bluuebunny/crossref_metadata_2025 huggingface dataset:
Schwingungsspektren der Schwefelringe S8, 34S8, S12 und S12 · CS2 sowie thermodynamische Funktionen der Moleküle Sn (n = 2 — 12) / Vibrational Spectra of the Sulfur Rings S8, 34S8, S12 and S12 · CS2 and Thermodynamic Functions of the Molecules Sn (n = 2…12)
Authors: Steudel Ralf , Mäusle Hans-Joachim
Published: February 2015

Raman spectra of S8, 34S8, S12, and S12 · CS2 are reported and force constants have been calculated for S8 and S12 using a modified Urey-Bradley force field. The fundamental vibrations and molecular geometries of S8 and S12 have been used for the calculation of thermodynamic functions. The standard entropies, S0
T, as well as the molar heat capacities, Cp, of sulfur species Sn are shown to depend linearly on the molecular size, n, as follows (in J · mole-1 · K-1):

S0
298 = 35.16n + 147.0, Cp(298 K) = 21.00 n - 11.7.

By interpolation entropies for S9, S10 and S11 have been obtained, and these data are used to show that the concentrations of sulfur rings larger than S8 in sulfur vapor must be negligibly small.
UPS Study of [2,2] (2,5)Furanophane and [2,2] (2,5)Thiophenophane Evidence Regarding the Importance of Through Bond and Through Space Interactions
Authors: Bernardi Fernando , Bottoni Andrea , Colonna Francesco Paolo , Distefano Giuseppe , Folli Ugo , Vivarelli Piero
Published: February 2015

The ultraviolet photoelectron spectra of [2,2](2,5)furanophane (FUPH) and [2,2](2,5)thiophenophane (THPH) have been analyzed on the basis of a perturbational molecular orbital analysis, by comparison with CNDO/2 computations and by correlating them with the spectra of related molecules. Through space and through bond interactions between the two heteroaromatic rings are shown to be important in determining the ordering of the outermost MO’s in this class of compounds.
Transmission Electron Diffraction Intensities from Real Organic Crystals: Thin Plate Microcrystals of Paraffinic Compounds
Authors: Dorset Douglas L.
Published: February 2015

Solvent-grown microcrystals of long polymethylene compounds packing in the O⊥ methylene subcell are found to have some of the defect structures seen for crystalline polyethylene. Crystals composed either of rectangular layers or of oblique layers both exhibit the growth around a screw dislocation characterized earlier by other workers. In addition, rectangular layer crystals of orthorhombic n-hexatriacontane give evidence of intralamellar edge dislocations. When rectangular layer crystals of cetyl palmitate are grown from hot ethanol, the same surface corrugations are found as seen earlier for polyethylene and orthorhombic paraffins. Oblique layer crystals have not demonstrated these latter two defect structures. All crystals show evidence of appreciable bending.

As was found to be true for rectangular layers of n-paraffins, bending has some influence on the electron diffraction intensities from an oblique layer. Another important factor is a perturbation due to defects along long chain axes which disrupts the ordered packing of polar regions, and causes incoherent scatter from these regions. In addition, observed screw dislocations give a nonuniform end plane, causing isolation of layers from one another. Diffraction models accounting for bending or isolation of chain layers in an oblique layer both explain the observed near invariance of certain intensities which are due to the coherent scattering from the line grating formed by rows of carbon atoms in the tilted chain aggregate. Forbidden reflections predicted by a bending model are less important than those anticipated by the multiple scattering from a laminated layer model. As these forbidden reflections are mostly identified for multilayer crystals and since crystal structure analysis indicates most of the long chain in a oblique monolayer to be diffracting coherently, the concentration of Reneker-type defects in the centers of chains is probably not great enough to isolate small chain length laminae within a monolayer.
Contributions to the Theory of Mass Action Kinetics
Authors: Willamowski Klaus-Dieter
Published: February 2015

Second order mass action kinetics provide the simplest models of nonlinear reaction systems. Some of their dynamic properties, viz., location, number, and stability pattern of their critical points, will be analyzed. The occurrence of periodic and chaotic solutions of these systems is discussed.
Passages in Lecithin-Water Systems
Authors: Harbich W. , Servuss R. M. , Helfrich W.
Published: February 2015

Large numbers of tunnel-like structures apparently connecting neighbouring bilayers were found in phase-contrast microscopy of certain preparations of egg lecithin in water. These passages either cause a pairing of the bilayers or form threedimensional lattices. They appear to originate while the lecithin swells in water. Some theoretical aspects of passage formation in fluid bilayers is shown to be 4πx̅, x̅ being the elastic modulus of Gaussian curvature.
Optical Gain and Saturation Considerations of Organic Dyes
Authors: Heudorfer W. , Marowsky G. , Tittel F. K .
Published: February 2015

A theoretical analysis of optical gain and saturation of organic dye lasers is presented. An analysis based on a solution o f the laser rate equations establishes a convenient method of optical gain measurement by internal fluorescence probing for low-gain system s, such as vapors of organic dyes. The concomitant limitations of high-gain system s (e.g. organic dyes in liquid solutions) of small-signal gain due to amplified spontaneous emission (ASE) and problems associated with gain saturation at high signal inputs are discussed in detail.
13C- and 1H-ENDOR Studies of a Phenoxyl Type Radical
Authors: Lubitz W. , Broser W. , Kirste B. , Kurreck H. , Schubert K .
Published: February 2015

