bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical Studies of Soot‐Formation Processes in Premixed Flames
Authors: Haynes B. S. , Jander H. , Wagner H. Gg. 
Published: July 2012

AbstractSoot formation in flat, premixed flames of ethylene, benzene, and pyridine with air is investigated using laser light scattering and fluorescence and extinction measurements. — In the earliest stages of the soot formation process in all of the flames examined, a fluorescent emission is excited by the laser (extending from 450 nm to beyond 700 nm when excited at 488 nm). In pyridine and ethylene flames their intensity increases downstream or remains constant. In benzene flames, it passes through a sharp maximum just as the first particles are detected by light scattering. Measurements of optical extinction by soot particles are complicated by broad‐spectrum gas‐phase absorption which may dominate the soot absorption early in the flame. This absorption is stronger at shorter wavelengths and appears to be related to the molecules responsible for the fluorescence observed in these flames. The continuum fluorescence is also responsible for the apparently high degree of depolarization of the elastically scattered light early in the flame. The actual depolarization of the light scattered from the soot particles is of the order of 1% for ethylene and pyridine, 0.2% for benzene flames. — Combination of the corrected particle extinction and scatter measurements yields values for the particle size and number density. Soot particles grow by surface growth which depends on the nature of the parent fuel, the mixture C/O ratio, and the temperature and by coagulation. The measured coagulation rated are largely independent of these parameters and in agreement with the rates predicted from kinetic theory.
A New Estimate of the H+ Ion Concentration in Pure Water. Part 2. Numerical Results and a New Interpretation of the Limiting Equivalent Conductance of HCI
Authors: Hertz H. G. 
Published: July 2012

AbstractLinear response theory is applied to calculate the specific conductance of pure water. Comparison of velocity cross‐correlation coefficients with self‐diffusion coefficients yields a velocity correlation defect δH+ = 5.7 · 10−9. This figure is reformulated to give a H+ concentration of 3.18 · 10−7 mol/l in pure H2O at 25°C. A new interpretation of the limiting equivalent conductances of HCl and KOH involving the collective motion of all ions in the bulk of the solution is given. Then a new mode of understanding the transport numbers tp and tOH in aqueous HCl and KOH solutions is presented. Finally, the Grotthus mechanism is considered under the aspects of the present theory.
Photoelectrochemical Reactions and Formation of Inversion Layers at n‐Type MoS2‐, MoSe2‐, and WSe2‐Electrodes in Aprotic Solvents
Authors: Kautek W. , Gerischer H. 
Published: July 2012

AbstractCapacity measurements and cyclic voltammetry have been used to conduct a systematic investigation of the potential distribution at the semiconductor‐organic electrolyte interface in the dark and under illumination with the n‐type synthetic layered compounds MoS2, MoS2, and WSe2. From the obtained flat band potentials it could be concluded that the valence band edges vs. Ag/Ag+ are located in acetonitrile at ca. 1.0 V (MoS2), 0.7 V (MoSe2), and 0.4 V (WSe2). As theoretically expected, the oxidized component of redox systems with Fermi levels near or below the valence band edge can inject holes thus inducing an inverted region and generating a p‐n junction in the solid. The cathodic current in the cyclic voltammograms of such redox systems occurs via hole injection with consecutive recombination of the injected holes while less oxidizing redox systems can only be reduced via the conduction band. — Since the semiconductors used in these experiments do not corrode in presence of a high surface concentration of holes, such a contact with an oxidizing redox electrolyte offers most favourable conditions for the application in a photoelectrochemical solar cell. The inversion layer has a maximal band bending and promises to obtain the highest possible photovoltage, which is however limited by the width of the band gap.
Die zweiten Virialkoeffizienten verschiedener Gasmischungen im Temperaturbereich von 213 bis 475 K
Authors: Schmiedel H. , Gehrmann R. , Schramm B. 
Published: July 2012

AbstractEs wurden die zweiten VirialkoeffizientenBm(T,x1) der binären Gasmischungen NeAr, NeKr, NeXe, ArN2, ArCO und ArCO2im Temperaturbereich von 213 bis 475 K bei verschiedenen Molenbrüchen gemessen und aus diesen Werten der molenbruchunabhängige MischvirialkoeffizientB12(T) bestimmt. Die Meßdaten werden mit Virialkoeffizienten verglichen, die aus Potentialvorschlägen anderer Autoren berechnet worden sind.
Atomization Enthalpies of the Molecules Cu3, Ag3, and Au3
Authors: Hilpert K. , Gingerich K. A. 
Published: July 2012

