bluuebunny/crossref_metadata_2025 huggingface dataset:
Onset of Buoyancy and Surface-Tension Driven Instabilities in Presence of Random Vibrations
Authors: Dandapat B. S.
Published: February 2015

Onset of thermal convection in an incompressible fluid layer bounded between a perfectly heat conducting lower rigid plate and an upper free surface is analysed when the layer is subject to random vibrations. It is shown that when the vibrations are characterized by a white noise process, they hasten the onset of convection. Further it is shown that the stability zone is demarcated by an inverted parabola in the (R, M) plane.
An EPR Investigation of Cr3+ and Ni2 + in Synthetic Pyrite Crystals
Authors: Siebert D. , Miller R. , Fiechter S. , Dulski P. , Hartmann A.
Published: February 2015

In many synthetic pyrite single crystals of high quality and purity we could detect Cr3 + and Ni2 + by EPR at 78 K as unwanted impurities. The assignment was possible by means of the isotopes Cr53 and Ni61, occurring in natural abundance. The paramagnetic centers exhibit unusual g-values. In case of Ni2 + a ligand hyperfine interaction could be observed beside the normal hyperfine interaction with the Ni61 nucleus. For some crystals the Cr 3 + signal intensity could be increased up to ten times by temperature increasement from 78 K to about 100 K. At 78 K the Cr3 + intensity was quenched by IR irradiation.
A High Pressure Pulsed Expansion Valve for Gases, Liquids, and Supercritical Fluids
Authors: Köster C. , Grotemeyer J. , Schlag E. W.
Published: February 2015

A novel design of a pulsed valve for coupling chromatographic techniques with gaseous and liquid mobile phases to a time-of-flight mass spectrometer with multiphoton ionization (MUPI) is presented. The valve can be operated in low pressure regions ( <10 bar) up to temperatures of 350 °C and at higher pressures (300 bar) up to temperatures of 200 °C. Pulse widths lower than 100 μs could be measured. First results demonstrate the ability of interfacing of liquid chromatography to MUPI-mass spectrometry. Additional coupling of CO2-laser desorption to the valve allows the interface to be used for mass spectrometric measurements of nonvolatile biomolecules.
Kathodo- und Photolumineszenz der Seltenerd-aktivierten Granatsysteme Y3-xGdxM2GaGe2O12 (M = Mg, Zn)
Authors: Wiehl J. , Kemmler-Sack S.
Published: February 2015

The optical properties of the self-activated garnet systems Y3-x GdxM2GaGe2O12 (M = Mg, Zn) activated with Ce, Pr, Eu, Tb are strongly influenced by an energy transfer between defect centers of the host and the activator ions. The luminescence properties are studied as a function of the parameter x for M = Mg, Zn.
Tautomerism in Five-membered Nitrogen Heterocycles. A Test of the Reliability of Semiempirical (AMI, PM3, MNDO) Quantum Chemical Methods
Authors: Fabian Walter M. F.
Published: February 2015

The reliability of three popular semiempirical quantum chemical methods (AM1, PM3, MNDO) for the treatment of tautomeric equilibria is tested in a series of five-membered nitrogen heterocycles. The known flaw of MNDO to overestimate the stability of compounds with two or more adjacent pyridine-like lone pairs is also present in AM1 and to a somewhat lesser extent in PM3. Tautomeric species differing in the number of adjacent pyridine-like lone pairs, thus, cannot be adequately treated by these semiempirical methods. Both AM1 as well as PM3, however, represent major improvements over MNDO in the case of lactam-lactim tautomerism. The stability of N-oxides as compared to N-hydroxy tautomers seems to be overestimated by the PM3 method. All three semiempirical methods yield quite reliable ionization potentials and dipole moments.
Topological Characteristics of Strictly Pericondensed Constant-Isomer Benzenoid Series
Authors: Ray Jerry
Published: February 2015

Our previous constant-isomer series are supplemented and extended. Two distinct classes of constant-isomer benzenoid groups have been identified. One class is topologically unique and the other one forms a pairwise topologically equivalent class
The 63,65Cu NQR Spectra of Di-coordinated CuI Cations with 2-Substituted Pyridine Ligands
Authors: Habiyakare Augustin , Lücken Edwin A. C.
Published: February 2015

The NQR frequencies of the 63,65 Cu nuclei in di-coordinated complex cations of Cu 1 , having the general formula CuL 2X, where L is a substituted pyridine and X is a hard anion such as ClO4 , are reported and discussed in the light of the known crystal structures. A departure from a strictly linear geometry of the L 2 Cu cation has but little effect on the resonance frequency, but the donor-acceptor bond between the nitrate anion and the copper atom in bis(2,6-lutidine)cuprous nitrate, which was postulated on crystallographic grounds, is confirmed by the NQR results, which also indicate a similar interaction in bis(2,6-lutidine)cuprous trifluoroacetate. A number of the complexes discussed here have not been reported previously.
Investigation of the C-Cl Bonds in Trichloroacrylic Acid, Cl2C = CClCOOH, by Single Crystal Zeeman Split NQR
Authors: Wulfsberg Gary , Weiden Norbert , Weiss Alarich
Published: February 2015

The 35Cl NQR spectrum of trichloroacrylic acid, Cl2C = CClCOOH, was studied by single crystal Zeeman NQR spectroscopy at 303 K (high temperature phase I) and at 275 K (low temperature phase II). At 303 K for the = CCl2 group chlorines it was found eQΦzz h-1(35Cl(2)) = 76.179 MHz, η (35Cl) = 0.1597; eQΦzz h -1 (35Cl(3))= 74.693 MHz, η(35Cl) = 0.1868 and for the = CClC - group chlorine eQΦzz h -1(35Cl(1)) = 75.145 MHz, η (35Cl) = 0.1568. The difference in the electric field gradients at the stereochemically inequivalent chlorines Cl(2) and Cl(3) is rather large. The asymmetry parameter η (35Cl(1)) shows an unusual temperature dependence which probably originates from the change of the hydrogen dynamics and position within the dimeric H-bonded unit (Cl2C = CClCOOH)2 during the phase transition
Elementary Excitations in Order-Disorder Systems Studied by NQR
Authors: Milia F. , Papavassiliou G. , Giannakopoulos E.
Published: February 2015

