bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR Investigation of Order Fluctuations, Self-Diffusion and Rotational Motions in the Nematic Liquid Crystal MBBA by T1-Relaxation Spectroscopy
Authors: Graf V. , Noack F. , Stohrer M. 
Published: February 2015

Abstract
We report on measurements of the proton spin T1 relaxation dispersion at various temperatures in the nematic phase of the liquid crystal MBBA in the Larmor frequency range from 2 kHz to 270 MHz, which exceeds previous studies by more than 3 orders of magnitude. The new results cannot be interpreted in terms of either order fluctuations or self-diffusion as recently proposed by Doane et al.1 and Blinc et al.2, respectively. Instead, the dispersion and its temperature dependence indicate the significance of at least three relaxation mechanisms, namely order fluctuations (OF), self-diffusion (SD) and rotation of the molecular ellipsoids about the short axis (R). The combined OF-SD-R model presented in this work allows a quantitative analysis of the experimental findings! The correlation times and activation energies of the three molecular reorientations evaluated from the T1 dispersion by means of a computer optimization procedure are in essential agreement with data provided by other spectroscopic methods [light scattering, tracer technique, dielectric relaxation], but differ from former NMR conclusions.
Systematic Patterns in the E1 Decays in 21Ne and 23Na: A Means of Identifying High Spin States?
Authors: Pilt A. A. 
Published: February 2015

Abstract
The El decays from members of the lowest Kπ= 1/2- bands in 21Ne and 23Na are shown to exhibit remarkable, but dissimilar, patterns, which can be reproduced with a simple two-parameter expression. This may have useful application in identifying high-spin members of the Kπ= 1/2- and 3/2+ bands in both nuclei.
Population Density Measurements in a Partially Ionized Freejet Expansion Flow
Authors: Kimura Akira , Nishida Michio 
Published: February 2015

Abstract
Population densities of the 4p and 5p levels of argon atoms were measured along a freejet centerline of partially ionized argon in a low density plasma wind tunnel. The measured axial distribution of the 4p[3/2] level population has been compared with a theoretical prediction using a modified Thomson's formula for the excitation cross sections.
Generalization of the Moment Method of Maxwell-Grad for Multi-Temperature Gas Mixtures and Plasmas
Authors: Weinert Ulrich , Suchy Kurt 
Published: February 2015

Abstract
A coupled system of balance equations is derived for the coefficients of orthogonal expansions of the velocity distribution functions. The orthogonal functions are not specified, but the initial func­ tions must be local Maxwellians with different temperatures for different species of particles. Closed expressions for the matrix elements of the non-linearized Boltzmann operator are given, whose dominant terms are determined and compared.
Die physikalischen Grundlagen der Uran235-Anreichcrung nach dem Trenndusenverfahren
Authors: Becker E. W. , Bier W. , Bley P. , Ehrfeld U. , Ehrfeld W. , Eisenbeiß G. , Rosenbaum F.-J. , Schmid E. 
Published: February 2015

Abstract
In the separation nozzle process for enrichment of U-235 the kinetic energy of the jet is con­ centrated in the heavy fraction of the H2/UF6 mixture. Flow measurements with free molecular probes and separation experiments have shown that this energy can be utilized in a so-called double deflection nozzle to increase significantly the overall isotope separation effect.
On the Absorption Spectrum of Isoquinoline and 3-Mcthylisoquinoline in Tetrahydrofuran and n-Paraffin
Authors: Kawski A. , Gryczyǹski I. , Kojro Z. , Janic̀ I. 
Published: February 2015

Abstract
The quasilinear absorption spectra of isoquinoline and 3-methylisoquinoline have been studied in tetrahydrofuran and n-paraffin solvents at 77 °K. An analysis of the vibrational structure in the first electronic excited singlet state (S1 is given. Different multiplicities of the absorption spectra have been studied and explained.
Spektren und Abklingprozessc der Mn(II)-Lumineszenz in Alkalichloriden; Untersuchung ihrer Konzentrationsabhangigkeit in MnCl2/LiCl / Spectra and Decay Processes of the Mn(II)-Luminescence in Alkali Chlorides; Investigation into their Dependence on Concentration in MnCl2LiCl
Authors: Oelkrug D. , Bina E. 
Published: February 2015