AbstractThe gaseous species in equilibrium with Cu(l), Ag(l), and Au(l) were investigated by vaporization studies according to the method of high temperature mass spectrometry with a Knudsen cell. From the observed ion intensity ratios of dimer to monomer and of trimer to monomer the dissociation enthalpies of Cu2, Ag2, and Au2 were redetermined. The following atomization and sublimation enthalpies for the trimer in kJ mol−1 could be additionally determined by assuming a linear structure for these molecules: D00(Cu3) = 294 ± 13, D00(Ag3) = 253 ± 13, D00(Au3) = 367 ± 13, δsubH00(Cu3) = 714 ± 13, δsubH00(Ag3) = 598 ± 12, and δsubH00(Au3) = 737 ± 13. At the mean temperature of the measurements of 1849 K (Cu), 1500 K (Ag), and 1883 K (Au) the vapour pressures of the trimers are by a factor of 2.4 · 107 (Cu3), 2.9 · 107 (Ag3), and 1.7 · 107 (Au3) smaller than those of the corresponding monomers.
Ostwald Ripening of Precipitates. II. The Irreversible Thermodynamics
Authors: Chan Sai‐Kit 
Published: July 2012

AbstractIt is shown that the Lagrangian in the path integral solution of I to the differential equation of Ostwald ripening is the sum of the dissipation potentials in the flux and force representations minus the rate of entropy production. Minimization of the Lagrangian leads to the conclusion that the size distribution evolves with time in accordance with Onsager's principle of least dissipation. The stability criterion for evolution of Glansdorff and Prigogine is also examined in the context of the Ostwald ripening process and is found to be satisfied by all particles during the growing phase of their life spans.
Determination of Diffusion Coefficients by Electrochemical Current‐Time Measurements
Authors: Heinze Jürgen 
Published: July 2012

AbstractA considerably improved method has been developed for the absolute determination of diffusion coefficients from current‐time measurements. It is based on the use of stationary finite disk electrodes. Until recently, the current functions for these could be only approximately determined; they have now been calculated exactly by numerically solving the two‐dimensional diffusion equation. The same simple experimental conditions for apparatus and measuring apply as are usual for routine electroanalytical measurements. The experimental results are in close agreement with the classical data of Stackelberg et al. [8]. To facilitate evaluation and interpretation various working curves are presented.
Photochemische Zersetzung von gasförmigem Schwefelkohlenstoff als Störeffekt bei Gas‐Lasern
Authors: Steidl H. , Mikenda W. , Derkosch J. , Heresch F. 
Published: July 2012

AbstractEs wird über eine photochemische Reaktion von gasförmigem CS2 berichtet, die erstmals im Inneren eines Laserresonators beobachtet wurde. Die Reaktion führt bereits bei extrem geringen CS2‐Konzentrationen (< 10 ppm), die durch Diffusion in das Innere des Resonators gelangen, zum Auftreten kleinster Aerosolteilchen, die infolge starker Lichtstreuung die Laseremission beeinträchtigen und sogar zum Erliegen bringen können. Die Reaktion wird durch den UV‐Anteil des Plasmalichtes (λ < 380 nm) bewirkt und kann auch durch andere Lichtquellen, die in diesem Bereich genügend Leistung aufweisen, initiiert werden. Die streuenden Teilchen wurden als Schwefel identifiziert, doch konnte auch das Entstehen von COS und H2S nachgewiesen werden.
Excess Enthalpies of Liquid Alkane Mixtures at Pressures up to 500 bar. II. Extension and Application of a Molecular Theory
Authors: Heintz A. , Lichtenthaler R. N. 
Published: July 2012

AbstractThe Prigogine‐Flory‐Patterson‐Theory and its applicability in predicting thermodynamic excess properties is tested. In particular the experimentally determined dependence of the excess enthalpyHEon pressure of some binary alkane mixtures is used in this investigation. A consistent description of the experimental results is only possible using a modified form of this theory, which accounts for the short range order observed for n‐alkanes. The development of the extended theory is presented and the new insight possible into the molecular structure of the liquids and their mixtures under investigation is discussed.
ESR Studies on the Reduction Process of Silver Zeolites
Authors: Hermerschmidt D. , Haul R. 
Published: July 2012