The 35Cl spin-lattice and spin-spin relaxation times T1 and T2 as functions of temperature and impurity concentration were analytically calculated and experimentally verified for the incommen-surate phase of [Rb1-x (NH 4)x]2 ZnCl4 . The results agree with the theoretical predictions for both the amplitude and Goldstone modes of fluctuations.
81Br and 127I NQR and Phase Transitions in CH3NH3 HgBr3 and CH3NH3 HgI3
Authors: Terao Hiromitsu , Okuda Tsutomu
Published: February 2015

The 81Br and 127I NQR spectra were recorded in CH3NH3 HgBr3 and CH3NH HgI3 , respectively. In addition to a phase transition at 338 K, successive phase transitions take place at 127 ± 1, 184±1 and 243±5 K in CH3NH3 HgBr3. On heating, the resonance lines of CH3NH3HgI3 disappear near a phase transition at 328 K and one line appears above this temperature. The temperature variations of the resonance frequencies of the terminal halogen atoms in both crystals are extraordinarily steep. This indicates the large amplitude molecular motions expected for the CH3NH3 cations which are linked to the terminal halogen atoms through N-H ··· X type H-bonding.
N Nuclear Quadrupole Resonance Study of the Phase Transitions of Ba[Fe(CN)5NO]·3H2O
Authors: Murgich Juan , Bonalde Ismardo , Abanero Jose A.
Published: February 2015

The 14N nuclear quadrupole resonance (NQR) of the cyanides in Ba[Fe(CN) s NO] · 3H2O (BNP) was observed between 77 and 293 K. Phase transitions exist at 118,131 (both weakly first order) and 233 K (second order). Most of the cyanides were perturbed by the structural changes except for one of the trans cyanides that was only affected by the transition at 131 K. The mechanism of the phase transitions is interpreted in terms of soft modes resulting from the ion rearrangement produced by the slowing down of the water molecules upon cooling. A comparison of the NQR spectrum of BNP with that of Na2[Fe(CN)5NO] · 3H2O showed that the substitution of Na+ by Ba2+ produced only minor changes in the charge distribution of the nitroprusside ion.
The ab initio Calculation of Nuclear Quadrupole Coupling Constants and their Comparison with Experiment
Authors: Palmer Michael H.
Published: February 2015

Ab initio calculations of electric field gradients (EFG) and conversion to nuclear quadrupole coupling constants (NQCC) are described, with particular reference to 14 N and 10,11B. The correlation of EFG and NQCC for a series of boranes leads to the value 8.32 MHz/a.u. (0.0354 barn) for Q(11B).

The structural variations of these microwave and single molecule calculations of 10,11 B NQCC are discussed.
A Study of High Tc Oxide Superconductors by NQR and NMR Measurements
Authors: Asayama K. , Kitaoka Y.
Published: February 2015

Results of NQR, NMR and nuclear relaxation measurements in normal and superconducting states of high Tc superconductors, (La1-x Sr(Ba)x)2 CuO4 , YBa2Cu3O7, (Bi - Pb)2Sr2Ca2Cu3O10 , Tl2Ba2Ca2Cu3O10 and (Nd1-xCex)2 CuO4 are reviewed.
Fade-Out of 35Cl NQR in Chloral n-Butylhemiacetal
Authors: Hashimoto Masao , Isono Takahiro , Niki Haruo , Higa Takuya
Published: February 2015

Continuous wave and pulsed NQR, dielectric absorption and infrared (IR) measurements were carried out to investigate the origin of the peculiar temperature dependence of the S/N ratio of the 35Cl NQR in the title compound. The dielectric and IR experiments evidenced a thermally activated jumping motion of the H atom participating in O-H O H-bonds. As T1 and T2 below 120 K were much longer than T*2 of about 10 μs, the line broadening in this temperature region was attributed to static lattice defects. A random freezing of the jumping motion may be the origin of the defects. In the range 120-170 K, S/N was extremely low and T2 was less than 10 μs, probably having a minimum in between. The short T2 is considered to be responsible for the low S/N. A minimum of S/N at about 240 K is attributed to a T1 minimum (less than 10 (μs) at that temperature.
Chlorine Nuclear Quadrupole Relaxation due to the Motion of Pyridinium Cations in Pyridinium Hexachlorometallates(IV): (pyH)2 MCl6 (M = Sn, Pb, Te)
Authors: Tai Yutaka , Asaji Tetsuo , Nakamura Daiyu
Published: February 2015

The temperature dependence of the chlorine quadrupole spin-lattice relaxation time T1Q was observed for one of the three 35Cl NQR lines of (pyH)2 MCl6(M = Sn, Pb, Te). Each T1Q curve can be devided into three temperature regions. In the low-and high-temperature regions, T1Q is dominantly determined by the relaxation mechanism due to the libration and reorientation of [MCl6]2- , respectively. In the intermediate temperature region, T1Q results from the modulation of the electric field gradient by the motion of the neighboring pyridinium cations. This way the reorientational motion of the cation between potential wells with nonequivalent depths is precisely characterized.
Lattice Imperfections and Relaxation of Cl NQR in Chloral Iso-Butylhemiacetal
Authors: Niki Haruo , Igei Ryokan , Higa Takuya , Hashimoto Masao , Isono Takahiro
Published: February 2015

