bluuebunny/crossref_metadata_2025_split huggingface dataset:
The 33S Nuclear Quadrupole Coupling in the Rotational Spectrum of Methylthiirane
Authors: Lorenzo Felipe , Alonso José L. , Grabow J.-U. , Dreizler H. 
Published: February 2015

Abstract
As a first example in a series of substituted thiiranes we present an investigation of the nuclear quadrupole coupling in 33S-methylthiirane in natural abundance. The rotational and quadrupole coupling constants are: A = 11 599.0976(18) MHz, B = 4815.6822(6)MHz, C = 3909.1318 (5) MHz, χaa = -12.7731 (82) MHz, χbb = -20.3366(118) MHz, χcc = 33.1097(273) MHz.
Analysis of Internal Rotation and Determination of the Heavy Atom Structure of anti-2,3-Dimethylthiirane by Fourier Transform Microwave Spectroscopy
Authors: Hartwig Holger , Dreizler Helmut 
Published: February 2015

Abstract
We used the advanced technique of Fourier transform microwave spectroscopy to measure and assign the ground state rotational spectrum of anti-2,3-dimethylthiirane, and to analyse the internal rotation of the two methyl groups. The potential parameters obtained are V3 = 13.1678(21) and V12
' = -1.6678(25) kJ/mol. The measurement and assignment of the 13C and 34S isotopomers in the ground state allowed to determine the molecular structure of the heavy atom frame using the Τs and Τ0 methods.
The 33S Nuclear Quadrupole Coupling in the Rotational Spectrum of 2,2–Dimethylthiirane
Authors: Grabow Jens-Uwe , Onda Masao , Dreizler Helmut 
Published: February 2015

Abstract
The rotational spectrum of 33S 2,2-dimethylthiirane with its 33S nuclear quadrupole coupling hyperfine structure in the range 8.9 to 20.0 GHz and its analysis is reported. The rotational constants are A = 5507.4663(3), B = 3440.58395(18), and C = 2978.5723(3) MHz. The 33 S quadrupole coupling constants are χaa = -22.6390(23), χbb = 47.1830(50), and χcc = -24.5440(50) MHz.
Die Lösung der Schrödinger-Gleichung als eindimensionales Problem. IV. Erfassung von Korrelation am Beispiel der Zweielektronensysteme He und H2
Authors: Pernpointner M. , Preuß H. 
Published: February 2015

Abstract
After calculating ground and excited states of one-electron systems with improved discretization methods in Part III of this work it is shown that also correlation contributions can be yielded by this formalism. The more powerful discretization methods are applied to the two-electron systems He and H2. For multi-electron systems the symmetry properties of the wave function become important but in the case of two-electron systems an antisymmetric spin part can be separated and the integral kernel containing the spatial part of the wavefunction has therefore to be symmetric.
Additions of Cyclopentadiene to a Dissymmetric Maleic Anhydride: Semiempirical Calculations of Their Thermodynamics and Kinetics
Authors: Kuo Liang-Hsuan , Slanina Zdenĕk , Chou Teh-Chang 
Published: February 2015

Abstract
There are four conceivable products of the title addition, however only two of them have been prepared. MNDO, AM1, and PM3 quantum-chemical computations have been used in order to rationalize the observation. Activated complexes have been computed for the four possible additions and it was found that one C-C bond rather than two is created on the path from the reactants to the activated complex (the C-C bond varies between 1.70 and 1.87 A). Only one activated complex has been localized on each reaction path. The two types of products observed in experiment are computed to be both thermodynamically more stable and kinetically more feasible, and hence the computations agree with the observations.
Langjährige Be7 -Bodenluftmessungen lassen Änderung des atmosphärischen Austauschverhaltens während der letzten Jahrzehnte vermuten
Authors: Hartwig S. 
Published: February 2015