AbstractIt is shown by in situ ESR studies that H2 reduction of dehydrated AgA‐ and AgX‐zeolites proceeds via intermediate formation of Agn+6 (n < 6) clusters, located inside the cubooctahedral sodalite cages. On further reduction, submicroscopic Ag crystals (<5 nm) are formed, resulting in a conduction electron spin resonance signal. At higher temperatures (T > 200°C) crystal growth leads to larger crystallites (10–50 nm) as indicated by x‐ray line broadening.
Eine neue Potentialfunktion — das n‐exp‐6‐8‐Potential
Authors: Leicht D. , Lucas K. 
Published: July 2012

AbstractFour potential functions with small number of parameters are tested in a systematic way with respect to their abilities to correlate and extrapolate data as well as to the physical significance of their parameters. Since none of these functions was satisfying as a whole, a new, more flexible function was introduced and investigated. Although the new function is only slightly better in terms of correlation and extrapolation, it can be shown, that it offers improvements in the values of the potential parameter and in the sensitivity of these parameters to data fitting.
The dual fluorescence of p‐substituted dialkylanilines: The twist mechanism occurs even in inert solvents
Authors: Wermuth G. , Rettig W. , Lippert E. 
Published: July 2012

AbstractIn nonpolar solvents p‐diethylaminobenzoic acid ethyl ester presents multiple fluorescence. The considerable temperature and viscosity dependence of the fluorescence quantum yields as well as solvatochromic effects on the long wavelength fluorescence FA make evident that the multiple fluorescence is to be traced back to the formation of a highly polar TICT (Twisted Intramolecular Charge Transfer) state.
Quantum rate theory of relaxation in symmetrical microscopic systems II: Preparation of initial states
Authors: Brickmann J. 
Published: July 2012

AbstractThe preparation process of initial quantum states for the relaxation in symmetrical molecular complexes is studied theoretically. It is shown that the possibility of preparing a definite quasistable molecular complex is drastically dependent on the magnitude of the minimal experimental error to detect this complex in real measurements. Consequences of the theory on the existence of classical and non classical structures of the 2‐norbornyl cation as intermediate complex in chemical reactions are discussed.
Das binäre System H2SO4—H2O;p,v, T‐Daten und Dampfdruckkurven in weiten Konzentrationsbereichen bei erhöhtem Druck
Authors: Giazitzoglou Z. , Wüster G. 
Published: July 2012

AbstractThe binary system H2SO4 — H2O has been investigated. p,v, T‐data of the pure vapour phase including five concentrations (y) 19.94, 39.72, 61.07, 77.04, and 98.92 Mol‐% H2SO4, a density range (1/v) from 1.1 to 38.3 g/1, pressures (p) up to about 50 bar, temperatures (T) up to 823 K, have been determined experimentally. Beside p,T,x‐data of the liquid phase were measured in a range of concentration (x) between 30.0 and 98.39 Mol‐% H2SO4 with pressures up to 50 bar and temperatures up to about 723 K. All experimental results are correlated using suitable equations.
Molecular interactions of hydrocarbon alkyl groups with carbon tetrachloride observed in the 13C NMR chemical shifts
Authors: Jackowski Karol , Kçki Zbigniew 
Published: July 2012

AbstractThe 13C NMR chemical shifts of n‐hexane, 2,3‐dimethylbutane, and 2,2,3,3‐tetramethylbutane solutions in cyclohexane and carbon tetrachloride were measured. The significant changes of chemical shifts were interpreted in terms of collision interactions, the nature of which was proposed to be the quantum mechanical exchange repulsion.
Shock tube measurements of the reaction behaviour of acetylene with O‐atoms
Authors: Löhr R. , Roth P. 
Published: July 2012

AbstractBy the direct measurement of the time dependent concentrations of H‐ and O‐atoms in the reaction zone behind shock waves using the ARAS‐technique, the reaction behaviour of acetylene with O‐atoms in the temperature range 1500 K ≤ T ≤ 2570 K at pressures of about 2 bars was investigated. The gas mixtures used consisted of argon with small initial concentrations of N2O (10 ppm to 100 ppm) and C2H2 (10 ppm to 25 ppm). Under the present conditions the results indicate a dominant influence of the reaction channels magnified image Which can be directly followed by the experiment. A good interpretation of the measurements is possible using the reaction rate coefficients

Extensive computer simulations with different models of secondary reactions show the dominant influence of the two given reaction channels for the present conditions and yield a practically perfect fit of the experimental values.
Partial information about the Mn2+‐CI−, Mn2+‐Br2+, and Mn2+‐BF4−pair distribution function together with the exchange dynamics from nuclear magnetic relaxation studies
Authors: Helm L. , Hertz H. G. 
Published: July 2012