The temperature dependence of the S/N ratios of three 35Cl NQR lines (v1, v2 , v3) in chloral iso-butylhemiacetal shows interesting features in the range 77-300 K. 35Cl T1 indicates that above 220 K reorientation of CCl 3 is excited, and this results in a gradual decrease in S/N. The activation energy calculated from 35Cl NQR T1 results is 30 kJ mol-1 for v1 and v2 but 25 kJ mol -1 for v 3 . The difference seems to be attributable to the motion of H in the OH group. A minimum of 35Cl NQR T2 is found around 180 K but 35Cl T1 shows no anomaly. 35Cl T2 determines the S/N ratios in the range between 130-220 K. The line broadening below 130 K is attributable to an inhomogeneity of the electric field gradient at resonant nuclei produced by lattice defects.
Nuclear Quadrupole Coupling Tensors of 2H in the a-Alum RbAl(SO4)2 · 12D2O and the Dynamical Behaviour of the D2O Molecules. An Investigation by NMR and IR
Authors: Ramakrishna J. , Weiden Norbert , Weiss Alarich
Published: February 2015

By single crystal NMR the nuclear quadrupole coupling constants eQΦzz h-1 (2H), the asymmetry parameters η(2H) and the direction cosines of the principal axes of the electric field gradient tensors of the 2H atoms of the two kinds of D2O molecules have been determined at 295 K in RbAl(SO4)2 · 12D2O. The results show that the D2O molecules surrounding the ion Al3+ are “static” within the time scale of the 2H nuclear quadrupole interaction while the D2O belonging to the octahedron around the Rb+ undergoes fast reorientations around the twofold molecular axis. For the two kinds of D2O in the alum we found: eQΦzz
(1)h-1 (2H) = 186.5 kHz, η(1),(2H) = 0.1234; eQΦzz
(2)h-1 (2H) = 169.7 kHz,η (2)(2H) = 0.1297; eQΦzz
(3)h-1(2H) = 122.1 kHz, (2H) = 0.8087. eQΦzz
(1) and eQΦzz
(2) belong to the "static" D2O molecules and an assignment to the two different 2H atoms has been performed. The IR spectra of RbAl(SO4)2 · 12(H1-xDx)2O have been investigated, and for the O - D stretching frequencies values of 2145 cm-1 , 2235 cm-1 , 2470 cm-1 and 2525 cm -1 have been obtained. They agree well with the relations between ṽOD and eQΦzz h-1(2H) given in the literature.
Anomalous Temperature Dependence of Spin-lattice Relaxation Time of the 14N-NQR Line in NaNO2
Authors: Igarashi M. , Eto K. , Saito Y. , Abe Y.
Published: February 2015

The temperature dependence of the 14N-NQR spin-lattice relaxation time T1 of a powder sample of NaNO2 prepared from saturated aqueous solution could be fitted by a monotonic curve. When this sample was annealed, two minima of the T1 -Tcurve appeared around 35 K and 77 K. The origin of this phenomenon is discussed.
35Cl NQR Spin-Lattice Relaxation in Paramagnetic CuPtCl6 · 6H2O
Authors: Mizuno Motohiro , Asaji Tetsuo , Nakamura Daiyu , Horiuchi Keizo
Published: February 2015

35Cl NQR spin-lattice relaxation times T1Q of paramagnetic CuPtCl6 · 6H2O were measured as a function of temperature. Below the cooperative Jahn-Teller phase transition at Tc = 136 K, an almost temperature independent T1Q between 0.6 and 1 ms was obtained for each line of the triplet observed. This suggests that the nuclear spin-lattice relaxation of chlorine is dominantly determined by magnetic dipolar interactions between chlorine nuclei and electron spins. No marked anomaly in the nuclear relaxation rate was detected at T c . Above Tc , T1Q for the single 35Cl NQR line increased from 0.6 ms at Tc to 1-4 ms at 365 K. The rapid T 1Q decrease observed above ca. 390 K can be attributed to a reorientational motion of the [PtCl6]2- anion with an activation energy of 1.1 x 102 kJ mol-1 .
Calculation of NQR v's and T1
-1' s being proportional to T4 and T5 , respectively
Authors: Máckowiak Mariusz , Dimitropoulos Costas
Published: February 2015

The second-order Raman phonon process for a multilevel spin system is shown to give a quadru-polar spin-lattice relaxation rate T1
-1varying as T5 at very low temperatures. This relaxation rate for quadrupole spins is similar to the one discussed for a paramagnetic spin system having a multilevel ground state. The temperature dependence of T1 is discussed on the basis of some simplifying assumptions about the nature of the lattice vibrations in the Debye approximation. This type of relaxation process has been observed below 20 K in tetramethylammonium hydrogen bis-trichloroacetate for the 35Cl T1
-1 . Below 20 K the NQR frequency in the same crystal reveals a T4 temperature dependence due to the induced modulations of the vibrational and librational coordinates by the low-frequency acoustic phonons.
A NQR Study of γ-alumina Containing Chemisorbed Cl2
Authors: Sharma Virendra K. , Richarz Werner , Sharma Surendra , Weiss Alarich
Published: February 2015

Cl2 was adsorbed at 370 and 870 K on commercially available y-alumina, with BET surface area of 180m2/g, after dehydration at 850 K. NQR measurements were carried out between 55 and 6 MHz. The sample containing Cl2 chemisorbed at 870 K showed the presence of a set of quite strong NQR signals with frequencies lower than 10.6 MHz, and another set of very weak NQR signals between 18.5 and 13.0 MHz. The stronger signals have been inferred as due to Al and have been assigned to Al in three distinct environments. The values of e2 Qq/h and η determined for the signals are (1) 35.9 MHz, 0.53; (2) 35.7 MHz, 0.74; and (3) 35.3 MHz, 0.0 respectively. These values of e2 Qq/h are found to be very high as compared to those estimated for 27Al at distorted octahedral and tetrahedral sites of the alumina, viz. 3.5 and 4.0 MHz respectively, from MAS-NMR. Therefore, chemisorption causes 27Al to exist in the surface region at sites with greater distortion than in the interior of the particles but much smaller than in the case of completely dehydrated samples for which no NQR signals could be observed. The weak signals have been tentatively attributed to 35Cl. The present results demonstrate that the NQR technique can be used in studies of chemically bound species on heterogenous catalysts.
NQR in the Effective Fields of a Multiple-Pulse Sequence
Authors: Furman G. B. , Kibrik G. E. , Poljakov A. Yu. , Shaposhnikov I. G.
Published: February 2015