13C- and 1H-ENDOR studies on a phenoxyl type radical in fluid solution are reported. The 13C-ENDOR resonance lines are comparable with those of the protons concerning amplitude, linewidth, and optimum experimental conditions. These findings are in contrast to previous ENDOR experiments on other 13C-labelled systems and can be explained by assuming similar hfs anisotropies for carbon-13 and protons in this radical. From saturation measurements the re­laxation parameters were determined. The hyperfine couplings are discussed in terms of McLachlan and INDO calculations. For the first time natural abundance 13C-ENDOR measurements have been successful.
Beitrag zur Berechnung der strahlenden Rekombinationswahrscheinlichkeit B von eigenleitendem Silicium / Contribution to the Calculation of the Radiative Recombination Probability B in Intrinsic Silicon
Authors: Wasserrab Th.
Published: February 2015

Quantitative calculations of Varshni, using the theory of radiative recombination of van Roosbroeck and Shock- ley yielded a slight increase of the recombination probabi­lity B with temperture T. Measurement of Schlangenotto et al demonstrated in contrast a strong decrease of B with T. It is pointed out, that this discrepancy is only a conse­quence of using approximative ni values (intrinsic carrier concentration) by Varshni. Introduction of new, corrected data of ni yields now a remarcable agreement between calculation and measurement.
Cross Section Ratios for the Electron Impact Production of Singly and Multiply Ionized Rare Gas Ions
Authors: Egger F. , Mark T. D.
Published: February 2015

Electron impact ionization of He, Ne, Ar, Kr and Xe has been studied with a double focussing mass spectrometer Varian MAT CH5. Ratios of various multiple ionization cross sections with respect to single ionization cross sections for He, Ne, Ar, Kr and Xe at electron energies of 50, 100 and 150eV are given. These cross section ratios are com­pared with previous determinations.
Eine Modellbetrachtung zur Triplettkinetik von Anthracen/Tetracen Kristallen/A Model consideration of the Triplet Kinetics in Anthracene/Tetracene Crystals
Authors: Wolff H. , Schmillen A.
Published: February 2015

Earlier measurements on anthracene/tetracene crystals are now interpreted with a simplified new model of the triplet kinetics. One result is a threefold exponential decay of the delayed fluorescence of both host and guest. The lowest decay rate as function o f the guest concentration yields

the hopping time of anthracene-triplet-excitons τhT = 3.2·10-12 s;

the detrapping rate ρ = 100 s-1,

and the decay rate o f the guest-triplet state βTG = 1250 s-1 .

The model calculations are also in agreement with measurements of other authors [2, 6].
Calculation of CNDO Characters Orders with Account of Virtual Pars Orbital Contributions
Authors: Fratev F. , Polansky O. E. , Nikolov P.
Published: February 2015

The contribution of virtual pars orbitals to the occupied molecular orbitals is taken into account in the CNDO approximation. On this basis a new index ϱ̄L is introduced, which is similar to the character order ϱL in the π-electron approximation. The calculated values of ϱ̄L for the 19 compounds under investigation correlate well with the experimental bond lengths, as well as with a number of other physical and chemical properties.
Notizen:MIND0 /3 -Parameter für die Bindungsenergie von H2/MINDO/3-Calculations of the dissociation of H2
Authors: Fleischhauer Jörg , Raabe G. , Thiele H.
Published: February 2015

The results of an ab initio calculation of the H2- and the exact values of the H2
+-binding-energies are compared with MINDO/3 values. The MINDO/3-parameters are then varied to give an optimal fit of the H2-energies as functions of nuclear distance.
Screening of Impurity Pseudopotentials in Polar Semiconductors
Authors: Renn W.
Published: February 2015

It is shown how the total pseudopotential of an impurity (and not its Coulomb potential only) is screened by the electronic and ionic polarization of the host crystal caused by the impurity itself. An atomic description of the host crystal and the static polarization is given by means of the dipolar model developed by Stumpf. The F-centre in alkali halides is treated as an example to test the method. For actual calculations, the BSG pseudopotential is used. Numerical results of the absorption and optical ionization energies are presented.
Defect Diffusion Models in NMR and Dielectric Relaxation
Authors: Kimmich Rainer , Voigt Gerhard
Published: February 2015

The effect of diffusing defects such as vacancies, displacements, torsions, and rotational isomers on the nmr and dielectric relaxation behaviour is treated under various aspects. The influences of the dimensionality of the diffusion process, of the mutual hindrance, of the defect concentration, of the defect length and of the mean lifetime are derived and discussed.
Further Study on the Forms of Umbelliferone in Excited State
Authors: Grzywacz Jerzy , Taszner Stanislawa , Kruszewski Jerzy
Published: February 2015

Absorption and emission spectra of umbelliferone in ethanol-water solution are studied in a wide range of water content. No variations in the absorption spectra were found, whereas the emission spectra proved to be highly sensitive to the volume percentage of water. An interpretation is attempted on the basis of electron density calculations by the SCF PPP CI method for the molecule of umbelliferone and a hypothetical tautomer.
l-Type Doublet Transitions of the Rare Stable Isotopic Species of Hydrogen Cyanide, HCN
Authors: Winnewisser Manfred , Vogt Jürgen
Published: February 2015

l-type doublet transitions for HCN molecules in the first excited bending state 0110 have been measured for the isotopic species H13C14N, H12C15N, H13C15N, D13C14N, D12C15N and D13C15N. The measurements improve and complete the set of available coupling constants of the vibrationrotation interaction in this bending mode. All known l-type coupling constants are collected and compared with those obtained from the l-type splitting of the rotational lines and those obtained from ab-initio calculation of the energy hypersurface.
The Microwave Spectrum of Methyl Selenocyanate (CH3SeCN)
Authors: Landsberg B. M.
Published: February 2015

The microwave spectrum of methyl selenocyanate has been observed for the isotopic species 12CH3
80Se12C14N, 12CH3
78Se12C14N, 12CH3
77Se12C14N, 12CH3
76Se12C14N, 12CH3
82Se12C14N, 13CH3
80Se12C14N and 13CH3
78Se12C14N.

