. These equilibrium shifts are discussed.
The Microwave Spectra and Nitrogen Quadrupole Coupling Constants of Cyano- and Isocyano-pentafluorobenzene
Authors: Krüger Michael , Dreizler Helmut 
Published: February 2015

Abstract
The microwave spectra of cyano-pentafluorobenzene, C6F5CN, and isocyano-pentafluorobenzene, C6F5NC , have been assigned by molecular beam microwave Fourier transform spectroscopy. The 14N nuclear quadrupole coupling constants have been determined for both isomers
Conformational Aspects of Substituents in Enamines. X-Ray Structure Analyses and Quantum Chemical Calculations
Authors: Raabe Gerhard , Karl Wolfgang , Enders Dieter , Fleischhauer Jörg 
Published: February 2015

Abstract
X-ray structure determination of the enamine (Z)-4-(6'-t-butoxycarbonyl-2',2'-dimethyl-5'-phenyl- 3'-hexen-3'-yl)morpholine (1) reveals that certain bulky groups may enforce a relative orientation of the molecular subunits without conjugative interaction between the nitrogen lone pair and the olefinic double bond. According to the results of quantum chemical ab initio calculations the experimentally found arrangement would be the least favourable one in the absence of such substituents. A careful analysis of the molecular structure of 1 shows that this unusual arrangement is due to the presence of both, the a- and the ß-substituent.
In (E)-4-(3'-t-butoxycarbonylmethyl-1'-phenyl-1'-penten-1'-yl)morpholine (2) rather the nitrogen lone pair than the phenyl n system is in conjugation with the olefinic double bound. The results of ab initio calculations on model compounds show that conjugation of the double bond with the nitrogen lone pair is by 2 - 6 kcal/mol more favourable than conjugative interaction between the phenyl group and the C = C bond. Closer examination of the molecular structure of 2, however, led to the conclusion that it is predominantly the ß-substituent which forces the phenyl ring in a position where conjugation with the enamine double bond is not possible
A Photophysical Study of Tri-chromophoric Systems Containing Two Naphthalene Moieties: Intramolecular Excimer Fluorescence, Energy Transfer, Phosphorescence, and Delayed Fluorescence
Authors: Gundermann Karl-Dietrich , Romahn Elke , Zander Maximilian 
Published: February 2015

Abstract
Photophysical properties of 9,10-di[(l-naphthyl)-methyl]-9,10-dihydro-9,10-phenanthrenediol (1), 9,10-di(l-naphthyl)phenanthrene (2), 9,10-di(2-naphthyl) phenanthrene (3), 10,10-di(1 -naphthyI)- 9,10-dihydro-9-phenanthrone (5 a) and 10,10-di(2-naphthyl)-9,10-dihydro-9-phenanthrone (5 b) have been studied. In contrast to l,4-di(l-naphthyl)butane compound 1 shows strong (intramolecular) excimer fluorescence in dilute solution at room temperature. As a result of intramolecular triplettriplet energy transfer the phosphorescence of 2, 3, 5 a and 5 b stems from the naphthalene moieties. The increase (compared to naphthalene) of the rate constant of the radiative deactivation of the lowest triplet state is probably due in the case of 2 and 3 to the non-planarity of the molecules, which is expected to increase spin-orbit coupling, while in compounds 5 a and 5 b intramolecular chargetransfer interaction between the carbonyl group and the naphthalene moieties may be responsible for this effect. Delayed fluorescence (from the phenanthrene moiety) of 2 has been observed in fluid solution at room temperature, and an excitation mechanism is proposed
Luminescence Spectra of the Mixed Chloro-Bromo-Technetates(IV), [TeClnBr6-n]2-n=1-5
Authors: Wendt A. , Preetz W. 
Published: February 2015

Abstract
The Γ7(2T2t) Γ8(4A2g) luminescence spectra of mixed Cs2[TcClnBr6-n, n= 1-5, in various host crystals have been measured between 14 000 and 12 800 cm-1 at 10 K. For the first time host lattices have been doped with purely isolated chloro-bromo-technetates(IV), including the geometrical isomers with n = 2, 3, 4. The assignments of the electronic transitions and their extensive vibronic structure are discussed.
Crystal Structures and 35Cl NQR Spectra of the Metastable and the Stable Phase of Guanidinium bis-Monochloroacetate, [C(NH2)3 ]⊕[(ClH2C)COOH ••• OOC(CH2Cl)l⊖
Authors: Basaran Reha , Dou Shi-qi , Weiss Alarich 
Published: February 2015