We discuss a new form of resonant response for a quadrupolar nuclear spin system subjected to applied alternating magnetic fields.
Two-dimensional Nutation Echo Nuclear Quadrupole Resonance Spectroscopy
Authors: Harbison Gerard S. , Slokenbergs Andris
Published: February 2015

We discuss two new two-dimensional nuclear quadrupole resonance experiments, both based on the principle of nutation spectroscopy, which can be used to determine the asymmetry parameter, and thus the full quadrupolar tensor, of spin-3/2 nuclei at zero applied magnetic field. The first experiment is a simple nutation pulse sequence in which the first time period (t1) is the duration of the radiofrequency exciting pulse; and the second (t2) is the normal free-precession of a quadrupolar nucleus at zero-field. After double Fourier-transformation, the result is a 2 D spectrum in which the first frequency dimension is the nutation spectrum for the quadrupolar nucleus at zero-field. For polycrystalline samples this sequence generates powder lineshapes; the position of the singularities, in these lineshapes can be used to determine the asymmetry parameters η in a very straightforward manner, η has previously only been obtainable using Zeeman perturbed NQR methods. The second sequence is the same nutation experiment with a spin-echo pulse added. The virtue of this refocussing pulse is that it allows acquisition of nutation spectra from samples with arbitrary inhomogeneous linewidth; thus, asymmetry parameters can be determined even where the quadrupolar resonance is wider than the bandwidth of the spectrometer. Experimental examples of 35Cl, 81Br and 63Cu nutation and nutation-echo spectra are presented.
Numerical Design of Composite Pulses for Polycrystalline Samples in Pulsed NQR Spectroscopy
Authors: Ramamoorthy A. , Narasimhan P. T.
Published: February 2015

The density matrix approach along with fictitious spin-1/2 or tensor operator formalisms were employed to obtain general expressions for and thus the signal induced in a coil in the case of physically equivalent non-interacting spin I = 1 and 3/2 nuclei in a single crystal with a three-pulse composite pulse. The corresponding powder averages were then obtained and the dependence of the signal on the i-th pulse flip angle (θi) and phase (ϕi) studied. A numerical procedure established the optimum "π/2" composite pulse for polycrystalline samples as (90)0 -(70)45 -(20)25 , where the quantity in parentheses denotes the flip angle and the subscript the phase. A two-pulse composite pulse of the form (126)0 -(300)80 was also inferred, but the three-pulse composite pulse is superior. These composite pulses are shown to have general validity for other spin I values.
Modeling of High-Signal Electrostriction. II
Authors: Cieminski J von
Published: February 2015

The predictions obtained with a thermodynamical method are compared with experimental results. Several materials which pass a ferroelectric phase transition of first or second order are investigated. The predictions correspond well with the experimentaly determined qualitative and quantitative features as to the field and temperature dependence. Finally, extraordinary strain-field curves are predicted and proved.
Microwave Spectra of Furazan. III. Rotation Spectra of Vibrationally Excited States
Authors: Stiefvater Otto L.
Published: February 2015

The pure rotational spectra of molecules in 21 vibrationally excited states of the heterocyclic compound furazan (C2H2N2O) have been detected and studied by DRM microwave spectroscopy. Rotational parameters are reported for the 12 fundamental levels below 1500 cm-1 , and the contri-butions from 10 vibrational modes to the effective rotational constants and to the inertia defect of furazan are calculated.
Thallium Nuclear Magnetic Relaxation in Solid Thallium (I) Thiocyanate TlSCN: Phase Transition and Ionic Motion
Authors: Furukawa Yoshihiro , Nakamura Daiyu
Published: February 2015

The NMR spin-lattice relaxation time (T1) and linewidth parameter (T2*) of 203Tl and 205T1 in solid T1SCN were measured from 290 K up to the melting point (Tm = 507 K). The nonexponential magnetization recovery of could be characterized by a short (T1
s) and a long (T1
1) component. T1
1 showed a T-2 dependence below ca. 350 K in the orthorhombic phase (T<Tc = 371 K) and a minimum in the tetragonal phase (Tc<T<Tm), which were interpreted in terms of lattice vibrations and head-to-tail flips of the linear SCN- ions, respectively. A broad minimum of 77 around 360 K was explained in terms of indirect nucleus-electron scalar coupling between 203Tl and 205Tl, modulated via the anionic flips occurring in the symmetric and asymmetric potential fields for the highland low-temperature phase, respectively. The phase transition is closely related to dynamical disorder of the anionic orientations. At higher temperatures, translational self-diffusion of Tl+ was evidenced by the T2* and T1
s results
Multiphoton Ionization of Mixed Benzene-Water-Metanol Clusters. Competitive Microscopic Solvation
Authors: Börnsen K. O. , Selzle H. L. , Schlag E. W.
Published: February 2015

Clusters of benzene with polar molecules are observed from a supersonic jet expansion of a ternary mixture of benzene, water and methanol seeded in Helium. It is found that complex formation with methanol is strongly enhanced when a single water molecule is preadsorbed.
A Deuteron NMR Study on the Dynamics of Fluorobenzene Molecules Adsorbed o nGraphite and Boron Nitride
Authors: Boddenberg B. , Grundke V.
Published: February 2015