For the main isotopic species, a full centrifugal distortion analysis is reported and internal rotation splittings have been analysed for the ground and first excited torsional states, and also for the ν10 = 1 and ν10 = 2 excited vibrational states. A structure based on a mixture of rs and ro arguments is reported, and also the principal components of the dipole moments.
Elementare Herleitung der Dirac-Gleichung / Elementary Derivation of the Dirac Equation
Authors: Sallhofer Hans
Published: February 2015

As is well known, the Schrödinger equation can be derived by suitably arranging the refraction in the classical equation for light inhomogeneous media. In this paper it is shown that one may derive the Dirac equation in complete analogy by arranging for the refraction in the electrodynamics of inhomogeneous media.
EPR of Gd3+ in Hydrated Double Nitrate Single Crystals
Authors: Jain V. K .
Published: February 2015

EPR of Gd3+ in Sm2Zn3(NO3)12 · 24 H2O and Pr2Mg3(NO3)12 · 24 H2O single crystals has been studied at X-band. In addition to the allowed fine structure lines (ΔM = ± 1) some weak low field lines identified as ΔM = ± 2 transitions, have been observed.
59Co NMR Studies of Rare Earth Cobaltites
Authors: Bose M. , Ghoshray A. , Basu A. , Kollali Sheelavathi , Rao C. N. R.
Published: February 2015

39Co NMR studies of rare earth cobaltites, LnCoO3 (Ln = La, Pr, Nd, Ho, Er, Yb, Y) have shown evidence for quadrupolar and hyperfine interaction effects in these systems.
On the Evaluation of Transport Collision Frequencies I. The Integration of Empirical Data
Authors: Weinert Ulrich , Kratzsch Klaus-Achim , Oberhage Heinz-Rüdiger
Published: February 2015

The computation of the transport collision frequencies is discussed, provided the transfer cross sections are given at least for a discrete set of relative kinetic energies. Numerical investigations show that the most satisfying results are achieved by the use of rational interpolation of the transfer cross sections.
Leistungseinkopplung in ein Plasma erhöhter Elektronentemperatur bei der unteren Hybridresonanz
Authors: Glomski G. , Heinrich B. , Schlüter H.
Published: February 2015

Previous investigations of lower hybrid resonant coupling to plasmas of low collision frequencies and elevated electron temperature are extended to cover a range of some mW to 1500 W of reactive power. Though resonant behaviour is observed throughout, the efficiency of power transfer is lowered when a threshold at about 1 Watt of reactive power is surpassed. Moreover there is a limited decrease of electron density. For high powers saturation in the drop of transfer efficiency is observed.
Neutron Slowing Down with Inelastic Scattering
Authors: Wakil S. A. El , Machali H. M. , Saad E. A.
Published: February 2015

The neutron slowing-down equation in an infinite homogeneous medium with isotropic scattering is solved. The slowing-down kernel is separated into an elastic and an inelastic part. The collision density is expressed in terms of Green’s function of the elastic scattering only. The Greuling- Goertzel (G-G) approximation is used for the elastic scattering kernel, while Volkin’s model is used for the inelastic one. A differential-difference equation for a one-level excited state is solved by Laplace transform. Discussion of the poles obtained in the Laplace inverse shows that there are forbidden zones in which there is no solution. Numerical calculations of the collision density in Fes6 at 922 and 865 kev levels are performed, which give the same behaviour as obtained by Corngold. The average slowing-down time calculated with our approach agrees with Williams’s result in the asymptotic solution.
Atomic Hydrogen in the Mineral Brasilianite NaAl3(PO4)2(OH)4
Authors: Hill Fritz , Lehmann Gerhard
Published: February 2015

EPR parameters for atomic hydrogen in three nonequivalent special positions at the twofold axis of the monoclinic structure of brazilianite, formed by X-ray irradiation at room temperature, are reported. The g-factors are practically isotropic and close to the free electron value, but the hyperfine splittings exhibit considerable anisotropy. One of the centers shows an additional doublet splitting, most likely due to hyperfine interaction with the proton of one of the OH groups. These hydrogen atoms have the highest thermal stability yet reported. With repeated thermal destruction and formation by ionizing radiation one of the centers is rapidly depleted. Thus they must be formed at defect sites, not from the undisturbed OH groups, and trapped near the sites of formation and their thermal destruction must at least in part be irreversible. Possible defects for their formation are discussed.
The Complete Substitution Structure of 1,2,5-Thiadiazole
Authors: Stiefvater Otto L.
Published: February 2015

Double Resonance M odulation (DRM) microwave spectroscopy has been used to determine the complete substitution structures of 1,2,5-thiadiazole and 3,4-d2-1,2,5-thiadiazole. The 34S-, 13C- and 15N-species o f these two “parent” molecules were studied in natural abundance. The structure parameters o f the two parent forms agree to within ± 0.0005 Å and ± 0.02° with the following averaged values:

Distances (in Å)

S - N = 1.6296

C = N = 1.3270

C - C = 1.4167

C - H = 1.0805

Angles (in degrees)

NSN = 99.44

SNC = 106.51

NCC = 113.77

CCH = 126.27

The new data confirm the earlier work on this substance, but the precision o f the structure parameters is improved by a factor of ~ 10. The apparent C-C bond length in the normal species is found to differ by ~ 0.001 A from that in the 3,4-d2-species. Vibrational contributions (⊿Ivib) to the effective changes of the moments o f inertia are determined for the sulphur atom and the near-axis nitrogen atoms as ⊿Ivib(S) = - 0.0017 μÅ2 and ⊿Ivib(N) = - 0.0035 μÅ2.