AbstractWe report experimental results for the longitudinal and transverse relaxation rates of the35Cl and81Br nuclear magnetizations in aqueous electrolyte solutions containing the paramagnetic ion Mn2+as a function of the temperature and frequency.19F longitudinal relaxation rates are also reported for aqueous solutions of NaBF4+ MnBr2as a function of temperature and frequency. Using standard procedure the first coordination number of Mn2+with respect to the three anions mentioned are determined. Furthermore, residence times of these anions in the first coordination sphere are derived from the experimental data. Other auxiliary data like quadrupolar relaxation rates, electron spin relaxation times and scalar coupling constants are also reported and discussed.
Radiation‐electrochemistry of the colloidal gold micro‐electrode: Hydrogen formation by organic free radicals
Authors: Westerhausen J. , Henglein A. , Lilie J. 
Published: July 2012

AbstractVarious organic free radicals as well as Ni+ ions produce hydrogen in the presence of some 10−4 M of colloidal gold. The gold catalyst was prepared via the reduction of HAuCl4 either thermally by citrate or by y‐irradiation. The organic radicals were radiolytically produced. The mechanism of H2 formation includes electron transfer from the organic radicals to the gold particles, storage of a large number of electrons per gold particle, conversion of the electrons into adsorbed H‐atoms and desorption of the latter to form H2. — The rates of some of these steps were measured using the method of pulse radiolysis. 1‐Hydroxy‐1‐methyl ethyl radicals, (CH3)2COH, react with colloidal gold particles almost diffusion controlled provided that the gold particles are not charged with excess electrons. Charged gold particles react at a substantially lower rate. The stored electrons live seconds or even minutes depending on their number per gold particle. In the stationary state, up to 0.38 Coulomb of electrons could be stored per liter of a 2.9 · 10−4 molar gold solution, each gold particle carrying about 39 electrons. A comparison is also made between the catalytic activities of colloidal gold and silver. Due to the relative fast conversion of electrons into adsorbed H‐atoms, colloidal gold has less capacity for the storage of electrons than colloidal silver. — The dependence of the hydrogen yield on the pH of the solution, the concentration of gold, the size of the gold particles, the concentration of the polyvinyl alcohol stabilizer, and the intensity of radiation was also investigated. At high intensities, some of the radicals are destroyed in a gold catalysed disproportionation.
Electronic structure and transport in expanded mercury and in mercury‐xenon mixtures
Authors: Cheshnovsky O. , Even U. , Jortner Joshua , Hensel F. 
Published: July 2012

AbstractWe have compared the D.C. conductivity and the low‐concentration optical absorption coefficients of the two‐component Hg/Xe metal rare‐gas mixtures (MRGSM) and the one‐component expanded Mercury, the properties of both materials being expressed on a common density scale. For the density range corresponding to the strong scattering regime the transport properties of both materials are surprisingly similar. At high Xe concentration the polarization effects of the Xe atoms are of considerable importance, resulting in marked deviations between the transport properties of those two types of materials.
Cis→trans‐photoisomerization of thioindigo
Authors: Memming R. , Kobs K. 
Published: July 2012

AbstractThe mechanism of the cis→trans‐photoisomerization was investigated. Quantum yields of nearly unity were observed at temperatures around 180 K indicating that a twisting of the molecule excited into its S1‐state occurs. A detailed analysis has shown that both, an isomerization via the singlet as well as via the triplet state is possible. A kinetic model has been proposed which describes quantitatively the experimental results.
Über Beiträge einzelner Elektrodenprozesse zur Impedanz
Authors: Göhr Hermann 
Published: July 2012

AbstractAn electrode process is directly contributing to the impedance only in the case of its flux and its generalized force being connected with a charge transport and a voltage resp. (“electric process”). E. g. conduction and transfer reactions cause resistances, charging processes in the simplest case cause capacitances. Complications by gradients (e. g. of conductivity) within the dielectric are discussed. — A contribution to the impedance by another process appears provided that such a concentration is altered by it, the rate of an “electric process” depends on, too. Especially this is the case with common reactants. The kind of coupling is effecting a dependence of the contribution to the impedance on data of both processes. — The elements of impedance are determined by parameters independent of frequency, the meaning of which is discussed. In case of elements depending only on one parameter, it is a resistance, a capacity, a Warburg‐parameter, or an inductivity. Additional parameters have the meaning of rate or time constants or a geometrical meaning. From all parameters kinetic data of the electrode processes occurring are available. Therefore, the task of evaluation of impedance spectra may be understood as estimation of the values of these parameters.
Decomposition of carbon monoxide and its reaction with hydrogen on iron films under static conditions at pressures between 2 and 25 mbar and at temperatures between 373 and 573 K
Authors: Wedler G. , Körner H. 
Published: July 2012