The present 2H NMR study gives some evidence that a film of fluorobenzene of about one monolayer thickness on graphite undergoes a 2D phase transition from a fluid like into a rotationally disordered solid phase at ca. 160-130 K, and subsequently a 2D solid-solid transition into an ordered phase at a temperature about 90 K. A multilayer film (Θ= 8) decomposes below about 200 K into a 3 D bulk solid phase and an adsorbed film, of presumably monolayer thickness. It is concluded that the monolayer film spreads uniformly on the available surface with flat orientation of the molecules. These detailed statements can be obtained because the combined action of the intramolecular quadrupole interaction and the extramolecular magnetic shielding type coupling allows to relate the Z-axes of coordinate frames fixed in the support and fixed in the adsorbed molecule.
Molecular Dynamics Study of an Aqueous LiF Solution
Authors: Zhu Sheng-Bai , Wilse Robinson G.
Published: February 2015

The structure and properties of a 1.791 molal aqueous LiF solution is investigated by performing molecular dynamics simulations using a water model with both bond flexibility and instantaneously responsive polarization. On average, each cation is in close contact with about one anion. This causes a strong overlap of the hydration shells and an almost complete breakdown of the surrounding water structure. While the lone pairs of the hydration waters in the first Li+ shell occupy preferentially tetrahedral positions, the orientational distribution of the solvent molecules around F--is quite uniform. By comparing various autocorrelation functions of water molecules in the solution and in the pure liquid, the influence of solvated ions on the translational, rotational and vibrational motions of hydration water can be studied
A Theoretical Study of Fulvene Radical Anions
Authors: Khalil Salim M. , Jarjis Hayfa M.
Published: February 2015

MINDO-Forces calculations have been performed, with complete optimization of geometry on fulvene and X-fulvene radical anions, where X is OH, NH2, CH3, NO,2 CN, F, dimethyl and cyclopropyl. A twisted structure with angle 5° was found for fulvene anion. All substituents are stabilizing. The stabilization effect is more pronounced in the case of NO2, and very weak in the case of CH3. It was found that the substituents CH3 and CN show amphielectronic behaviour. Geometrical parameters, heats of formation, dipole moments, electron and spin densities are reported
Photophysical and Photochemical Studies of Polycyclic Aromatic Hydrocarbons in Solutions Containing Tetrachloromethane. III. Photochemical Interaction of Excited Polycyclic Aromatic Hydrocarbons with Tetrachloromethane in Two-Component Mixtures
Authors: Wiczk Wieslaw M. , Latowski Tadeusz
Published: February 2015

In the photoreactions of polycyclic aromatic hydrocarbons with tetrachloromethane in binary mixtures of tetrachloromethane with cyclohexane, benzene and acetonitrile, both the quenching of the fluorescence and the photoreactions run through an intermediate stage which is an exciplex of the excited hydrocarbon with tetrachloromethane. Abnormal quantum yields of the hydrocarbon decrease are interpreted in terms of the appearance of a new reaction channel via a triplex consisting of the excited hydrocarbon, solvent and tetrachloromethane. The photoreaction is quenched by diphenylpicrylhydrazyl, thus suggesting the radical nature of the chemical transformations. A kinetic scheme is suggested for the photophysical and photochemical processes describing the observed phenomena.
Notizen: The Effect of Spin-½ Dipolar Coupling on the 2H Quadrupolar Echo
Authors: Gruwel Marco L. H.
Published: February 2015

The effects of dipolar coupling between a deuteron and a spin-½ nucleus on the deuterium quadrupolar echo is calculated. Due to the dipolar coupling the quadrupolar echo amplitude is shown to decay to 1/2 times its initial value for t →∞
Phase Transitions in CsSnCl3 and CsPbBr3 An NMR and NQR Study
Authors: Sharma Surendra , Weiden Norbert , Weiss Alarich
Published: February 2015

The phase transitions in CsSnCl3 and CsPbBr3 have been studied by X-ray powder diffraction, by 81Br-NQR and by 'H-, 119Sn-, and 113Cs-NMR. At room temperature in air CsSnCl3 forms a hydrate which can be dehydrated to the monoclinic phase II of CsSnCl3. The high temperature phase I has the Perovskite structure, as the X-ray and NMR experiments show. The three phases of CsPbBr3, known from literature, have been corroborated. The results are discussed in the framework of the group ABX3, A = alkalimetal ion, B = IV main group ion, and X = Halogen ion
Monte Carlo Simulations with an Improved Potential Function for Cu(II)-Water Including Neighbour Ligand Corrections
Authors: Rode Bernd M. , Islam Saiful M.
Published: February 2015

Monte Carlo simulations for a Cu2+ ion in infinitely dilute aqueous solution were performed on the basis of a simple pair potential function leading to a first-shell coordination number of 8, in contrast to experimental data. A simple method was introduced therefore, which allows the direct construction of a pair potential containing the most relevant 3-body interactions by means of a correction for the nearest neighbour ligands in the ion's first hydration shell. This procedure leads to much improved results, without significant increase in computational effort during potential construction and simulation
A Finite-Field Calculation of the Dipole Flvperpolarizability of Ammonia
Authors: Maroulis George
Published: February 2015

The first (ß) and second (y) electric dipole hyperpolarizabilities are calculated for the ground state of ammonia. All independent components of ßxßy and yxßyö are obtained from the energies of the molecule perturbed by a homogeneous electric field. The values of yxxxx, yxxxz, yxxzz and yzzzz are 1232, -106, 1077 and 4319 e4 a4
0Eh
-3 respectively
Localized NMR Spectroscopy with a 1.5 T Whole- Body Imager Using CODEX
Authors: Jung Wulf-Ingo , Lutz Otto , Pfeffer Markus
Published: February 2015

With a whole-body NMR imager working at 1.5 T localized 1H and 31P spectra were obtained using the CODEX sequence. Examples are presented: With ethanol 'H spectra the resolution, stability, and sensitivity are documented. Human in vivo investigations of the yellow bone marrow of (13 mm)3 volume elements show well resolved spectra with a good signal-to-noise ratio. An example for 31P spectroscopy is also given
Electronic and Geometrical Structure of Se5, Se6, Se7, and Se8
Authors: Becker J. , Rademann K. , Hensel F.
Published: February 2015