Abstract
An analysis covering three decades (1964-1994) of monthly Be7 ground-level-air concentration measurements at Braunschweig shows a systematic trend of the data. This trend is related to the yearly maximum/minimum concentration ratio. The observation may be due to a continuous mitigation of exchange processes between stratosphere and troposphere. This finding is commensurate with the hypothesis that, due to the growing concentration of anthropogenic infrared active gases, the heat source distribution in the stratosphere and consequently the eddy diffusivity and exchange process between stratosphere and troposphere are altered. This results in a shorter irradiation period of stratospheric air portions by cosmic rays and consequently can lower the concentration of isotopes of stratospheric origin in ground level air.
Notiz: Sulphate Rotator Phases in Polarised Light
Authors: Tärneberg Roy 
Published: February 2015

Abstract
Li2SO4 has a well defined high-conducting fee phase in the temperature range 577-860 °C, and LiNaSO4 a bcc phase in the range of 518-614 °C. Both salts were studied in polarised light during sequences going from melt, through the cubic phase into the "room temperature" phase, and back to the cubic phase. The two cubic sulphate phases are compared with organic plastic rotator phases, especially regarding the formation of vapour snakes.
New Unsaturated 1,8-Naphthalimide Dyes for Use in Nematic Liquid Crystals
Authors: Grabtschev Ivo K. , Moneva Ivanka T. , Wolarz Eryk , Bauman Danuta 
Published: February 2015

Abstract
The properties of new fluorescent dyes (derivatives of unsaturated 1,8-naphthalimide) are stud-ied. Spectral characteristics of the dyes are recorded in both isotropic (ethanol, dioxane) and anisotropic (nematogenic liquid crystal mixture ZLI 1840) media. The optical, electro-optical, and thermodynamical properties of the liquid crystal-dye mixtures are examined. The orientational order parameters are evaluated to be within 0.4 -0.5, depending upon the dye's molecular structure. Additionally, the influence of chemical bounding of the dyes to polystyrene chains on the phase transition temperature from the nematic to the isotropic state of polymer / liquid crystal mixtures is investigated. The low-molecular-mass dyes do not markedly affect the clearing point of pure liquid crystal, while the dye-styrene copolymers lower the transition temperature and widen the two-phase region at the transition. The electro-optical properties of the dye / liquid crystal systems imply potential utilization of the dyes studied in the so called "guest-host" liquid crystal displays.
Crystal Structure Refinement and Single Crystal 81Br Zeeman NQR Study of KHgBr3· H2O
Authors: Terao Hiromitu , Okuda Tsutomu , Uyama Sachiyo , Negita Hisao , Dou Shi-qi , Fuess Hartmut , Weiss Alarich 
Published: February 2015

Abstract
Three 81Br NQR resonance lines of KHgBr3 ·H2O were detected between 77 K and room temperature. From the Zeeman effect measurement on a single crystal the nuclear quadrupole coupling constants (e2qQ/h) and the asymmetry parameters (ƞ) were obtained, which are 228.42 MHz and 0.005, 226.24 MHz and 0.005, and 108.76 MHz and 0.465 for e2qQ/h and ƞ at 295 K, respectively. Large deviations of the observed directions of electric field gradient tensors from the directions expected from previous X-ray results have been found. With the present X-ray redetermination, 81Br NQR and structure are in good agreement. The structure and bonding in the compound are discussed.
The Structure of a Zn(II) Metaphosphate Glass. I. The Cation Coordination by a Combination of X-Ray and Neutron Diffraction, EXAFS and X-Ray Anomalous Scattering
Authors: Bionducci M. , Licheri G. , Musinu A. , Navarra G. , Piccaluga G. , Pinna G. 
Published: February 2015