Abstract
From acid aqueous solutions of guanidinium carbonate and monochloroacetic acid, (ClH2C)COOH :H2 NC( = NH)NH2 ≧ 2.5, the compound [C(NH2)3]⊕ [(ClH2C)COOH • • • OOC(CH2Cl)]⊖ crystallizes with the space group Ci
1P1̄,Z = 4, a = 1147.4 (5) pm, b= 1113.2 (5) pm, c = 876.5 (4) pm, α = 88.66 (2)°, β = 80.31 (2)°, γ = 84.41 (2)° (metastable phase I). Cooled to 77 K once, phase I transforms at room temperature slowly into the stable phase II, orthorhombic, D2h
15 - Pbca, Z = 8, a= 1299.2 (4) pm, b= 1533.7 (4) pm, c= 1073.9 (3) pm. The crystal structure determinations show for both phases an ionic lattice with guanidinium cations [C(NH2)3]⊕ and acid bis-(monochloroacetate) anions [(ClH2C)COOH • • • OOC(CH2Cl)]⊖ in which a monochloroacetic acid molecule and a monochloroacetate ion are bound to the dimer anion by an asymmetric hydrogen bond O-H • • • O.
A strong crystal field effect, much dependent on temperature, is observed in the 35Cl NQR quadruplet spectrum of phase I, with a frequency spread of ≈4 MHz at 300 K, whereas in phase II the frequency splitting of the observed 35Cl NQR doublet is almost constant between 77 K and 310 K, about 700 kHz. The phase transition I → II is very sluggish and unidirectional. The transition II → I needs the recrystallization of II from water.
Structure and dynamics of the two solid phases are discussed.
Viscosity B Coefficients of Some Tetraalkylammonium Bromides, Lithium Tetrafluoroborate and Tetrabutylammonium Tetraphenyl borate in Propylene Carbonate
Authors: Muhuri Prakash K. , Hazra Dilip K. 
Published: February 2015

Abstract
The viscosities of solutions of tetraalkylammonium bromides, R4NBr (R = -C2H5 to -C7H15), lithium tetrafluoroborate (LiBF4) and tetrabutylammonium tetraphenylborate (Bu4NBPh4) in propylene carbonate (PC) have been measured at 25, 35 and 45 °C. The relative viscosities have been analyzed using the Jones-Dole equation in the form of unassociated electrolytes, and the viscosity B-coefficients have been evaluated. The thermodynamic parameters have been calculated using the transition-state treatment and the measured temperature dependencies. Ionic B values have also been derived and discussed in terms of Einstein's equation. The analysis shows that Li+ is highly solvated compared to other cations and anions in this medium.
Fluorescence Anisotropies of 4-Dimethylamino-ω- diphenylphosphinyl-trans-Styrene in Isotropic Media in the Case of One-and Two-Photon Excitation
Authors: Kawski A. , Gryczyński J. , Gryczyński Z. 
Published: February 2015

Abstract
Fluorescence emission anisotropies, r, and mean lifetimes of 4-dimethylamino-ω-diphenylphosphinyl-trans-styrene (DDPS) were measured in n-butanol at different temperatures from 20 to 80 °C for one-and two-photon excitation. When increasing the temperature, the lifetime decreased from 32 to 12 ps, the r values, however, remained constant (0.315 and 0.445 for one-and two-photon excitation, respectively) and were found to be temperature independent. For DDPS in glycerol at - 5°C, where rotational diffusion does not occur during the excited state lifetime, the limiting emission anisotropies were r0 = 0.382 and r0 = 0.545 for one-and two-photon excitation, respectively, very little differing from the fundamental emission anisotropies rf = 2/5 and rf = 4/7. The small differences rf - r0 can be due to vibrations performed after excitation by the DDPS molecule as a result of the initial shock.
Nuclear Quadrupole Hyperfine Structure and Methyl Torsional Fine Structure in the Rotational Spectra of N,N-Dimethylformamide and N-Nitrosodimethylamine
Authors: Heineking N. , Dreizler H. 
Published: February 2015

