bluuebunny/crossref_metadata_2025_split huggingface dataset:
Schwingungsspektroskopie von Molekülkristallen: Die zwischenmolekularen Kräfte im kristallinen Melamin (1, 3, 5‐Triamino‐s‐triazin) und ihr Einfluß auf die Infrarot‐ und Raman‐aktiven Molekül‐ und Gitterschwingungen
Authors: Schneider J. R. , Schrader B. , Bleckmann P. 
Published: September 2012

AbstractFür das kristalline Melamin (1, 3, 5‐Triamino‐s‐triazin, C3N6H6) wird mit Hilfe von zwischenmolekularen Potentialfunktionen V = ‐ A/ r6 + B exp( ‐C · r) die Lage der Wasserstoffatome und die Sublimationsenthalpie berechnet. Die zweiten Ableitungen dieser Potentialfunktionen werden als zwischenmolekulare Kraftkonstanten für eine Normalkoordinatenanalyse verwendet. Diese ermöglicht die Zuordnung aller in den Infrarot‐ und Ramanspektren beobachteten Banden. Trotz der weitreichenden Vernachlässigungen ergibt sich damit ein gutes Bild der statischen und dynamischen Wechselwirkungen der Moleküle im Gitter. Weiter zeigt es sich, daß der wechselseitige Einfluß der Moleküle bei den Gitterschwingungen so groß ist, daß entgegen der Voraussage nach der bisher akzeptierten Theorie eine reine Translationsschwingung sehr stark Raman‐aktiv ist.
Specific heat of binary liquid mixtures near the critical mixing point
Authors: Klein H. , Woermann D. 
Published: September 2012

AbstractThe temperature dependence of specific heat c at constant pressure P of mixtures of critical composition xc of the systems methanol/ n‐heptan and isobutyric acid/water is measured in an isothermal Calvet calorimeter. Near the critical mixing temperature Tc(T > Tc) the temperature dependence of c of both systems can be represented by a logarithmic singularity to a good approximation, i.e. c ∼ ϵ−α; ϵ = (T – Tc)/Tc; 0 ⩽ α ⩽ 0.1 The values of excess specific heat near Tc calculated from the Fixman theory are in satisfactory agreement with the experimental data.Measurements of the temperature dependence of coefficient of thermal expansion αc of the system isobutyric acid/water show that αc diverges weakly. The critical exponent of αc has the same value as that of specific heat within the accuracy of the experiments (0 ⩽ α ⩽ 0.1). This is in agreement with postulates of Griffiths and Wheeler. The singular part of αc of the system isobutyric acid/water is negative (αc ∼‐ϵ−α). From this observation and theoretical considerations of Griffiths and Wheeler it can be predicted that the critical temperature of the system isobutyric acid/water should decrease with increasing pressure. This is in agreement with experimental data reported in the literature.
Zur Thermodynamik quasiternärer Mischphasen. I. Mittlere Freie Enthalpie und Spinodale
Authors: Leute Volkmar , Stratmann Wilhelm 
Published: September 2012

AbstractUnter der Annahme streng regulären Verhaltens wird für quasiternäre Legierungssysteme die mittlere Freie Enthalpie als Funktion der Molenbrüche der beiden Untergitter hergeleitet. Mit Hilfe einer geeigneten Koordinatentransformation wird das temperaturabhängige Verhalten der Spinodale eines quasiternären Systems untersucht.
Mechanisms of Non Resonance Vibronic Coupling in Polyatomic Molecules
Authors: Brickmann Jürgen 
Published: September 2012

AbstractThe influence of non resonance vibronic coupling of two excited molecular states on the electronic absorption and emission spectrum is discussed in terms of low order perturbation theory. Transition probabilities are calculated taking into account a non totally symmetric coupling mode and a totally symmetric vibration with a displacement of equilibrium position in different electronic states. While band progressions in the emission and absorption spectra can be analyzed in terms of the Herzberg Teller (HT)‐theory, the ratio of HT‐intensities of orbitally “forbidden” transitions in absorption and emission has to be corrected by a factor due to the violation of the Born‐Oppenheimer (BO) approximation. The HT transition probabilities and the non‐BO correction factor are obtained in terms of spectroscopic properties. As a consequence it is possible to decide which vibronic coupling mechanism plays the dominant role in a given case. The calculated values are in good agreement with available experimental results.
A New Photovoltaic Effect Observed for Metal‐coated Semiconductor Electrodes and Its Utilization for the Photolysis of Water
Authors: Nakato Yoshihiro , Abe Koichi , Tsubomura Hiroshi 
Published: September 2012