Abstract
In order to clarify the reason of some discrepancies existing in literature, the zinc coordination in a Zn metaphosphate glass has been investigated by the complementary use of X-Ray Diffraction, Neutron Diffraction, Extended X-ray Absorption Fine Structure Spectroscopy and X-Ray Anoma-lous Scattering. All the techniques indicate a tetrahedral coordination of O atoms around Zn :+ ions, the Zn-O distance being 1.94 ± 0.01 Å. The simultaneous modelling of all the experimental data by Reverse Monte Carlo technique demonstrated that this coordination is consistent with an extended model in which metal ions are interposed between phosphate chains. The importance of describing the preparation conditions of the glasses is stressed when structural results have to be compared.
Association in Molten Salts and Mobility Isotherms showing the Chemla Effect
Authors: Klemm Alfred , Schäfer Lutz 
Published: February 2015

Abstract
In 1984 a model for additive binary molten salt mixtures had been proposed that allowed for a qualitative understanding of the occurence of the Chemla effect (equal internal mobilities at a certain mixing ratio of the salts). In that model the presence of three ions (1,2 and 3) and two neutral molecules (4 and 5) consisting of two ions is assumed, and the ratios K1 = x4 / x1x3 and K2 = X5 / X2X3 of their mole fractions are assumed to be independent of the mixing ratio of the salts. In the present paper, that model is compared with recent experimental results on the system (Li, Cs)Cl obtained in Japan. The comparison shows that the model is too simple for a quantitative description of systems showing the Chemla effect. Rather a dependence of K1 and K2 on the mixing ratio of the salts must be assumed.
A Unified Mechanism for the Production of ZEKE States
Authors: Held A. , Baranov L. Ya. , Selzle H. L. , Schlag E. W. 
Published: February 2015

Abstract
ZEKE states are highly stabilized Rydberg states which exist below each ionic eigenstate of a molecular system even high up into the continuum. The stability and neutrality of these states is the basis on which the high resolution ZEKE technique for the study of molecular ions is built upon. A new mechanism is proposed for the production of ZEKE states from optically accessible, relatively short lived Rydberg states. The mechanism is based on experimental results for a range of fields and ion concentrations. The experiments were performed with pulsed and static electric fields of different magnitudes at various ion concentrations.
The Rationale of Trouton's Rule and of the Trouton-Hildebrand-Everett Rule
Authors: Logan S. R. 
Published: February 2015

Abstract
In seeking a rational basis for the general rules regarding the enthalpy of vaporisation of a liquid, it is shown that whereas Trouton's Rule is consistent with the assumption that the effective molar volume, v, for translational motion in the liquid is a constant fraction (2 x 10-5) of the molar volume of vapour at 1 atm, the rather better approximation of Trouton, Hildebrand and Everett (THE), which corrects for the effects of varying molecular density in the vapour, re-quires that v be 1.5 cm3 mol-1 for all substances. The introduction of the apparently more reasonable assumption that v is a constant fraction of the molar volume of the liquid, is shown to lead to an expression exhibiting much poorer cor-relation. It thus offers no improvement to Trouton's rule nor to the THE rule.
Zeeman Transitions in Low Magnetic Field: Dependence of Line Shapes on the Asymmetry Parameter for Spin ≥ 3/2 Systems
Authors: Stephenson David , Smith John A. S. 
Published: February 2015

Abstract
Transitions between the Zeeman levels of spin 3/2 systems have been detected in low magnetic fields (ca. 25 mT) via the dynamic solid effect. Transitions are detected at frequencies vP ± vQ , where vQ corresponds to the Zeeman splitting of the ± 1/2 and/or the ± 3/2 levels in the small applied field, and vP is the proton NMR frequency. Using this approach, the line shape for polycrystalline samples can be recorded with a good signal-to-noise ratio despite the low frequencies involved. Computer calculated line shapes are also presented, which show that the asymmetry parameter can be obtained from the experimental spectra.
Rapid Measurement of Nutation NQR Spectra in Powders Using an RF Pulse Train
Authors: Sinyavsky Nicolai , Ostafin Michał , Maćkowiak Mariusz 
Published: February 2015