The vacuum-UV-photoelectron spectra of Se2, Se5, Se6, Se7, and Se8 have been recorded at a photon energy of h ν= 10.0 eV. The isolated molecules are examined in a supersonic molecular beam employing a new photoelectron-photoion coincidence technique. The structure of the photoelectron spectra of selenium molecules with even and odd numbers of atoms differs in a characteristic manner. While the spectra of Se6 and Se8 show one single broad band, three separated bands with different intensities are observed for Se5 and two for Se7. The spectra are compared to molecular orbital energy calculations based on theoretically supposed geometries. The comparison indicates that Se6 and Se8 have Dnd-symmetrical ring structures, whereas Se5 and Se7 are C1h-symmetrical rings
Structural Characterization of Nickel Oxide
Authors: Massarotti V. , Capsoni D. , Berbenni V. , Riccardi R. , Marini A. , Antolini E.
Published: February 2015

It is known from the literature that a slight distortion of the ideal cubic cell is present in the NiO structure. This work shows that such a distortion can be accurately evaluated by means of a refinement of the structural and profile parameters of X-ray powder diffraction data. Moreover, since only small amounts of products are sometimes at disposal to perform structural characterizations, it was thought useful to extend the refinement procedure to X-ray data collected on NiO samples of much lower mass (15-60 mg) than those usually utilized in X-ray diffractometric studies. The results obtained show that reliable structural parameters can be obtained from low mass samples too
I4N Quadrupole Coupling in the Rotational Spectra of 2,2,2-Trifiuoroethylamine. Isopropylamine, and Aminoethanole
Authors: Keussen Ch. , Dreizler H.
Published: February 2015

We utilized the high resolution of microwave Fourier transform spectroscopy to investigate the 14N-hyperfine structure of trans-2,2,2-trifluoroethylamine, CF3CH2NH2, trans-isopropylamine, CH3CHNH2CH3, and aminoethanole, HOCH2CH2NH2, and the amino deuterated isotopomers trifluoroethylamine-d2 and isopropylamine-d2. The complete coupling tensor of trifluoroethylamine could be determined. We found that the fluorine atoms have a distinct effect on the nitrogen electronic surrounding of the named molecule, presumably through a hydrogen bridge bond between two of these atoms and the amino protons. For isopropylamine and aminoethanole wrong values of the coupling constants known in the literature could be corrected
The Microwave Spectrum of15N-Difluoroacetonitrile: Electric Dipole Moment and Partial r0-Structure
Authors: Ohle Bettina , Mäder Heinrich , Guarnieri Antonio
Published: February 2015

The rotational spectrum of15N-difluoroacetonitrile has been investigated in the frequency range from 8 to 18 GHz. From the measured lines with J up to 20, rotational constants and quartic centrifugal distortion constants have been determined. For some lines the Stark effect has been examined, yielding the components of the electric dipole moment along the a- and c-principal axes of inertia. The obtained rotational constants were also used together with the rotational constants of the normal isotopomer to derive a partial restructure of the molecule
Excimer Parameters of Anisole
Authors: Polacka Bogumila , Polacki Zenon
Published: February 2015

Fluorescence spectra of anisole at various concentrations and temperatures were measured. Using a standard, the molecular quantum efficiency was obtained. Ours and literature data were analysed to determine the rate parameters and other properties of the anisole excimer-monomer system.
Wave Function Properties and Shifted Energy Levels of Bound States in a Plasma
Authors: Lehmann H. , Ebeling W.
Published: February 2015

On the basis of earlier work we show a simple way to estimate the properties of bound states in a plasma. The Bethe-Salpeter equation is approximated by an effective Schrodinger equation. The energy eigenvalues are found via a variation procedure. The treatment is applicated to helium-like bound states and excited hydrogen-like states. The effect of the new energy eigenvalues on the plasma composition is discussed for the symmetrical electron-positron plasma.
Vibrational Band Origins of the Fundamentals v12 and v5 of Furazan from Laser/Microwave Double Resonance
Authors: Stiefvater Otto L.
Published: February 2015

Information from rotational spectroscopy has been utilised for the interpretation of experimental results from laser/microwave double resonance (LMDR) experiments on furazan. The band origins v0 for the fundamental vibrations v12 and v5 have been deduced from these experiments as v0
12 = 952.611 (2) cm -1 and = 1005.353(2] cm-1

General implications of the approach and of the LMDR technique are considered.
Structural Study of a Decagonal Al75Fe15Ni10 Alloy by Anomalous X-ray Scattering (AXS) Method
Authors: Matsubara E. , Waseda Y. , Tsai A. P. , Inoue A. , Masumoto T.
Published: February 2015

A structural study of an as-quenched decagonal Al75Fe15Ni10 alloy has been carried out by anomalous x-ray scattering (AXS) as well as ordinary x-ray diffraction. The environmental radial distribution functions (RDFs) for Fe and Ni determined by the AXS measurements turned out to resemble each other and to be similar to the ordinary RDF obtained by ordinary x-ray diffraction. These results clearly show that the Ni and Fe atoms are homogeneously distributed and occupy the same sites in the decagonal structure of Al75Fe15Ni10.
Isomerization of Diphenyl Polyenes
Authors: Kawski A. , Gryczyński Z. , Gryczyński I. , Wiczk W. , Malak H.
Published: February 2015

We describe an unusual temperature dependence of 1,8-diphenyl-1,3,5,7-octatetraene absorption in poly(vinyl alcohol) films. Upon heating above 80 °C, the optical density (in the long wavelength region) of this compound increases rapidly. A sample heated to 150 °C has a nearly twenty times higher optical density than a non-heated sample. This effect is not reversible: Once the sample is heated it retains its absorbance on cooling to room temperature. In our opinion, the effect has its origin in changes of the chromophore molecules from cis to trans conformation at the high temperature. Possible applications of these unique material properties should be improved temperature sensors, optical data storage, non-developed high resolution photography or typing, etc.
Ion-Solvent Interactions of Zinc(II) Salts in Water- Pyridine Mixtures
Authors: Varghese Antony V. , Kalidas C.
Published: February 2015