AbstractThe photoelectrochemical behaviors of semiconductor (n‐GaP) electrodes coated with thin, semi‐transparent metal films have been studied. It has been found that the behavior of the n‐GaP electrode coated with gold at a low evaporation speed is quite different from that coated at a high evaporation speed. The former shows oxidation‐reduction waves similar to that of a gold electrode. The photocurrent‐potential curve observed for the latter electrode has an onset potential similar to that of a bare GaP electrode, but its photocurrent is quite steady and the electrode causes no anodic dissolution. A tentative model has been presented to explain the behavior of this new electrode, assuming that the metal film in this case is so coarse that the electrolyte solution can soak into it and reach the surface of the n‐GaP semiconductor.The usefulness of this new electrode is demonstrated by constructing an electrochemical photocell using this electrode, with which water can be photo‐decomposed into oxygen and hydrogen. This photo‐cell works under illumination in the visible region (λ < 550 nm), with the quantum yield of photocurrent of about 20–30% or more under illumination at 420 nm and 0.1 mW/cm2.
Electrochemical Reactions Involving Holes at the Illuminated TiO2 (Rutile) Single Crystal Electrode
Authors: Dutoit E. C. , Cardon F. , Gomes W. P. 
Published: September 2012

AbstractThe behaviour of several reactants at the illuminated TiO2 anode has been investigated. Current multiplication, indicating a two‐step electrochemical oxidation mechanism in which both the valence and the conduction band of rutile are involved, was found with several inorganic and organic reactants. From the study of competitive electrochemical processes, it was concluded that several other reactants are oxidized by holes solely. In certain cases, it has been possible to obtain quantitative data concerning relative hole reactivities. Possible reaction schemes, the origin of the ρH‐dependence of the multiplication factor, and the applicability of the direct electron transfer model to the reactions observed are discussed.
The Capacity of Passivated Iron Electrodes and the Band Structure of the Passive Layer
Authors: Stimming U. , Schultze J. W. 
Published: September 2012

AbstractThe capacity of passivated iron electrodes was measured by the potentiostatic pulse method in dependence on the oxide layer thickness d and the electrode potential ϵ at ρH = 8.4. At constant d, the C(ϵ) dependence shows three characteristic ranges. With increasing potential, C decreases in the first range by a factor 2, in the second range it becomes constant, and finally C increases at high potentials. The results are discussed with respect to the band structure model of the semiconducting passive layer. In the first range a Schottky‐Mott type behaviour is found indicating donor concentrations N up to 1020 cm−3. The flat band potential ϵFB = 0.1 V is obtained. In the second range, C is proportional to 1/d. The capacity increase in the third range at high potentials is explained as a contribution from valence band charging at the oxide surface. The band gap Eg = 1.6 eV follows. The electronic properties of oxide covered metal electrodes are discussed in relation to bulk semiconductor electrodes.
Emissionen von NH und ND (b1Σ+ → X3Σ−) aus der fensterlosen Einwirkung einer Ar‐Entladung in einem Strömungssystem
Authors: Zetzsch C. , Stuhl F. 
Published: September 2012

AbstractDie Fluoreszenzspektren metastabiler Imino‐(b1Σ+)‐Radikale aus der Einwirkung einer Ar‐Entladung auf NH3 und ND3 wurden im Bereich von 447 bis 484 nm vermessen. Erstmals wurden schwingungsangeregte metastabile Iminoradikale (für NH* mit ν ≤ 3, für ND* mit ν ≤ 4) beobachtet. Rotations‐ und Schwingungskonstanten der Elektronenzustände wurden aus den Spektren bestimmt. Für die elektronische Energie des (b1Σ+)‐Zustandes ergeben sich die Werte ν00 = 21238,5 ± 2 cm−1 für NH und ν00 = 21224,7 ± 2 cm−1 für ND.
Proton Conductivity and Thermoelectric Effect in Magnesium Hydroxide
Authors: Freund Friedemann , Hösen Rudolf 
Published: September 2012