Abstract
The method of two-dimensional nutation NQR spectroscopy, introduced by Harbison in 1989, has been successfully used for determining of the asymmetry parameter of the EFG tensor for spin-3/2 nuclei in both powdered and monocrystal samples in the absence of an external magnetic field. The inconvenience inherent in the method, however, is the long time required, because data acquisition must be repeated for various RF pulse lengths. We discuss a method to reduce the time of the nutation experiment by using a sequence of identical short RF pulses of length r w and distance τ. It is shown that for an NQR frequency ω0 , frequency offset Δω, and pulse parameters satisfying the relation ω0τ + Δωtw = 2πk (k = 1, 2, 3,..., n) a synchronism of pulse action takes place and the nutation interferogram can be measured "stroboscopically" between the pulses. The maximum time saving factor that can be obtained as compared to the conventional nutation experiment is of the order of the number of pulses used in a pulse train. The method has been successfully applied for determination of the asymmetry parameter for one of the two 3 5 Cl sites in polycrystalline 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride).
Measurement of Nuclear Quadrupole Interactions using Mössbauer Spectroscopy
Authors: Cook Desmond C. 
Published: February 2015

Abstract
Mössbauer spectroscopy is a useful probe for investigating nuclear quadrupole interactions. It enables the magnitude, sign and asymmetry of the electric quadrupole coupling constant to be determined. It is especially important for its ability to measure these parameters for excited nuclear states. The Mössbauer effect is used to measure excited state quadrupole moments in materials whose electric field gradient (EFG) is known. More commonly however, it is used to determine the EFG from which atomic bonding and electronic structure are determined. The technique also allows temperature dependent orientation of sublattice magnetization to be measured using the direction of the electric quadrupole coupling as a reference.
Molecular Origin of Glass Forming Tendency in Ternary Te-Se-Br(Cl) Chalcohalide Glasses
Authors: Bresser W. J. , Wells J. , Zhang M. , Boolchand P. 
Published: February 2015

Abstract
Bulk glasses of Te3 _zSez-(CI or Br)2+y , the composition spanning the glass forming range, were characterized by differential scanning calorimetry, 125Te absorption, and 129I emission Mössbauer spectroscopy. The results reveal that the stoichiometric glasses Te3(Cl or Br)2 consists of c-Te3 Cl2 -like chain fragments about 1.5 nm long and terminated by one-fold coordinated halogen atoms. The 125Te electric hyperfine structure results reveal that Te replacement by Se (z ≠ 0) leads to preferential occupancy at those Te sites in the chains that are two-fold coordinated, and in a rather striking fashion demonstrate that the average length of the chain fragments remains independent of Se concentration. Halogen atoms in the glasses act as chain terminators, and also bond to Te-sites in the chains to produce four-fold coordinated sites. The low glass transition temperatures (Tg
~ 70 -90°C), the low average coordination number of the proposed chain-fragments, along with the hyperfine structure results, suggest that the extensive glass forming tendency in the chalcohalides derives from the floppiness of the chain-fragments.
Mössbauer Effect in Biomedical Research: Variations of Quadrupole Splitting in Relation to the Qualitative Changes of Biomolecules
Authors: Oshtrakh M. I. 
Published: February 2015

Abstract
This review deals with studies of the variations of quadrupole splitting, electronic structure and stereochemistry of iron associated with qualitative changes of biomolecules. The possibility to determine various iron containing species resulting from the destruction of biomolecules using Mössbauer parameters is shown. A small change of iron stereochemistry leads to a small change of the iron electronic structure which could be detected by small changes of quadrupole splitting. It is expected that quadrupole splitting of iron gives new information for biomedical research on a molecular level.
Mössbauer Spectroscopy Evidence for Phase Selectivity in Excimer Laser Induced Amorphization of Thermally Annealed FeCoBSi Metallic Glass
Authors: Sorescu M. , Knobbe E.T. 
Published: February 2015