Energy transfer through collisions has been exploited to overcome traditional difficulties in the identification o f high-J Q-branch transitions o f rare isotopic forms.
Two-Photon Ionization of Polyatomic Molecules in a Mass Spectrometer
Authors: Boesl U. , Neusser H. J. , Schlag E. W.
Published: February 2015

Two-photon ionization of benzene molecules in a mass spectrometer is performed with a tunable frequency-doubled dye laser. The nonlinear ionization is resonantly enhanced by real intermediate rovibronic levels in the S1 state of the molecule. Our results show that stepwise multi-photon ionization is a very selective and versatile ionization source for a mass spectrometer.
Monte Carlo Simulation of the Interfaces Liquid-Crystal and Liquid-Rigid Wall
Authors: Borštnik B. , Ažman A.
Published: February 2015

The structure of liquids at liquid-crystal and liquid-rigid wall interfaces was studied by the Monte Carlo method on systems consisting of either 128 Lennard-Jones atom s or 128 hard spheres. The resulting density profile can serve as a reference for the approximative methods based on the BGYB hierarchy of integral equations. The pair correlation function close to the rigid wall is found to deviate appreciably from the bulk liquid pair correlation function. The maxima and minima of g(r) are more pronounced in the first two layers of atom s close to the rigid wall.
The Light Guide Effect of Planar Lipid Bilayers and Its Application to Bilayer Spectroscopy
Authors: Braun H. P. , Michel-Beyerle M. E.
Published: February 2015

The light guide properties of planar lipid bilayers offer a novel approach to bilayer spectroscopy. Potential applications are outlined.
Adsorption of Hydrogen on a Nickel (100) Surface
Authors: Christmann K.
Published: February 2015

The adsorption of hydrogen on a clean Ni(100) single crystal surface was studied in UHV between 120 K and 500 K means of LEED, thermal desorption spectroscopy and work function measurements. H2 chemisorption occurs in two atomic states β1 and β2 with maximum desorption rates (at saturation) at 318 K and 348 K. The activation energy for desorption was determined to be 20 (± 2) kcal/mole for the β1-state and 23 (± 1) kcal/mole for the β2-state, in excellent agreement with previous results. Saturation at 120 K corresponds to a coverage of 0.9 20%).

The initial sticking probability is 0.06 (± 0.01) and the rate of adsorption follows second order kinetics. No additional LEED spots arose from the H overlayer, indicating the absence of long-range order even at 120 K. The work function results clearly show the existence of two different binding states: Whereas the β2-population gives rise to a linear increase by 100 meV (at 120 K) the ß1-state leads to a decrease of ⊿ϕ to a final value of 30-40 meV.
Investigation by X-Ray Absorption Spectroscopy of Platinum Clusters Supported on Zeolites
Authors: Gallezot P. , Weber R. , Betta R. A. Dalla , Boudart M.
Published: February 2015

The onset of the LIII edge of the X-ray absorption spectrum of platinum in F-zeolites involves an electronic transition from core to band levels producing a so-called white line. The spectral area of this increases and the edge position shifts to higher energies, first when the platinum particle size becomes small enough so that the clusters are in the supercages, second when the clusters are covered with oxygen, and third when multivalent cations are introduced in the zeolite. Both features of the absorption edge indicate that under the three above circumstances, platinum becomes more electron deficient. This conclusion had been inferred earlier from the enhanced catalytic activity of Pt clusters in Y zeolites.
Charakterisierung von Silika (Aerosil) Hydrosolen durch Photonenkorrelationsspektroskopie / Characterization of Silica(Aerosil)Hydrosols by Photon Correlation Spectroscopy
Authors: Killmann E. , Eisenlauer J. , Kaniut P.
Published: February 2015

The diffusion of silica(Aerosil)-hydrosols has been studied by photon correlation spectroscopy. For data analysis the method of cumulants, proposed by Koppel, was used. Effects of charge and hydratation of the silica particles and their complicated aggregated structure required an extrapolation to the solconcentration cs = 0 and the scattering angle θ = 0.

The described data analysis combined with the methodical proceeding - using Aerosil aggregates as a model system - shows how to evaluate the diffusion coefficient and its normalized variance. These data of characterization are important for many kinds of aggregated particles in technical applied dispersions.
Chalcogen Interdiffusion in the System Pb(S, Se)
Authors: Leute Volkmar , Böttner Harald , Schmidtke Heinrich
Published: February 2015

From the sulfur-and selenium-concentration profiles recorded by an electron microprobe the chalcogen interdiffusion coefficient of the system Pb(S, Se) is determined as a function of mass fraction cPbse and temperature. Undoped crystals and Pb-or chalcogen-saturated crystals are studied. The dependence of the interdiffusion coefficient on the deviation from stoichiometry shows that in the chalcogen-saturated part of the system the calcogen interdiffusion proceeds via chalcogen interstitials, whereas in the Pb-saturated part of the system the chalcogens diffuse via chalcogen vacancies. For pure PbSe it is shown that these vacancies are doubly ionized. The activation entropy of the diffusion of the chalcogens depends linearly on the ratio of activation enthalpy to solidus temperature.
Dispersion der gekoppelten Wellen beim stimulierten Raman-Effekt in einfachen piezoelektrischen kubischen Kristallen
Authors: Merten L. , Wenk J.
Published: February 2015