AbstractThe d.c. conductivity ∑(T) and the thermoelectric effect U(T) of high purity Mg(OH)2 powder were measured under dry N2/H2 gas at atmospheric pressure using Pd/H electrodes. When a field gradient in the order of 104 V / cm is applied, proton conductivity ∑p is observed between 170—240°C with a maximum around 210°C, superimposed to a background conductivity ∑0 of probably electronic nature due to transition metal impurities. The activation energy for the linear portion in the log ∑p vs. T−4 plot was found to be 2.1 eV. The thermoelectric effect U(T) gave positive potentials over the wole temperature range studied which corresponds to a p‐type semiconductor. Again between 170–240 °C a protonic contribution Up was found with a maximum around 225 °C. Its activation energy is also 2.1 eV. The results are consistent with the model of a proton tunnelling mechanism in Mg(OH)2 as a precursor to its decomposition to MgO.
Absorptionsspektren von halogenierten Methanen im Bereich von 275 bis 160 nm bei Temperaturen von 298 und 208 K
Authors: Hubrich C. , Zetzsch C. , Stuhl F. 
Published: September 2012

AbstractDie Absorptionsspektren der halogenierten Methane CCl3F, CCl2F2, CHCl2F, CHClF2 und CH3Cl wurden im Wellenlängenbereich von 275 bis 160 nm bei 298 und 208 K bestimmt.
Kinetic Isotope Effect for the Reaction of a Hydrogen Atom with Cyclohexane‐h12, Cyclohexane‐d12 and Cyclohexane‐1, 1, 2, 2, 3, 3‐d6 as Studied by the Radiolysis of Water Vapor‐Cyclohexane Mixtures
Authors: Fujisaki N. , Gäumann T. 
Published: September 2012

AbstractAn attempt has been made to determine the kinetic isotope effects for the following reactions by using hydrogen atoms produced in the radiolysis of water vapor:magnified imageThe results are: kH/kD = (0.41 ± 0.05)exp(9.6 ± 0.4 kJ mol−1/RT) and kH/kD = (0.58 ± 0.06)exp(8.3 ± 0.4 kJ mol−1/RT), respectively, over the temperature range 353 K to 493 K; the errors correspond to standard deviations. The kinetic isotope effect has also been examined as a function of the ratios of c‐C6D12/c‐C6H12, total dose, total pressure and the total concentration of added cyclohexanes. Theoretical interpretation of the kinetic isotope effect has been made using the Bond‐Energy‐Bond‐Order (BEBO) method. Agreement between theoretical and experimental values is not satisfactory, even though the tunneling effect has been taken into account.
Atomabsorptionsmessungen zur Kinetik der Reaktion CH4 + O → CH3 + OH im Temperaturbereich 1500 ≤ T ≤ 2250 K
Authors: Roth P. , Just Th. 
Published: September 2012

AbstractDurch direkte Messung des zeitlichen Verlaufes der O‐Atomkonzentration in der Reaktionszone hinter Stoßwellen konnte in Gemischen aus Argon mit geringen Konzentrationen an CH4 (10 ÷ 25 ppm) und N2O (5 ÷ 150 ppm) die Geschwindigkeitskonstante der Reaktion CH4 + O → CH3 + OH

in einem Temperaturbereich 1500 ≤ T ≤ 2250 K bestimmt werden. Die Gesamtdichte, bei der die Versuche ausgeführt wurden, lag bei 7 · 1010 cm−1.
Investigation of the Mass Transfer through Turbulent Boundary Layers in Liquid‐Liquid Emulsions
Authors: Dworak R. , Wendt Hartmut 
Published: September 2012

AbstractMass transfer through turbulent hydrodynamic boundary layers of liquid‐liquid emulsions (i.e. mass transport conditions for two phase electrolysis) has been investigated by measuring diffusion limited currents in quadratic tubes with large electrodes as well as with micro‐electrodes inserted into the macro electrode. As model systems 30 vol. % emulsions of CCl4 (p = 1.6 g/cm3) and n‐hexene (p = 0.6 g/cm3) with well defined drop diameters were used. The probe system was Fe(CN)3–4‐6 dissolved in the aqueous phase. Weakly enhanced (20–30%) mass transfer—as compared with one phase flow of identical streaming velocity—was observed in the CCl4 emulsion whereas for the emulsion of the n‐hexane which possesses a remarkably lower density than the aqueous phase the same mass transfer coefficients were measured as for one phase (aqueous) flow.—The micro‐electrode measurements showed that with CCl4 the quasi‐stationary laminar sublayer is compressed somewhat but is stabilized additionally. Under the applied conditions neither droplets of a lighter phase (n‐hexane) nor of a denser phase (CCl4) are able to penetrate down to the wall. Thus in the boundary layer some sort of demixing of the emulsions is observed which is shown to be due to friction damping of the droplet movement or differences in momentum of the supporting aqueous and the dispersed organic phase resp.
Temperature Dependence of Partial Molar Volumes of Binary Critical Mixtures Study of the System Isobutyric Acid/Water
Authors: Klein H. , Woermann D. 
Published: September 2012