Abstract
Luminescence emission spectra, excitation spectra and decay curves of manganese (II) in alka­ line chloride host lattices were measured at room temperature and 77 K. In most samples the decay curves deviate strongly from an exponential function. Concentration and temperature dependence of the results and a comparison with the homogeneous phases of manganese (II) compounds leads to the following conclusion: In LiCl the statistical incorporation of Mn(II) predominates strongly; an interaction dependent on concentration between Mn (II) -ions and cationic lattice defects could be detected. In NaCl, isolated and linked MnCl6-octahedra have to be considered also at very low Mn (II) -concentrations. In KCl, pairs and bigger aggregates of linked octahedra occur much more frequently than the isolated MnCl6 units. In RbCl a uniform new phase of rubidiumchloro-manganate with linked MnCl6-octahedra is formed. The situation in CsCl is quite similar to that in RbCl, but there exists an additional metastable phase with MnCl4-tetrahedra.
A Simple Model for Liquid or Amorphous Metals
Authors: Blétry J. 
Published: February 2015

Abstract
The structure of liquid or amorphous metals is described by means of an harmonic approxima­ tion where atoms vibrate around the equilibrium positions of a random hard sphere network. This model depends on three parameters, of which the only adjustable one is the atomic vibration frequency, which is shown to be proportional to the Debye frequency of the corresponding crystalline phase. The atomic diameter is deduced from the position of the structure factor first peak and turns out to be equal to the Goldschmidt diameter. The packing fraction temperature variations are at­ tributed to presence of a variable number of randomly distributed atomic holes and deduced from density measurements. Good agreement with experimental structure factor determinations is found for a wide variety of liquid metals.
Phasentrennung als Folge der Konkurrenz zwischen „statistischcr“ und „chemischer“ Vermischung / Interpretation of Phase Separation as the Result of a Competition between "Statistical'' and "Chemical" Mixing
Authors: Becker Friedrich , Kiefer Michael , Rhensius Peter , Schäfer Hans-Dieter 
Published: February 2015

Abstract
The fact that common thermodynamic conditions are valid for all known types of critical phases (liquid-liquid, liquid-gas, and "gas-gas") suggests that a common principle for the interpretation of material phase instability from a molecular point of view must exist. In this paper we show that the principle of competition between "statistical mixing" (i. e. random mixing) and "chemical mixing" (i. e. mixing effected under the influence of chemical interactions) can give this common inter­ pretation. If the equilibrium states resulting from both types of mixing are sufficiently different, phase separation occurs. We refer to our earlier papers (since 1972) in which we have applied this principle to describe liquid-liquid phase equilibria by "chemical" models, using the equilibrium constants of exchange equilibria between nearest-neighbour complexes as a measure of "chemical" mixing. In this paper we show that the well-known reduced gas-liquid coexistence curve, T/Tc =f(q/qc), can accurately be fitted by a very simple "mixture" model of molecules A with "vacan­ cies", provided that the contributions of both statistical and chemical mixing are incorporated into the formula for GE. From a discussion of the application to "gas-gas" phase equilibria in the hyper­ critical region it results that the weight factor r, by which the contribution of statistical mixing enters into GE, must depend on the density of the gas mixture. Phase separation can only occur if, by increasing pressure, the contributions to GE of statistical and chemical mixing have reached the same order of magnitude. From an attempt to apply the same principle to solid-liquid equilibria it is shown under which external conditions a critical point for this type of phase transition can be expected.
The Microwave Spectrum of Silylisothiocyanate, SiH3NCS
Authors: Dössel K.-F. , Robiette A. G. 
Published: February 2015

Abstract
The J → J+1 transitions (J = 8, 9, 10 and 11) in the microwave spectrum of SiH3NCS have been assigned for the vibrational ground state and for the states ν10 = 1, 2 and 3. The results extend earlier work, giving more precise values for several of the molecular constants. Resonances in the excited vibrational states have been analysed: from these, values are deduced for the anharmonicity constant g10,10 and the vibrational interval ν10=1→2. The spectra of molecules isotopically substituted with 29Si, 30Si and 34S have been reassigned, and the resulting rs coordinates are in excellent agreement with bond lengths determined by electron diffraction.
Dipole Moments and Absorption Spectra of 2-Pyridyl-Phenyl Sulphide and 2-Pyridyl-Phenyl Sulphone
Authors: Galasso Vinicio , Pappalardo Giuseppe C. , Scarlata Giuseppe 
Published: February 2015