Even in the most simple case of cubic piezoelectric crystals with only one polariton branch the problem of coupling of polariton, Stokes and anti-Stokes waves in the parametric approximation leads to six coupled waves, each consisting of a polariton component, a Stokes component and an anti-Stokes component. The dispersion of all six coupled waves can be described by explicit formulae in very good approximation. The shift of the dispersion curves of the coupled waves against the dispersion curves of the uncoupled waves is proportional to the square of the amplitude of the pump wave
UPS Spectra of Cis and Trans 1-Phenyl-2-(4-Pyridyl) Cyclopropanes. A Comparison with Charge Transfer and Protonation Data
Authors: Distefano G. , Modelli A. , Mancini V.
Published: February 2015

The low ionization energy region of the USP spectra of cis- and trans-1-(4-X-phenyl)-2-(4pyridyl) cyclopropanes is assigned by analogy with those of simple related molecules. Corresponding IE values of cis and trans derivatives are equal within the limits of experimental error. This finding indicates, at variance with solution results previously obtained, that in the gas phase there is no sizeable through- space interaction between the MO’s of the two cis-aryl groups. A possible explanation of the different conformations of the cis derivatives in the two phases is proposed
Evidence for Polymorphism within the So-called “Blue Phase” of Cholesteric Esters. I. Calorimetric and Microscopic Measurements
Authors: Bergmann K. , Stegemeyer H.
Published: February 2015

Calorimetric measurements as well as microscopic observations confirm the existence of two thermodynamically stable polymorphic forms of the so-called “blue phase” of cholesteryl nonanoate and myristate
Evidence for Polymorphism within the So-called “Blue Phase” of Cholesteric Esters. II. Selective Reflection and Optical Rotatory Dispersion
Authors: Bergmann K. , Pollmann P. , Scherer G. , Stegemeyer H.
Published: February 2015

In cholesteryl nonanoate the existence of two polymorphic forms of the so-called “blue phase” has been evidenced by selective reflection and optical rotatory dispersion measurements. The spectroscopic results indicate a discontinuous transition between the two phases
Zur Bildung und Umwandlung der „blauen“ und „grünen“ Zentren im goldaktivierten Zinksulfid / On the Formation and Conversion of “Blue” and “Green” Centres in Gold-Activated Zinc Sulphide
Authors: Kynev K. , Kuk V.
Published: February 2015

The phosphor ZnS-Au activated in the presence of zinc exhibits a blue emission band (Emax = 2,58 eV) which can be ascribed to associated Au′Zn-Vׄs-centres. A reversible interconversion of “blue” and “green” centres is achieved by retiring the phosphor samples in a suitable gas atmosphere
Lattice Vibrations and Ideal Electrical Resistivity of Noble Metals
Authors: Singh B. P. , Hemkar M. P.
Published: February 2015

The phonon dispersion in the three principal symmetry directions [ζ00], [ζζ0] and [ζζζ] and the temperature variation of the electrical resistivity of Cu, Ag and Au have been studied by using a lattice dynamical model which takes into account d shell-d shell central interactions up to second neighbours. The calculated results have been compared with the available experimental data and have been found to be in a satisfactory agreement.
Polarization, Barriers and Tunneling Times of Some Tautomers of Adenine and Thymine
Authors: Marañon Julio , Sorarrain Oscar M.
Published: February 2015

The polarization of the radiation involved in some transitions is analysed for the normal and tautomeric forms of adenine and thymine. Tunneling times for some barriers previously reported [1] and equilibrium constants between two isomers for some excited states are also given. The calculations have been made with the CNDO/2-CI method and the results compared with the available experimental data.
Networks Induced in Nonlinear Chemical Reaction System by Symmetries of Transformation Groups
Authors: Busse H. G. , Havsteen B. H.
Published: February 2015

Physical systems possess a structure and display dynamics. The article describes how a structure of one class of systems, which are encountered in chemical kinetics, can be revealed. The structure may be represented by a graph that has some similarities with the graph used to dis-play the structure of chemical molecules. The graphs are induced by one-parameter trans-formation groups in nonlinear systems. The model system of Dreitlein and Smoes is treated as an example.
Notizen: Mechanism of CaMoO4 Formation in the Solid State from CaO and MoO3
Authors: Flor G. , Berbenni V. , Massarotti V. , Riccardi R. , Tkacenko E. V.
Published: February 2015

The formation in the solid state of CaMoO4 from CaO (single crystal) and MoO3 was investigated by the contact method in the temperature range 625-710 °C and at 10−4 < po2 < 1 atm.

The relatively high velocity of this process compared with that for CaWO4 formation is explained on the basis of the different types of lattice disorder predominant in the two reaction products.

As concerns CaMoO4, the majority defect pair (VMo
6′, h·) was deduced by Wagner and Schmalzried's method.

The overall results indicate that the rate-determining step of CaMoO4 formation is the molybdenum diffusion via VMo
6′ .
Luminescent Heterocycles. IX pH Dependent Fluorescence Spectra of Chromone, 2-Methylchromone and 7-Hydroxy-2-Methylchromone [1]
Authors: Wolfbeis Otto S. , Knierzinger Andreas
Published: February 2015

The fluorescence spectra of the title compounds have been measured in the pH 9 to H0 -9 acidity range at 25 °C. Chromone and its 2-methyl derivative fluoresce intensely from their protonated form, whereas the uncharged molecules are nonfluorescent. Förster cycle calculations show chromone to be more basic in its first excited singlet state than in its ground state, but protonation proceeds incompletely during the lifetime of the excited molecule.

7-Hydroxy-2-methylchromone (7-HMC) fluoresces in water, depending upon the solvent acidity, from its anion and a zwitter-ion (or phototautomer or exciplex), but not from the neutral molecule. pKa, values are given for both the ground and excited state and drastic differences are found: The 7-HMC anion in its S1-state is first protonated at the carbonyl oxygen rather than at the phenolate oxygen.