Abstract
The complicated nuclear quadrupole hyperfine structure and methyl torsional fine structure in the rotational spectra of N,N-dimethylformamide and N-nitrosodimethylamine have been studied using microwave Fourier transform spectroscopy. It has been found that both molecules are rather similar in terms of their parameters of methyl group internal rotation as well as in terms of their amino nitrogen quadrupole coupling constants.
"Anomalous" Thermal Conductivity of Crystalline Alkali Halides Close to Their Melting Point
Authors: Khokhlov V. A. , Kodintseva A. O. , Filatov E. S. 
Published: February 2015

Abstract
The thermal conductivity of crystalline alkali halides MX (M = Li, Na, K, Rb, and Cs; X = C1, Br, and I) close to their melting point has been measured by the steady-state coaxial-cylinders method. It was found to change anomalously as the temperature varied. A minimum of the thermal conduc-tivity at a characteristic temperature depends on the ionic composition of the crystal. This effect is ascribed to the formation of cooperating defects in the melting lattice. An expression relating the thermal conductivity of the ionic crystal near the melting point to the concentration of these defects is proposed.
Isomerization of Diphenyl Polyenes.Part IV. Evidence for Two Luminescent Conformers of 1,4-Diphenyl-1,3-butadiene in Poly(vinyl alcohol) Films
Authors: Kawski A. , Kukliński B. , Kubicki A. , Piszczek G. 
Published: February 2015

Abstract
Investigations of the effect of the excitation light wavelength on the intensity distribution in the fluorescence band of 1,4-diphenyl-1,3-butadiene (DPB) in poly(vinyl alcohol) films (PVA) at 296 and 87 K for samples before and after heating to 423 K, and fluorescence lifetime measurements have shown that trans-trans and cis-trans conformers are responsible for the emission of fluorescence. The fluorescence properties of the DPB sample in PVA heated to 423 K were found to be similar to those of DBP in polyvinyl chloride and polyvinyl formal at 296 K.
The Thermal Diffusivity of Quasicrystalline Al72 Pd20Mn8 Alloy
Authors: Ohta H. , Tsai An-Pang , Inoue A. , Masumoto T. 
Published: February 2015

Abstract
A new cell has been developed for measuring the thermal diffusivity of small samples [about (5 x 2 x 0.5) mm3], using the laser flash method. The thermal diffusivities of small samples of titanium, SUS304 and Pyrex 7740 glass measured with this cell agree well with those obtained from samples of 10 mm in diameter and 0.4 mm in thickness. Then, the thermal diffusivity between 300 K and 950 K of quasicrystalline Al72Pd20 Mn8 with a single domain size of 5 mm, and that of crystalline Al60Pd25 Mn15 were measured. The thermal diffusivity of quasicrystalline Al72 Pd20 Mn8 was found to be 4 to 7 times smaller than that of crystalline Al60Pd25Mn15 .
Steady State Photolysis and Product Analysis of 4-Chloroanisole in Aqueous Solutions
Authors: Abd El-Hameed Faten S. M. , Krajnik Paul , Getoff Nikola 
Published: February 2015

Abstract
Aqueous solutions of 4-Chloroanisole (4ClA) of various concentrations saturated with Ar, N2O, air, and O2 were photolyzed under steady state conditions using uv-light of 228.8 and 253.7 nm. The reaction products (4-methoxyphenol, 4-chlorophenol, anisole and hydroquinone) were detected by HPLC. Mechanisms which account for these photoproducts are suggested.
Neglect of Diatomic Differential Overlap (NDDO) in Non-Empirical Quantum Chemical Orbital Theories
Authors: Koch Wolfhard 
Published: February 2015

Abstract
The possibility of a drastic reduction of electron repulsion and nuclear attraction integral evaluations occurring in non-empirical quantum chemical orbital methods of Hartree-Fock and configuration interaction type is discussed. Simplification schemes are proposed and examined in consideration of useful numerical applications.
Electron Density and Anharmonic Thermal Atomic Vibrations in K1_ xLixTaO3 (x=0, 0.05, 0.15) Perovskites
Authors: Zhurova E. A. , Zavodnik V. E. , Ivanov S. A. , Syrnikov P. P. , Tsirelson V. G. 
Published: February 2015

Abstract
The results of accurate X-ray diffraction studies of KTaO3 , K0,95Li0,05TaO3 and K0,85Li0,15TaO3 crystals are presented. Anharmonicity of the thermal motion of the oxygen atoms and deformation electron density maps are discussed.
Weak Reflections in the Laves Phase FeBe2
Authors: Margarida M. , Costa R. , de Almeida Maria José B. M. , Paixão José António 
Published: February 2015