Abstract
The electric dipole moments in benzene solution have been measured for the title compounds and analysed in terms of the conformations of these molecules in solution. The origin of the electronic absorptions have been interpreted by means of a theoretical approach (CNDO/S-CI) and, to­ gether with the S02 stretching vibrations, have been com­ pared with the corresponding spectral features observed for the analogous related diphenyl and di-2-pyridyl compounds.
Nuclear Magnetic Relaxation in the Presence of Quadrupole Nuclei
Authors: Kimmich Rainer 
Published: February 2015

Abstract
Nuclear magnetic relaxation formulae are given for dipolar nuclei interacting with quadrupolar nuclei. The following cases are distinguished: High-and low-field case with respect to the quadrupole energy levels and, on the other hand, quasi rigid lattices and tumbling lattices with respect to molecular motions.
As examples of these cases, the proton T1-dispersion of Polyvinylchloride (quasi rigid lattice) and of protein solutions (tumbling lattice) are discussed and compared with theory. It is shown that the influence of the interaction with quadrupole nuclei is normally not negligible.
PVC shows a quadrupolar dip below room temperature as an especially remarkable consequence of the interaction with chlorine. An oscillator model is discussed in order to explain the molecular motion at low temperatures.
Proteins contain imino-groups acting as relaxation centers and mediating the contact to the aqueous solvent via hydrogen bonds. These relaxation centers can explain the low absolute values of the longitudinal relaxation times in protein solutions. Furthermore, several effects in such systems, reported previously, can easily be interpreted on the basis of the presented formalism.
Dissociation and Charge Transfer of CO2
1+ and CO2
2+ Ions in Collisions with Neutral Atoms and Molecules
Authors: Müller A. , Salzborn E. 
Published: February 2015

Abstract
Cross sections for single electron capture by CO2
2+ ions as well as total collision cross sections σi,tot (i=1, 2) for CO2
1+ and CO2
2+ ions in He, Ne, Ar, Kr, Xe, H2, O2, N2, CH4 and CO2 gases have been measured at 10 keV impact energy. σ2,1 varies between 4.5·10-17cm2 for the He and 1.8·10·15cm2 for the CO, target. On the average, σ2,1,tot is 1.6 times larger than σ1,tot and shows a nearly linear dependence on the gaskinetic hard sphere cross section of the target particle. The largest observed value of σ2,tot is 9.4·10-15cm2 for the CO2 target.
Collisional Depolarization of Fluorescence in the Impact and Quasistatic Limit
Authors: Behmenburg W. , Schüller F. 
Published: February 2015

Abstract
Collisional Depolarization of fluorescence radiation has been treated by considering the impact and the quasistatic limit of the general theory of redistribution. The result shows that a variation of the degree of polarization within the fluorescence spectrum is to be expected.
Debye Waller Factors of fee Metals by the Modified Angular Force Model
Authors: Kharoo Hira Lai , Gupta O. P. , Hemkar M. P. 
Published: February 2015

Abstract
A modified form of the non-central force model which takes account of the electron-ion inter­ action term of the Kreb's model in the Clark, Gazis and Wallis type angular forces is considered to calculate the Debye-Waller exponents at different temperatures for five fee metals: copper, silver, gold, aluminium and nickel. The results are compared with the available x-ray measurements in terms of the temperature parameter Y of the Debye-Waller factor, the Debye characteristic temperature ΘM and the mean square displacement of the atoms. The theoretical results are found to be in reasonably satisfactory agreement with the experimental values.
Photodetachment bei einigen zweiatomigen negativen Hydridionen: BeH–, MgH-, CaH-, ZnH-, PH-, AsH- / Photodetachment of Some Diatomic Negative Hydride Ions BeH-, MgH-, CaH-, ZnH-, PH-, AsH-
Authors: Rackwitz R. , Feldmann D. , Kaiser H. J. , Heinicke E. 
Published: February 2015

Abstract
The cross sections have been measured in a photon energy range between 0.5 eV and 3 eV. From threshold energies the electron affinities of the molecules have been determined.
A Molecular Dynamics Study of Aqueous Solutions VI. Remarks on the Hydration Numbers of Alkali and Halide Ions
Authors: Bopp P. , Heinzinger K. , Jancsò G. 
Published: February 2015

Abstract
It is proposed to define the hydration number derived from molecular dynamics simulations by the volume integral over the ion-water radial pair distribution function up to the first minimum. In order to compare such numbers with experimental results, the literature on the hydration numbers of alkali and halide ions is examined. Only the hydration numbers derived from x-ray and neutron diffraction studies are defined in a similar way and can be compared with molecular dynamics results. Considering the difficulties in deducing hydration numbers even from these two methods, the agreement might be called fair.
On Nonlocal Constitutive Relations, Continued Fraction Expansion for the Wave Vector Dependent Diffusion Coefficient
Authors: Hess Siegfried 
Published: February 2015