Abstract
Pulsed excimer laser irradiation effects (λ = 308 nm, τ = 10 ns, w = 3 J/cm2 , N = 2 laser pulses/spot, repetition rate 1 Hz) on the magnetic properties and phase composition of thermally annealed Fe66Co18B15Si1 metallic glass have been studied by transmission and conversion electron Möss-bauer spectroscopy (CEMS). Radiation-driven surface modifications were examined by scanning electron microscopy (SEM). Excimer laser induced amorphization was observed in partially crystallized Fe66Co18B15Si1 samples (T A = 648 K, t A = 1 hour) and was found to be accompanied by the development of laser-induced magnetic anisotropy. In totally crystallized Fe66Co18B15Si1 specimens (T A = 723 K, = 1 hour), the effect of excimer laser induced amorphization exhibited phase selectivity with respect to the crystalline components of the alloy system. When compared to bulk data, a different behavior of the surface magnetic texture and relative abundance of alloy phases was observed. The laser-induced phase transformation of thermally annealed Fe66Co18B15Si1 specimens was shown to consist of partial amorphization and surface oxidation of the irradiated material.
Nuclear Quadrupole Interactions Studied by Time Differential Perturbed Angular Correlations of γ-Rays
Authors: Butz T. 
Published: February 2015

Abstract
This paper gives an elementary introduction to time differential perturbed angular correlation of γ-rays emitted from excited nuclei with particular reference to nuclear quadrupole interactions. We start with a comparison to other techniques such as nuclear quadrupole resonance and the Mössbauer effect, quote all necessary formulae, describe a typical spectrometer, list suitable isotopes, and finally give some examples for modern applications.
Bayes’ Theorem Applied to the Selection of Models in PAC
Authors: Hemmingsen Lars , Hansen Steen 
Published: February 2015

Abstract
Using Bayes’ formula, the parameters in a given model fitting data from perturbed angular correlation of γ-rays (PAC) experiments are all integrated out, giving as the result the total proba-bility for the model. Experimental examples are given from PAC for models containing one and two nuclear quadrupole interactions, respectively. It is shown how the Bayesian formulation leads to a quantification of the probability of the correctness of the models. Furthermore, this method leads to a transparent and intuitively appealing criterion for model selection. Examples are given using PAC measurements on two proteins: liver alcohol dehydrogenase and azurin.
Hg-Coordination Studies of Cysteine Containing Oligopeptides
Authors: Tröger W. , Lippert C. , Schmidt P. , Schmidt U. , Butz T. , Hoffmann R. , Zeppezauer M. , Isolde  
Published: February 2015

Abstract
In order to study the interaction of cysteine containing peptide chains with Hg(II) the nuclear quadrupole interaction (NQI) of 199mHg in the Hg complex of the oligopeptide Alanine-Alanine-Cysteine-Alanine-Alanine (AACAA) was determined by time differential perturbed angular correla-tion. Different 199mHg-NQI’s for free and resin-bound AACAA were obtained. Furthermore, the 199mHg-NQI’s are influenced by the Hg:AACAA stoichiometry.
PAC Studies of Ag-Hf Intermetallic Compounds
Authors: Wodniecki P. , Wodniecka B. , Marszałek M. , Hrynkiewicz A. Z. 
Published: February 2015

Abstract
The hyperfine quadrupole interaction of 181Ta and 111Cd probes in HfAg and HfiAg com-pounds was studied at 24 to 1100 K with the time -differential perturbed angular correlation (TDPAC) technique. The EFGs measured in HfAg on 181Ta and 111Cd are 1.388(5)x1018 Vcm-2 and 0.340(5)x1018 Vcm -2 , respectively. For both probe atoms a linear decrease of the EFG with temperature was observed with slopes 1.11(2)x10-4 K-1 and 1.73(5)x10-4 K-1 for 181Ta and 111Cd, respectively. In Hf2 Ag, 0.469(2)x1018 Vcm-2 was determined on 181Ta nuclei and 0.428(5)x1018 Vcm-2 on 111Cd. Also a linear EFG temperature dependence with the large slope of 2.39(6)x10-4 K-1 was observed for 111Cd probes in Hf2Ag, while the EFG measured on 181Ta nuclei in this compound exhibits a very weak temperature variation which can be fitted neither with a linear T nor a T 3/2 dependence. In all cases the electronic contributions to the EFG are very small indicating that these transition element systems do not obey the universal correlation between the electronic and the ionic EFG observed in numerous other systems not belonging to the transition metal series.
17O Nuclear Quadrupole Coupling in Molecular and Lattice Systems by ab initio Calculation of Electric Field Gradients
Authors: Palmer Michael H. 
Published: February 2015