Attention is drawn to the extrem solvent and acidity sensitivity of the fluorescence maxima and intensities of 7-hydroxy-chromones with respect to possible analytical determinations of naturally occurring derivatives using luminescence spectroscopy
Korrelationen zwischen PMO-Lokalisierungsenergien und PO-MO-Charakterordnungen benzoider Teilsysteme in polycyclischen aromatischen Kohlenwasserstoffen / Correlations between PMO Localization Energies and PO-MO Character Orders of Benzoid Part Systems of Polycyclic Aromatic Hydrocarbons
Authors: Zander M.
Published: February 2015

PO-MO character orders and PMO localization energies of benzoid regions of polycyclic aromatic hydrocarbons correspond to some extent in a significative way. On principle, the localization energy pattern of a given hydrocarbon can be understood on the basis of the pars orbital approach
The Influence of Molecular Transitions on the Spectrum of the Helium Line at λ= 447.15 nm in a Low-Pressure Discharge
Authors: Pinnekamp F.
Published: February 2015

In a linear pulsed discharge of helium the spectrum of the atomic transition 43D, F→23P at → - 447.15 nm is measured time resolved by a multichannel analyzer. Pronounced structures of the line profile, reported by other authors could not be verified and helium molecular lines did not occur in the parameter range of this discharge below 100 Pa. The measured influence of spurious hydrogen might suggest the interpretation of the recently observed structures as being due to hydrogen molecular transitions.
Chemisorption on a FCC Metal Surface: Electronic Structure of Ordered Overlayers
Authors: Masuda Kin-ichi
Published: February 2015

A Green's function perturbation technique is presented which is appropriate for studying the chemisorption behavior of ordered atomic layers on a metal surface. The phase shift technique is used to determine the change in the electronic density of states due to chemisorption. The method is quite general and can be used to study the electronic structure of arbitrary ordered overlayers. Numerical results are given for p(2x2), c(4x2), p(2x1), c(2x2) and p(1X1) overlayers on a (001) surface of a tight-binding fee metal. It is shown that the effects of long-range order and the binding geometry of the adsorbate layer are of great importance for the electronic structure of ordered overlayers.
Investigation of Methyl Reorientations in 1,4-Dimethoxy- 2,6-dimethylbenzene by NMR and Inelastic Neutron Scattering
Authors: Wind R. A. , Bovée W. M. M. J. , Kupers J. C. F. , Smidt J. , Steenbergen Chr.
Published: February 2015

In this paper a solid state NMR relaxation study and inelastic neutron scattering (INS) experiments (the latter in the solid and liquid phase) are reported for a molecule containing methyl groups in different surroundings, namely 1,4-dimethoxy-2,6-dimethylbenzene. The results are compared with each other and with those of a liquid state NMR study reported earlier. It is found that in this way both the shapes and magnitudes of the various hindering potentials can be determined.

The result is that the methyl groups 1, 2 and 4 possess a threefold cosine-shaped potential with heights given by 7.7, 9.0 and 15.0 kJ/mol according to the solid state NMR measurements (from the INS study the values 7.5, 7.5 and 16.0 kJ/mol were obtained). For methyl group 6 a mixture of a three-and six-fold symmetry had to be taken into account in order to explain the experiments. Except for methyl group 4 the liquid state NMR results deviate from those obtained with the other two techniques. A possible cause for this discrepancy is discussed.

For the molecular structure it is concluded that the reorientations of the methyl groups 1 and 2 are influenced by mutual hindering and that the angle between the plane through the C4-O-C bond and the aromatic plane is small, whereas for the C1-O-C bond this angle is estimated to be about 70°.
Dirac-Like Equation for the Photon
Authors: Silveira Adel da
Published: February 2015

A Dirac-like equation for the photon is considered by using a four-by-two matrix wave function. Conservation laws and transformation properties under Lorentz transformations are considered.
LEED Intensity Measurement by Photographic Method with Digital Image Processing
Authors: Ueda K. , Lehmpfuhl G. , Reuber E.
Published: February 2015

An accurate photographic method for measuring intensities on a fluorescent screen is described. Simultaneously with the fluorescent screen a calibrated 7-step grey scale is recorded on the film. Using a scanning photometer the intensity distribution can be digitized and by comparison with the grey scale converted to electron current density. As an example LEED-intensities from a Si (lll)-surface obtained with the photographic technique are compared with spot-photometer measurements.
Monte-Carlo-Simulation des Abklingverhaltens von Kristallen am Beispiel des Anthracens / Monte-Carlo-simulation of the fluorescence decay of anthracene single crystals
Authors: Ganz P. , Ganz S.
Published: February 2015

Computer Simulation of the fluorescence decay of an anthracene single crystal shows that strong reabsorption leads to nonexponential decay curves.
Kinetic Parameters from Thermogravimetric Data
Authors: Marini Amedeo , Berbenni Vittorio , Flor Giorgio
Published: February 2015

The "differential" method of Achar, Brindley and Sharp (ABS) and the "integral" one of Coats and Redfern (CR) are applied to the dehydration of BaBr2-H20 and HCOOLi-H20 and to the thermal decomposition of Pb(SCN)2, and the kinetic parameters so obtained are compared with those deduced isothermally. The results of the ABS method, at the lowest heating rate (q = 1.2 K min — '), agree well with the isothermal ones, whereas the CR method leads to satisfactory results only for the Pb(SCN)2 thermal decomposition (q = 1.2 K min~*). A possible explanation is given.
A Study of a Weakly Ionized Rotating Plasma
Authors: Wijnakker M. M. B. , Granneman E. H. A. , Kistemaker J.
Published: February 2015

Measurements are reported on a weakly ionized rotating argon plasma generated by two identical gas discharges facing each other. In each discharge a current up to 100 A is drawn between a point-like cathode and a ring-shaped anode. Axial magnetic fields up to 0.26 T are applied. All measurements have been done at 1 torr.