Abstract
Nonlocal constitutive relations which involve wave vector dependent transport coefficients can be derived from the Boltzmann equation. Diffusion of a Lorentzian gas is treated as an illustrative example. Transport-relaxation equations obtained from the Boltzmann equation with the help of the moment method lead to a continued fraction expansion for the wave vector dependent diffusion coefficient D(k). Rapidly converging upper and lower bounds on D(k)/D(0) are found which are meaningful for all values of lk where l is a mean free path and k is the magnitude of the wave vektor k. Also some remarks on a frequency and wave vector dependent diffusion coefficient are made.
Local Excitation as Transport Phase Transition in Phonon Systems
Authors: Kaiser Fr. 
Published: February 2015

Abstract
The Peierls-Boltzmann transport equation for phonons, which was re-formulated and modified in a previous paper, is extended to be applicable to arbitrary interactions and phonon processes. As a rule, it turns out that only two types of steady state solutions are possible: hysteresis and threshold. These two solutions reveal the possibility of “transport phase transitions”, i. e. a transition from the “thermodynamic” branch to a “nonthermodynamic” one via a cumulative excitation. It is shown that both the threshold and the hysteresis situation exhibit pronounced analogies to phase transi­tions in thermal equilibrium. The dependence of the steady states from the relevant parameters is discussed.
EPR and ENDOR of cubic ZnS: Mn2+
Authors: Beer R. de , Biesboer F. , Veen G. van 
Published: February 2015

Abstract
The spin Hamiltonian parameters of 55Mn2+ in cubic ZnS have been determined by means of EPR and central-ion ENDOR, using Ka-band (35 GHz) microwaves. For the first time a value for the spherical electric quadrupole interaction of Mn2+ incorporated in a single crystal has been found. Also the ligand hyperfine interaction and the electric quadrupole interaction of the twelve Zn67 nuclei nearest to Mn2+ have been determined by means of ligand ENDOR.
Die Temperaturabhangigkeit der elektronischen Kenngrofien des eigenleitenden Siliciums
Authors: Wasserrab Th. 
Published: February 2015

Abstract
From phenomenological equations for the electric resistance and the electron and hole mobilities, the intrinsic carrier concentration is calculated (ni = 1.02 · 1010 cm-3 at T = 300 K) and its temperature dependence is derived. Correlation with a well-known quantum-statistical equation delivers the temperature dependence of the density-of-states effective masses.
On the Conformational Analysis of N,N-Dimethyloxamide
Authors: Veken B. J. van der , Desseyn H. O. , Herman M. A. 
Published: February 2015

Abstract
The results of an energy optimization, using CNDO/2, with respect to two internal dihedral angles in N,N-dimethyloxamide are reported. The lowest minimum is found for a planar dimethylamide function, twisted around the C -C bond over an angle of 80.5 degrees with respect to the other amide function. Some calculated properties are compared with experimental data.
EEHMO-Rechnungen zur Valenzisomerisierung zwischen benzenoiden und o-chinoiden Systemen
Authors: Kolshorn Heinz , Meier Herbert 
Published: February 2015

Abstract
A special aspect of benzocyclobutenes and the heteroanalogous systems is the valence isomerization. which leads by ring opening to o-quinoidal structures. The energy balance of such [2π + 2σ]- reactions and the reverse [2π +2π] -cyclo-additions in the ground state S0 and in the first excited singlet state S1 are discussed. The EHT-calculation performed are based on a partial geometry optimation.
Proton Medium Effects Utilising Ferrocene Redox Couple as Reference in Propylene Glycol- Water, Methanol-Propylene Glycol and Methanol-Water Mixtures
Authors: Kalidas C. , Sivaprasad P. , Venkatram U. V. 
Published: February 2015

Abstract
Utilising the ferrocene reference method, proton medium effects (log mγ H+) were determined in methanol-water, pro­ pylene glycol-water and methanol-propylene glycol mixtures of varying composition. On the basis of the ferrocene meth od, it was shown that all methanol-water, propylene glycol-water and methanol-propylene glycol mixtures including the pure solvents are more basic than water and these results were explained in terms of the structural theory of ion sol­ vation proposed by Feakins and coworkers. Further, it was shown that methanol is slightly more basic than propylene glycol which is in agreement with the conclusions arrived from earlier EMF measurements.
Absorption Measurements of the Principle Series Lines of Cs Broadened by Xe
Authors: Lorenzen J. , Niemax K. 
Published: February 2015