The ion-solvent interactions involving zinc(II) salts viz. iodate, fluoride and benzoate in waterpyridine mixtures have been investigated by solubility and solvent transport number measurements. The standard Gibbs transfer energies of the salts (Δ Gtº), determined from their saturation solubilities in the solvent mixtures, decrease up to xpy = 0.1 for zinc(II) iodate, but up to Xpy = 0.4 for zinc(II) benzoate, and subsequently increase with the addition of pyridine. For zinc(II) fluoride, however, a continuous increase of ΔGtº with the addition of pyridine is observed. The transfer energy of Zn2 + is negative and that of anions is positive with the former decreasing and the latter increasing continuously with the addition of pyridine. The solvent transport number of pyridine (<Δpy) is positive and passes through a maximum for all the salts in the range xpy = 0.25 to 0.55. These results indicate a heteroselective solvation of the salts with Zn2 + being preferentially solvated by pyridine and the anions by water
1 /N -Energy-Solutions to Relativistic Two-Boson Systems with an Exponential Potential
Authors: Papp E. , Micu C.
Published: February 2015

Closed 1/N-energy-formulae for relativistic two-boson (m1 ≠ m2) systems with a vector exponential potential have been written down to first 1/N-order. Numerical estimates and structural properties are presented
Rotational Excitations and Tunneling of Nonequivalent Methyl Groups in Tetramethylstibonium Iodide as Studied by Nuclear Magnetic Resonance and Inelastic Neutron Scattering
Authors: Burbach Günter , Weiss Alarich
Published: February 2015

Nuclear magnetic resonance (NMR) and inelastic neutron scattering techniques (INS) have been applied to study the rotational motions and methyl group tunneling in tetramethylstibonium iodide, [Sb(CH3)4 ] I, over er a wide temperature range. Parameters describing the [Sb(CH3)4]+ cation tumbling and the methyl group reorientation at high temperatures and quantum mechanical tunneling of the methyl groups at low temperatures were determined. The results for INS and NMR experiments at low temperatures can be explained in terms of two crystallographically inequivalent methyl groups CH3(1) and CH3(2), which were established earlier by the crystal structure determination. In the INS spectra two tunneling lines at 22.0 μeV for CH3(1) and 1.05 μeV for CH3(2) with inelastic intensities in the ratio 3:1 were observed at T = 4 K. The activation energies derived from proton NMR spin-lattice relaxation time measurements for the thermally activated methyl group rotation are 1.50 kJ/mol for CH3(1) and 3.81 kJ/mol for CH3(2). They are in accordance with the activation energies obtained from neutron fixed-window measurements. The activation energy for [Sb(CH3)4]+ cation tumbling is 50.9 kJ/mol as determined from the high temperature spin-lattice relaxation behaviour. Rotational potentials for the methyl groups are derived. For both kinds of inequivalent methyl groups the threefold potential terms dominate; three- and sixfold potential contributions are shifted by 180°
The Rotational Zeeman Effect of Imines II. Cis- and Trans-Ethanimine and Trans-Syn- and Trans-Anti-Propenimine, their g-Tensors, Magnetic Susceptibility Anisotropics, Molecular Electric Quadrupole Moments, 14N Nuclear Quadrupole Coupling Constants, and 14N Spin-Rotation Coupling Constants; a Microwave Spectroscopic Study Combined with Quantum Chemical Calculations
Authors: Krause H. , Sutter D. H.
Published: February 2015

The zero field 14N-hfs-multiplets and the high-field Zeeman-hfs-multiplets of low-J rotational transitions of the title compounds were observed in a flash pyrolysis setup under high-resolution conditions. From the zero-field hfs patterns the 14N spin-rotation coupling constants and the 14N nuclear quadrupole coupling constants were obtained. From the high-field Zeeman-hfs-multiplets, the diagonal elements of the molecular g-tensor and the anisotropies in the diagonal elements of the molecular magnetic susceptibility tensor were determined and were used to derive the diagonal elements of the molecular electric quadrupole moment tensor. INDO calculations and restricted Hartree-Fock self consistent field calculations with a basis of TZVP quality were carried out at the experimental structures and critically compared to the experimental results
The Microwave Spectrum of 1,1-Dichloro-2,2,2-Trifluoroethane
Authors: Merke I. , Grabow J.-U. , Heineking N. , Stahl W.
Published: February 2015

We assigned the microwave spectrum of 1,1-dichloro-2,2,2-trifluoroethane in its vibrational ground state using a pulsed molecular beam microwave Fourier transform (MB-MWFT) spectrometer. For the 35Cl, Cl-isotopomer the rotational constants were found to be A = 2105.7098(38) MHz, B = 1689.8304 (35) MHz, and C = 1135.6955 (23) MHz, the quadrupole coupling constants of the 35Cl-nuclei are χaa = 12.385 (35) MHz and χbb= -42.284(31) MHz. The rotational constants of the 35Cl,37Cl-isotopomer are A = 2071.5469 (33) MHz, B = 1670.7648 (36) MHz, and C = 1117.1755 (24) MHz, the corresponding quadrupole coupling constants are χaa = 17.639 (51) MHz and χbb= -47.670(67) MHz for the 35Cl-nucleus and χaa = 4.701 (54) MHz and χbb= -28.331 (83) MHz for the 37Cl-nucleus
Solvent Effects on the Fluorescence Properties of Methyldihydroquinolinones
Authors: Bakalova Snezhana
Published: February 2015

The absorption and fluorescence spectra and the fluorescence quantum yields of two methyl-2,3- dihydro-4(1H)-quinolinones in various solvents are reported. In some solvents deuteration-induced fluorescence enhancement has been observed. The solvent effects in aprotic solvents are consistent with the general type of solvent interaction. For protic solvents, solute-solvent complexation in the excited state is suggested
A Method for the Calculation of Thermodynamic Functions for the 3 D Model Systems in the Critical Region
Authors: Yukhnovskii I. R. , Kozlovskii M. P. , Pylyuk I. V.
Published: February 2015

A method for the calculation of the thermodynamic functions in the three-dimensional using model near the phase transition is proposed. In the frame of a uniform approach, the critical exponents and the critical amplitudes of the main characteristics of the model (i.e. free energy, enthropy, specific heat, etc.) are obtained as functions of microscopic Hamiltonian parameters.