For magnetic field strengths below 0.17 T the plasma has a more or less uniform radial distribution; above 0.17 T a contracted plasma column is present along the axis of the cylinder.

In the symmetry plane between the two discharges measurements have been done on the rotational velocity of neutrals and ions, the electron density and temperature, the ion temperature, the plasma potential and the radial pressure distribution. The rotational velocity, the plasma potential and the pressure distribution are also calculated. The theoretical treatment is based on the theory developed by Klüber and Wilhelm and Hong.

In the low magnetic field case velocities of 700 m/sec are found for ions as well as neutrals. The agreement between theory and experiment is good in this case. At high magnetic fields, the ions and neutrals are found to have azimuthal velocities of 1900 and 700 m/sec, respectively.

The radial pressure enhancement due to the centrifugal forces is found to be approximately a factor of two whereas the theory predicts only a factor of 1.2.

In a discharge in which a mixture of argon and xenon is used a relative separation factor of 2.15 is found.
Adiabatic Potentials of the Alkali-Rare Gas Atom Pairs
Authors: Czuchaj E. , Sienkiewicz J.
Published: February 2015

The semiempirical potential-model calculations of Baylis have been repeated with some modifications. Firstly, an exact calculation of the Pauli exclusion pseudopotential for the repulsion between alkali core and rare gas atom has been carried out. Secondly, the new atomic radial orbitals proposed by Simons were taken for the calculation instead of those of the Bates-Dam-gaard type. The adiabatic potentials calculated here have, in general, a similar character as the previous ones obtained by Pascale et al. However, many of them are seriously modified.
Thermal Motion of Prolate Luminescent Molecules in Solvents with Different Viscosities
Authors: Kawski A. , Kamiński J. , Kukielski J.
Published: February 2015

The emission anisotropies r of the fluorescence of the prolate molecules 4-dimethylamino-4′-nitrostilbene (DNS) and 4-amino-4′-nitrostilbene (ANS) in solvents of different viscosities η were investigated. The non-linear dependence of 1/r on T/η was confirmed. Agreement between the experimental data and theory was obtained by the assumption that the prolate luminescent molecules perform irregular rotational motions within a limited solid angle. The theory developed for prolate molecules with the emission transition moment parallel to the long axis of the molecules describes well the experimental results. Rotational relaxation times in different solvents and effective volumes of the studied molecules were obtained.
Lattice Dynamics and Thermal Expansion of Ruthenium
Authors: Rao R. Ramji , Murthy J. V. S. S. Narayana
Published: February 2015

The lattice dynamics, lattice specific heat and thermal expansion of ruthenium are worked out using the model of Srinivasan and Ramji Rao, based on Keating’s approach. A total number of 50,880 frequencies has been used in constructing the frequency distribution function. The anharmonic parameters are obtained from the data of Clendenen and Drickamer on the pressure variation of the lattice parameters of ruthenium. The Anderson-Grüneisen parameter δ is calculated using the theoretical TOE constants, and the temperature variation of the bulk modulus is explained using Anderson’s theory.
Phasendiagramme von (NH4, M)X und(ND4, M)X mit M = Tl, Rb oder Cs und X=Cl oder Br / Phase Diagrams of (NH4, M)X and (ND4, M)X with M = Tl, Rb or Cs and X = Cl or Br
Authors: Brauer Peter
Published: February 2015

Phase transitions in (NH4, M)Cl with M=Tl, Rb or Cs and (ND4, Tl)Cl as well as (NH4, M)Br and (ND4, M)Br are measured using birefringence or differential thermal analysis. The phase diagrams of the mixed systems with M=Tl having decreasing lattice constant with increasing amount of Tl are similar to the well known T(P) diagrams. Therefore the diagrams of the sys­tems with M=Rb or Cs having increasing lattice constants correspond to T(P) diagrams in the range of fictitious negative pressure P. Substitution of D for H produces an effect similar to reducing the lattice constant. The extraordinary large negative isotope effect of II-III transitions and the appearance of the birefringent phase III in the chlorides are now understood.
Notizen: Orbital Binding Energies within the Statistical Exchange Approximation: Ne and Ar Isoelectronic Series
Authors: Sen K. D.
Published: February 2015

Binding energies are calculated using the orbital energies within the Kohn-Sham-Gaspar statistical exchange approx­imation for the Xe and Ar isoelectronic series, respectively. The results are generally in good agreement with the available Hartree-Fock orbital energies.
Notizen: A Contribution to the Stark-Spectroscopy at Low Microwave Frequencies
Authors: Schrepp W. , Dreizler H.
Published: February 2015

Recently we published a construction of a micro­wave-microwave double resonance spectrometer [1], which allows a variety of experiments. An essential part of it is a “stripline” absorption cell.

Although Stark-Spectroscopy [2] gave a very important impetus to the investigation of rotation spectra and is in use for three decades, measure­ments below 6.5 GHz are few in number compared to the frequency region above 6.5 GHz.

The reason is that generally the line intensity decreases at lower frequencies and the cross sections of the standard waveguides are larger. If one does not use special waveguides * a higher Stark voltage has to be applied to produce the necessary Stark field for modulation. This requires a rather powerful Stark square wave generator** to load and unload the capacity of the absorption cell.

Measurements in the low frequency region may be useful since at these lower frequencies the density of rotational spectra is sometimes considerably lower than at higher frequencies, which faciliates the assignement.