AbstractMeasurements of the coefficient of thermal expansion of isobutyric acid/water mixtures of critical composition and of the partial molar volumes of the two components in the critical mixtures near the critical temperature Tc show: (a) The temperature dependence of the coefficient of thermal expansion is consistent with a logarithmic singularity. (b) The same is true for the temperature derivatives (∂Vi/∂T)P.xc of the partial molar volumes of the two components of the mixture (isobutyric acid i = 1, water i = 2). (c) The singular parts of (∂V1/∂T)P.xc and (∂V2/∂T)P.xc have opposite signs. Approaching Tc(∂T)P.xc decreases and (∂V1/∂T)P.xc increases. These findings are interpreted by assuming that isobutyric acid/water mixtures of critical composition exhibit hydrophobic effects near Tc.
Reaktionen von Wasserstoffatomen mit Hydroperoxylradikalen I. Bestimmung der spezifischen Geschwindigkeitskonstanten der Reaktionskanäle
Authors: Hack W. , Gg. Wagner H. , Hoyermann K. 
Published: September 2012

AbstractDie Reaktion von Wasserstoff‐Atomen mit Hydroperoxyl‐Radikalen wurde in der Gasphase in zwei isotermen Strömungssystemen bei Drücken um 5 ± 102 [Pa] mit Helium als Trägergas bei 293 K untersucht. Die absoluten Konzentrationen von H, O und OH wurden mit der ESR gemessen. Als HO2‐Quelle diente die Reaktion: chemical structure image.Die Geschwindigkeitskonstante dieser Reaktion wird zu: k1 (293 K) = (9,0 ± 1) 10−5 [cm6/mol2 sec] gemessen. – Aus der Messung der Konzentrationszeitprofile für kurze Reaktionszeiten wurden die spezifischen Geschwindigkeitskonstanten der Reaktionskanäle chemical structure image. bestimmt. Dabei wurde ausgenutzt, da13 durch NO eine homogene Katalyse der Reaktion (2a) nach: chemical structure image.
The Thermal Unimolecular Decompositions of CH3CD2Cl, CD3CD2Cl, and CH3CHCl2
Authors: Jonas R. , Heydtmann H. 
Published: September 2012

AbstractThe thermal decompositions of the deuterated ethyl chlorides CH3CD2Cl and CD3CD2Cl and of 1,1‐dichloroethane CH3CHCl2 were studied in a static system in the pressure range of 0.1–300 Torr. With a previously published rate constant for the decomposition of ethyl chloride [1] the following kinetic isotope effects were obtained for the high pressure limit in the range 710–770 K: magnified image.The pressure dependent first order rate constants for the three reactions were compared with RRKM calculations, which used an activated complex model based on extended Hückel calculations [8].
H2‐Laser Photolysis Study of the Quenching of O2(b1g+) by H2 and D2
Authors: Kohse‐Höinghaus K. , Stuhl F. 
Published: September 2012

AbstractAn H2‐laser (δ ± 160 nm) was used to form metastable O2(b1 Σg+) molecules in the photolysis of O2. Monitoring the decay of the O2(b1 Σg+ → X3Σc−) emission in the presence of H2 and D2 yields rate constants of k(H2) = (8.3 ± 1.2) ± 10−13 and of k(D2) = (1.4 ± 0.2) ± 10−14 cm3 s−1 for the respective quenching process at 298 K. Preliminary results indicate similar temperature dependences (approximately 6.2 kJ mol−1 activation energy) for both reactions.
Theory of Micelle Formation Kinetics
Authors: Aniansson E. A. G. 
Published: September 2012

AbstractA survey is given of a kinetic theory for micelle formation and disintegration at small deviations from equilibrium guided by a concept of a diffusionlike flow along an aggregation number axis. Two well separated relaxation times for the monomer concentration are predicted, the short one pertaining to the rearrangement of the micellar distribution at a constant number of micelles and the long one pertaining to the change in the number of micelles with a concomitant shift in the position of the mean aggregation number of the micelles. – A “reverse” case is shown to give a relaxation time distribution at complete variance with experimental results, general conditions are given for the occurrence of only one relaxation time in the rearrangement process, and the movements of the micellar distribution at moderate and large dilutions are described. – Finally a theoretical calculation of the disintegration rate constants is presented, its extension to the dynamics of partial exits of the amphiphilic molecules is sketched, and its inferences for monolayer and bilayer structures are pointed out.
The Dynamics of Micelle Formation
Authors: Hoffman H. 
Published: September 2012