Abstract
The absorption coefficients of the statistical wings of the Cs principal series lines 6 2S1/2 - n 2P3/2 (6 ≦ n ≦ 10) and 6 2S1/2 - n 2P1/2 (6 ≦ n ≦ 9) perturbed by Xe have been measured quantitatively The results are compared with quasistatic line wings calculated from the interatomic Cs -Xe potentials of Baylis 1 and Pascale and Vandeplanque 2. In the far wings of the higher lines of the series indications of many-body interaction were found. Furthermore the behaviour of the shift of all principal series lines up to the 23rd member was investigated in the density region between 1.63 X 1018 and 1.9 X 1019 Xe atoms per cm-3.
The Micro wave Spectrum of Bromoacetylene ; rs-Structure , Dipole Moment, Quadrupole Coupling Constants and Excited Vibration States
Authors: Jones H. , Sheridan J. , Stiefvater O. L. 
Published: February 2015

Abstract
The microwave spectrum of bromoacetylene has been investigated in the frequency range from 7 GHz to 35 GHz. From Stark effect measurements the dipole moment has been determined as μ = 0.23 + 0.01 D, and the restructure has been derived in four independent ways from twelve isotopic species: C - H = 1.0553 Å, C ≡ C = 1.2038 Å, C - Br = 1.7913 Å (internal consistency better than ± 0.0003 Å). Quadrupole coupling constants have been determined for eleven isotopic forms and are e q Q = 541.47 MHz and 648.00 MHz for HCCBr81 and HCCBr79, respectively.
Rotation spectra have also been observed for excited states of the three lowest normal modes and for several isotopic forms. For the Br81 (Br79) species the rotation-vibration coefficients are α5 = -10.98 (-11.02) MHz, α4 = -1.57 (- 1.61) MHz and α3 = + 12.88 (+ 13.40) MHz. For the bending vibrations, ν5 and ν4 , l-type doubling constants are obtained as ql5 = 4.14 (4.17) MHz and ql4 = 2.6 MHz. Analysis of the Fermi resonance between the first excited state of ν3 and the l = 0 component of the second excited state of ν5 gives the mixing ratio of these two states as a/b = 1.45 (1.51) and the interaction energy as W3,5 = 1.313 (1.181) δ3,5 for the Br81 (Br79) species. With an approximate value of δ3,5 ≌ 25 cm-1, the cubic force constant is obtained as κ3,55 ≌ 44 cm-1.
The results are discussed in relation to the molecular properties of other halogen acetylenes and halogen cyanides.
Notizen: Bestimmung des Helixdrehsinnes cholesterischer Phasen mit der Grandjean-Cano-Methode / Determination of the Helical Sense of Cholesteric Liquid Crystals Using the Grandjean-Cano Method
Authors: Heppke G. , Oestreicher F. 
Published: February 2015

Abstract
A simple way of determining the helix screw sense of a cholesteric phase using the Grandjean-Cano method is described. The helix pitch as well as its sense is investigated for ten cholesteric phases, induced by mesogenic chiral com­pounds in the nematic isomere mixture of 4-methoxy-4′-n-butylazoxybenzene (Nematic Phase 4, Merck). For the chiral compounds with nematic-like molecular structure it is found that the screw sense alternates with the number of bonds between the chiral centre and the ring system.
Quadrupole Hyperfine Structure and Splitting of Δ-Levels in the Microwave Spectra of KOH,RbOH and CsOH in the 100 GHz Region
Authors: Kuijpers P. , Törring T. , Dymanus A. 
Published: February 2015

Abstract
Hyperfine structure of rotational transitions of KOH, RbOH and CsOH in various υ2-and l-states has been carefully measured in the 100 GHz range. From the observed splittings and broadenings information about quadrupole coupling constant (eqQ) of the K nucleus in KOH and about the spacing (EΔ - EΣ) between Σ and Δ levels in the vibrational spectrum of KOH, RbOH and CsOH has been derived. The measured value of the eqQ of KOH is close to that of KF. The separation between Σ and Δ levels is found to be rather similar for the group of the alkali hydroxides in­ creasing gradually when progressing from LiOH to CsOH.