AbstractWhen carbon monoxide is adsorbed on iron films at temperaturesT≥ 373 K carbon dioxide and carbon are formed. The Boudouard equilibrium is, however, not established at the chosen reaction conditions. In the presence of hydrogen the carbon monoxide adsorption leads to the formation of methane, carbon dioxide, and water. There is no correlation between the formation of water and of methane. The methane formation increases with both the increase in the total pressure and the increase in the partial pressure ratiopH2:pco. The ratio of the partial pressures of CO, H2, CO2, and H2Opoint to the establishment of the water gas equilibrium at medium temperatures.
Nuclear magnetic relaxation as indicator in oscillating chemical reactions
Authors: Schlüter A. , Weiss Alarich 
Published: July 2012

AbstractThe nuclear magnetic relaxation titrations is applied to study the oxidation of malonic acid with BrO3⊖in the presence of Mn3⊕/Mn2⊕as catalyst. The maximum amplitude of the free induction decay in a 180°‐τ‐90°1H‐NMR pulse experiment is used as a measure for the spin‐lattice relaxation rate 1/T1. Thereby, the oscillating nature of the reaction can be followed up conveniently. It is shown that the reduction Mn3⊕→ Mn2⊕in this reaction is of first order with respect to the concentration of Mn3⊕.
The Heats of Formation of Some Sodium and Barium Vanadates and Molybdates
Authors: Kubaschewski Oswald , Hoster Thomas , Schlim Roger 
Published: July 2012

AbstractAn isoperibol room‐temperature calorimeter has been constructed to measure the spontaneous reactions of BaO and Na2O with MoO3 and V2O5 after ignition. With this calorimeter, the heats of formation from the component oxides have been determined for BaMoO4, BaV2O6, Na2MoO4, Na2Mo2O7, NaVO3, Na4V2O7 and Na3VO4.
Entmischungsverhalten von Ethylen und niedermolekularem Polyethylen
Authors: Spahl Roland , Luft Gerhard 
Published: July 2012

AbstractThe reciprocal solubility of ethylene and polyethylene‐wax was determined at temperatures from 383 to 473 K under pressures up to 200 MPa. Besides the cloud curve, the shadow and the coexistence curves have been measured. The miscibility gap is present in the whole range of concentration for pressures under 65 MPa. The heterogeneous region increases slightly with rising temperature, the critical curve remains practically unchanged with varying temperature. The solubility of ethylene in the polymer could be described with good accuracy on the bases of Henry's law and the theory of Flory‐Huggins for solutions of polymers. This description can be made by means of a simple expression for the temperature and pressure dependency of Flory's parameter. The phase behaviour of the investigated system is compared with experimental measurements and with those of other authors carried out on mixtures with ethylene and alkanes having lower molecular weights.
Reductive and Non‐Reductive Effects of Cosensitizers on the Rhodamine B‐Sensitized Charge Separation at CdS Surface
Authors: Watanabe T. , Takizawa T. , Honda K. 
Published: July 2012

AbstractOrigin for the enhancement effect of hydroquinone (HQ), Fe2+, I−, Br−, and Cl−(cosensitizers) on the efficiency of electron injection from excited rhodamine B (RhB) to CdS has been investigated by combination of photoelectrochemical and heterogeneous photochemical measurements. The results indicate that the enhancement of RhB‐sensitized charge separation by HQ, Fe2+, and I−is due to reductive regeneration of the dye, while that by Br−and Cl−is mainly due to increased RhB adsorption at the CdS/aqueous solution interface.
On the Use of Resonant Raman Intensities and Bond‐Order Calculations to Refine Molecular Force Fields
Authors: Peticolas Warner L. 
Published: July 2012

AbstractIn this paper a theory is presented for calculating the resonant Raman intensities for all 3N‐6 molecular vibrations of a molecule excited by a Π → Π* electronic transition using only the known geometry of the molecule, the force constants (i. e. force field) for the internal coordinates and a molecular orbital calculation of all of the C‐ C and C‐ N bond orders in the ground and excited electronic states. Criteria are presented for the refining of a force field on the basis of observed and calculated resonant Raman intensities. — The method has been applied to 1‐methyl uracil. excited states which occur at 260 nm and 190 nm. The calculated intensities are compared with measured resonant Raman intensities using exciting light at 266 nm, 257 nm, and 212.8 nm. The agreement is satisfactory in that only the observed resonant Raman bands are calculated to have intensity.