We noticed that the stripline cell, which transmits from DC to 18 GHz in a coaxial type mode, may be used for Stark-Spektroscopy by feeding the Stark voltage and the microwave simultaneously to the septum. After having finished our experiments, we noticed that S. Weisbaum [4] et al. measured the transitions 32 - 3a and 52 - 53 of HDO at 486.50 and 824.64 MHz, respectively, by a similar tech­nique. The radiofrequency was connected together with the Stark voltage to the septum of a conven­tional Stark cell.

In Fig. 1 we give the details of the set up. To combine the microwave and the square wave we use “monitor tees” *. The square wave is fed into the monitor port which transmits a 100 kHz square wave. For example, a residual square wave of 140 V is observed at the microwave port when applying a 400 V square wave. To prevent any influence of the square wave on the microwave sourcje we use a piece of waveguide as a high pass filter. At the output of the absorption cell another piece af waveguide acting as a high pass filter protects the detector cristal. The cell we used for the measurements presented in Table 1 and Fig. 2 is made of an X-band waveguide R100 (cut off for the TE10-mode 6.56GHz). The construction is similar to that given in Fig. 1 of the previous paper [1], but TNC connectors** are used. The cell has been tested for a voltage of 2500 V between septum and the waveguide walls. The attenuation of the microwave on the stripline between 0.4 and 2.4 GHz is about 1.5 dB.
On Centrifugal Distortion and Urey-Bradley Force Field of Chlorofluoromethane
Authors: Jaman A. I. , Nandi R. N.
Published: February 2015

A normal coordinate treatment of chlorofluoromethane has been performed in the Urey-Bradley force field model using the centrifugal distortion constants and the vibrational frequencies. Since the molecule has only one plane of symmetry (Cs), the symmetrized internal coordinates have not been used in the calculation. The effect of the angular redundancy has been rigorously treated and the derived force constants are in good agreement with those of other halogenated methane.
NMR Pulsed Field Gradient Study of Self-Diffusion in the Isotropic Phase of the Liquid Crystals MBBA and EBBA
Authors: Rollmann G. , Reinhart K. F. , Noack F.
Published: February 2015

In refinement of a previous study made by Hayward and Packer, the self-diffusion coefficients D of the nematogen liquid crystals MBBA and EBBA were remeasured in the isotropic phase by means of the NMR pulsed field gradient technique. In particular, the diffusion measurements were made for the first time at different Larmor frequencies. A comparison with results obtained recently on the same samples by NMR T1 relaxation analysis reveals a severe discrepancy. Since the gradient method gives results in essential agreement with optical spectroscopies, the observed discrepancy must be attributed to shortages of the relaxation analysis (incorrect models, insufficient experimental accuracy). It is also shown that D depends more strongly on the molecular weight m than m-1/2 .
Synthesis and Properties of a New Kind of One-Dimensional Conductors. 2. Extended Hückel Calculations on the Energy Band Structure
Authors: Seelig Friedrich Franz
Published: February 2015

The co-ordination polymer of tetrazaporphin (TAP) with a transition metal, say FeII , in its center and acetylide anion, C2
2⊖ , as an axial bidentate bridging ligand is taken as a model sub-stance for the new type of one-dimensional conductors introduced in the preceding communication of this series. Although the monomer shows D4h symmetry, this is reduced to C4v for arbitrary kz -values of the Bloch functions of the first Brillouin zone. From the irreducible representations a1, a2, b1, b2, and e only a1 and e have contributions from all components, namely TAP2⊖ , Fe2⊕ and C2
2⊖, so that for these races broad energy bands can be expected. The a2, b1, and b2 MOs of the TAP-FeII subunits are separated fairly well and have no counterparts in the C2
2⊖ bridges so that very narrow bands should arise. This is confirmed by an EH calculation. Unexpectedly the a1 bonds which have contributions from the σ-MOS of C2
2⊖ are broader than the e-bands which contain the two crossed π-MO systems of C2
2⊖ . The quantitative results of the nearly self-consistent iterative EH calculation indicate overlap of the energy bands near the Fermi level and fulfill thus one necessary condition for metal-like electrical conductivity.
An Investigation of the Positive Column of a Hollow Cathode Arc in a Magnetic Field. Part II
Authors: Janssen P. A. E. M. , Boeschoten F.
Published: February 2015

It is shown that the behaviour of the highly ionized and magnetized plasma in the positive column of the hollow cathode arc (described in Part I of this investigation) may be well explained with the macroscopic equations on basis of the MHD ordering (eEr ⪢ ⊿p/ne). In particular the rotation of the plasma column around its axis is properly described by an equation for the electrical potential.

Viscous effects (due to ion-ion collisions) play an important role in the transport of particles, momentum and energy. The strong shear in the plasma rotation goes along with an inwardly directed ion flux, oppositely to the "classical" outward ion flux (due to ion-electron collisions), thus leading to an improved confinement of the ions. As the electron viscosity is negligible, the electrons move outward with the "classical" velocity. The resulting non-ambipolar plasma transport leads to an inwardly directed current and the corresponding j X B force drives the plasma rotation against the friction of the ions (ion-ion and ion-neutral collisions).

The stationary power balance is well fulfilled by the ions, and within a factor two also by the electrons. Most of the power is handled by the electrons.
Energielücke bei Polymethinstreptocyaninen unendlicher Kettenlänge / The Energy Gap in Polymethinestreptocyanines of Infinite Chain Lengths
Authors: Tyutyulkov N. , Fabian J. , Polansky . E.
Published: February 2015

Extrapolation of the experimentally determined energies of the longest wavelength transition in the polymethinestreptocyanine series yields a value of 1.0 eV for the energy gap.