It is shown that the correct sign and temperature behaviour of the entropy are provided due to the contribution of the long-wave spin moment modes. The short-wave ones are responsible for the values of the critical exponents.
Intermolecular Potential Function for Hydroxylamine Dimer Interactions from ab initio Calculations
Authors: Michopoulos Yanos , Botschwina Peter , Rode Bernd M.
Published: February 2015

The derivation of an intermolecular potential function for the interaction of two hydroxylamine molecules, based on ab initio SCF-ECP calculations is reported. Ab initio values were compared for selected geometries with those obtained from calculations with much larger basis sets, inluding electron correlation effects by the CEPA method. A total 658 energy values were then fitted to an analytic sum of atom-atom isotropic pair potential functions, whose functional form was given a simple electrostatic interpretation. The major difficulties, arising from the relatively low values of the stabilisation energies of the system and the numerous possibilities to form hydrogen bonds, were overcome by a careful selection of sufficient points on the potential hypersurface, introduction of cut-offs and weight factors. The obtained function was seen to be able to give a good reproduction of the interaction energies and proved suitable in a preliminary MC simulation
Modelling of Partial and Total Radial Distribution Functions of Amorphous Ni2B Using Reverse Monte Carlo Simulation
Authors: Pusztai Läszlö
Published: February 2015

The use of Reverse Monte Carlo simulation, a novel method of structural modelling, looks very promising for the case of metallic glasses. In this paper initial results are shown for glassy Ni2B, using experimental radial distribution functions as input information.
Pulsed Neutron Diffraction Studies on Lanthanide(III)Hydration in Aqueous Perchlorate Solutions
Authors: Yamaguchi T. , Wakita H. , Tanaka S. , Misawa M. , Okada I. , Soper A. K. , Howells W. S.
Published: February 2015

Pulsed neutron diffraction measurements are reported on 2 molar aqueous solutions of Pr3 + , Nd3 + , Tb3 + , Dy3 + , Tm3 + , and Yb3+ in D2O at room temperature. The first order difference technique on isomorphous ions is used to derive the metal ion pair correlation functions in these systems. The metal-oxygen and metal-deuterium distances and the hydration numbers are determined. The data indicate that the hydration number changes from ~ 10 for the lighter ions to ~8 for the heavier ones in the series. The water dipole is orientated on the average at an angle of 10 ~ 20 degrees to the metal-oxygen vector; these values are significantly smaller than those found for mono- and di-valent ions. The present results are compared with other results from neutron diffraction with isotope substitution, X-ray diffraction, and extended X-ray absorption fine structure.
Excess Properties of Water-Methanol Mixtures as Studied by MD Simulations
Authors: Pálinkás G. , Bakó I.
Published: February 2015

Molecular dynamics simulations with pair interactions reproduce experimental excess properties of methanol-water mixtures. Water molecules lose, and methanol molecules gain neighbours in the mixtures as compared to the solvents. The water-methanol mixture with 0.25 mole fraction of methanol, resulting in extreme values for different excess properties, is characterized by the highest number of molecules with maximal number of H-bonded neighbours.
A Study of Hydrated Rare Earth Ions
Authors: Hengrasmee Sunantha , Probst Michael M.
Published: February 2015

Hydrated lanthanide(III) ions Ln3 + (H2O)8 with Ln3 + = La3 + to Yb3+ have been studied using ab-initio methods. The binding energy as a function of ion-water distance and position of the ion in the rare earth series is discussed. The calculations are related to recent experimental results elucidating the hydration behaviour of lanthanide(III) ions. Since no S-shape behaviour is found for complex binding energies or metal-oxygen distance, the calculations indicate that observed thermodynamic anomalities should come from hydration number changes due to the different ionic radii within the series.

The non-additivity of the ion-water interactions has been calculated and it is found that its relative importance increases from 26% for La3+ to 32% for Ln3 +
Transition Between Molten-Saltand Solvated-Ion States of Proton Hydrates:Comparative Double-Layerand Electrode-Kinetic Behaviour at Hg and Au Interfaces
Authors: Qian S. Y. , Conway B. E.
Published: February 2015

The question of the structure of the electrical double-layer at electrodes in contact with electrolyte solutions has several aspects in common with the long and short-range structure of electrolyte solutions. Measurements of the capacitance of the double-layer have traditionally provided information on this question for the case of dilute electrolyte solutions.

With proton hydrates from H3O+ through H9O4
+ to 1 M aqueous H+ solution made by stoichiometric addition of water to the acid CF3SO3H, the transition between "molten-salt" (H3O+ CF3SO3 above 307 K) to "dilute-solution" behaviour of the interphasial double-layer at Hg and Au electrodes can be investigated. The H3O+ CF3SO3 is a highly conducting molten salt above 307 K. The results indicate that the double-layer capacitance at potentials negative to the RHE, both at Hg and Au, in the H3O+ molten salt has values surprisingly similar to that in 1 M aq. H+ solution. Intermediate states of hydration of the proton (H5O2
+, H7O3, H9O4
+) have higher values, especially at Au. However, the capacitance behaviour is quite different from that observed in high-temperature, alkali-metal molten salts at Pb.

Models are proposed for the structures of the double-layers in these proton-hydrate systems, and the problem of accounting for a "normal" value (ca. 18 μF cm-2) of capacitance at Hg in the H3O+ melt is examined by means of some model calculations.

Comparative electrode-kinetic measurements on proton discharge add further information on the behaviour of the proton hydrates.