Abstract
We present ab initio Hartree-Fock calculations of electric field gradients, which are related to experimental determinations of nuclear quadrupole coupling constants. The nucleus of special interest is 17O but other nuclei in the molecules, especially 14N, 2H and 33S are included. The calculations were performed (a) as single molecules either at the SCF and MP2 correlated levels, (b) as clusters of molecules about a test site, or (c) as lattice calculations computed in the unit cell environment. The basis sets are triple zeta valence plus polarisation in (a). Because of limitations in exponent range in (c), the bases in both (b) and (c), where comparison was sought, are DZ at the SCF level.
Quadrupole Coupling in Purines and Pyrimidines by Hartree-Fock Lattice Calculations of Electric Field Gradients
Authors: Palmer Michael H. 
Published: February 2015

Abstract
We present ab initio Hartree-Fock lattice calculations on adenine, guanine and hypoxanthine, and some pyrimidines, including cytosine and uracil derivatives. The electric field gradients at the nitrogen centres are related to NQR experimental determinations of nuclear quadrupole coupling constants. The calculations were performed as lattice calculations in the unit cell environment, with 6-31G or double zeta basis sets at the SCF level. The present analysis strongly suggests that χzz at N3 in cytosine, N3 in guanine are both positive, and approximately tangential to the ring at that centre. In contrast, N7 in guanine is like most other azine-type N centres, with a largely radial direction for χzz. The 3-protonated cytosine ring has χzz as the local π-direction.
Ab-initio Band Structure Calculations and 61 Ni-Mössbauer Studies of BaNiO2 , BaNiO3 and CaNiN
Authors: Hannebauer B. , Schmidt P.C. , Kniep R. , Jansen N. , Walcher D. , Gütlich P. , Gottschall R. , Schöllhorn R. , Methfessel M. 
Published: February 2015

The electron density distribution of the nickel compounds BaNiO2 , BaNiO3 and CaNiN has been investigated experimentally by 61Ni Mössbauer spectroscopy and theoretically by band structure calculations using the FP-LMTO (Full Potential Linear Muffin-Tin Orbital) method. For all compounds good agreement is found between the experimental and theoretical values of the electric field gradient qexp. and qtheor. at the nickel site.
BaNiO2 contains nickel in a square-planar coordination forming puckered chains of edge-sharing NiO4 squares. |q| at nickel is large: qexp = - 15.7(1.5) • 1021 Vm-2 and qtheor. = - 15.59 • 1021 Vm-2 .
The principal axis z is perpendicular to the NiO4 squares. The crystal structure of BaNiO3 contains face-sharing chains of NiO6 octahedra. In BaNiO3 q(Ni) is small: qexp. = ± 3.6(2.0) • 1021 Vm-2 and qtheor. = - 1.86 • 1021 Vm-2 . Because of the small broadening of the Mössbauer resonance line the sign of q could not be determined experimentally.
The nitridoniccolate CaNiN contains infinite linear chains 1
∞[NiN2/2 ] which run perpendicular to the c axis. Unexpectedly, |q(Ni)| in CaNiN is small: qexp. = 0.0 (2.0) • 1021 Vm-2 and qtheor. = - 3.05 • 1021 Vm-2. Again the sign of q(Ni) could not be determined experimentally. It is found theoretically that the small value of q(Ni) is caused by severe cancellation between σ and π contributions.