Abstract
X-ray diffraction intensities from a single crystal of the Laves phase FeBe 2 were collected at room temperature. Atomic and thermal parameters as well as a scale factor were determined by least-squares refinements of high-angle data [(sin θ)/λ ≥ 0.6Â-1].
The results of Fourier inversion of the data are presented in terms of maps of the total density and followed by a discussion of the "effects" of two criteria for labelling reflection intensities as "unobserved", based on their statistical accuracy.
Electron Deformation Density at Temperatures around 20 K
Authors: Zobel Dieter , Luger Peter , Dreißig Wolfgang 
Published: February 2015

Abstract
A 20 K difTractometer for X-ray measurement is described. Electron density experiments at 15 K for oxalic acid and at 23 K for acetamide were carried through, leading to high-resolution experi-mental and multipole static density maps.
Entropy Maximizations on Electron Density
Authors: Collins Douglas M. 
Published: February 2015

Abstract
Incomplete and imperfect data characterize the problem of constructing electron density representations from experimental information. One fundamental concern is identification of the proper protocol for including new information at any stage of a density reconstruction. An axiomatic approach developed in other fields specifies entropy maximization as the desired protocol. In particular, if new data are used to modify a prior charge density distribution without adding extraneous prejudice, the new distribution must both agree with all the data, new and old, and be a function of maximum relative entropy. The functional form of relative entropy is s = - r In (r/t), where r and t respectively refer to new and prior distributions normalized to a common scale.
Entropy maximization has been used to deal with certain aspects of the phase problem of X-ray diffraction. Varying degrees of success have marked the work which may be roughly assigned to categories as direct methods, data reduction and analysis, and image enhancement. Much of the work has been expressed in probabilistic language, although image enhancement has been somewhat more physical or geometric in description. Whatever the language, entropy maximization is a specific and deterministic functional manipulation. A recent advance has been the description of an algorithm which, quite deterministically, adjusts a prior positive charge density distribution to agree exactly with a specified subset of structure-factor moduli by a constrained entropy maximization.
Entropy on an N-representable one-particle density matrix is well defined. The entropy is the expected form, and it is a simple function of the one-matrix eigenvalues which all must be non-negative. Relationships between the entropy functional and certain properties of a one-matrix are discussed, as well as a conjecture concerning the physical interpretation of entropy. Throughout this work reference is made to informational entropy, not the entropy of thermodynamics.
Preliminary Results of a 20 K X-Ray Study of Citrinin
Authors: Destro R. , Merati F. 
Published: February 2015

Abstract
A total of about 37 000 diffracted intensities has been measured at 20 K for a spherical single crystal of citrinin. Using a multipole formalism to interpret the X-ray data, maps of the charge density and of its Laplacian, as well as for the electrostatic potential have been derived. A value of 7(2) D has been obtained for the magnitude of the molecular dipole moment. A study of the electric field gradient (EFG) at the nuclei has yielded the atomic quadrupole coupling constants (QCC) and asymmetry parameters (η). A topological analysis of the charge density has been performed to characterize the intramolecular covalent and hydrogen bonds.
Experimental and Theoretical Spin Densities in Two Alkyl Nitroxides
Authors: Bordeaux D. , Boucherleb J. X. , Delley B. , Gillon B. , Ressouehe E. , Schweizer J. 
Published: February 2015

Abstract
The spin density in the two alkyl nitroxide compounds 4-oxo-and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (tempone and tempol) has been determined by polarised-neutron diffraction and compared to theoretical predictions obtained in both the Unrestricted Hartree-Fock and the Local Spin Density approaches.
Spin Densities in Copper-Nitronyl Nitroxide Complexes
Authors: Boucherle J.-X. , Ressouche E. , Schweizer J. , Gillon B. , Rey P. 
Published: February 2015

Abstract
The spin density in two copper-nitronyl nitroxide complexes, viz. bis(hexafluoroacetylacetonato)-(2,4,4,5,5-pentamethyl-l-oxy-imidazoline 3-oxide)-copper(II) and dichloro-bis(2-phenyl-4,4,5,5-tetra-methyl-l-oxy-imidazoline 3-oxide)-copper(II), has been determined by polarised-neutron diffrac-tion. Spin populations and unpaired electron wave functions have been refined.