AbstractThe article presents kinetic data on micellar systems that were obtained with relaxation techniques. Problems that are relevant to the following topics are discussed in detail:

Differences in the dynamic behaviour of micellar systems consisting of single‐ and double chain detergents.
The dynamics of micellar systems consisting of ionic detergents with hydrophobic counterions.
The dynamic behavior of micellar systems of perfluorated ionic detergents.
For most of the systems two relaxation times could be observed which very often showed characteristic differences in their temperature and concentration dependence. The two relaxation processes were associated according to the theory of micelle formation by G. Aniansson and S. Wall to the shift of the micellar distribution curve and the change of the micelle concentration. The following parameters were evaluated from the data: The residence times of the detergent molecules inside the micelles, the mean aggregation number of the micelles, the width of the micellar distribution curves and the concentrations of the micellar nuclei and their aggregation numbers.
A Numerical Computation of the Diffuse Double Layer and its Application to Spherical Colloidal Particles
Authors: Diekmann Stephan , Frahm Jens 
Published: September 2012

AbstractA numerical method is presented which allows the computation of local ion concentrations as a function of distance from a charged surface. This has been applied to a micelle‐supported metal complexation reaction. The reactivity profile can be explained in the total range of surfactant concentration by making use of two different models of poly‐electrolyte solutions.
Reaktionen von Wasserstoffatomen mit Hydroperoxylradikalen II. Bestimmung der Geschwindigkeitskonstanten der Bruttoreaktion
Authors: Hack W. , Preuss A. W. , Wagner H. Gg. , Hoyermann K. 
Published: September 2012

AbstractDie Reaktion von H‐Atomen mit Hydroperoxylradikalen wurde in zwei isothermen Strömungssystemen untersucht. Der Nachweis der HO2‐ und OH‐Radikale erfolgte mit der Methode der Laser‐Magnetischen‐Resonanz. Die HO2‐Radikale warden entweder in der Reaktion H + O2 + M → HO2 + M (Strömungssystem (A)) oder in der Reaktion F + H2O2 → HO2 + HF (Strömungssystem (B)) erzeugt. Das Trägergas war Helium bei einem Gesamtdruck von 500–800 Pa(A)bzw. 130 Pa(B). ‐ Die Geschwindigkeitskonstante k2 = k2a + k2b + k2c der Gesamtreaktion: magnified image ergibt sich einmal aus der Messung der quasistationären [HO2]‐Konzentration (A) und zum anderen direkt aus der Messung des [HO2]‐Konzentrations‐Zeit‐Profils in An‐ und Abwesenheit eines H‐Atomüberschusses (B). Der Wert der Geschwindigkeitskonstante beträgt: magnified image Simulationen der [OH]‐ und [HO2]‐Konzentrationsprofile in dem System H + O2 + M bestätigen den gemessenen Wert für die Geschwindigkeitskonstante k2.
Transport Through Polymer Membranes from the Liquid Phase
Authors: Meares Patrick 
Published: September 2012

AbstractTransport from the liquid phase through homogeneous polymeric membranes has several features that distinguish it from gas and vapour permeation. The concentration of permeant in the polymer is usually high and has a large influence on diffusion coefficients. The driving force for transport, the gradient of chemical potential of the liquid, may be controlled by the application of a pressure but the functional form of the dependence of chemical potential on pressure is different in a liquid from that which applies in gas diffusion. Frequently the chemical potential gradients in liquid transport are small. ‐ The driving force may also be controlled by varying the composition of the liquid phases i. e. by setting up an osmotic pressure difference across the membrane. This can only be done with systems of more than one component and the study of transport from the liquid phase therefore leads readily into the study of several simultaneous fluxes and the possibilities of membrane selectivity and separation. ‐ This paper reviews work on the mechanisms of steady flow of, principally, organic liquids through polymer membranes under pressure from the liquid phase into either another liquid phase, as in hyperfiltration, or into a vapour phase as in pervaporation. The transport of a single liquid is considered first Then the flow of binary liquid mixtures is discussed and the mechanisms of separations or organic liquids by hyperfiltration and pervaporation are examined.
7Li and 23Na Nuclear Magnetic Relaxation in Poly(acrylic Acid) Solutions Containing a Paramagnetic Mn(II) Salt
Authors: Westra S. W. T. , Leyte J. C. 
Published: September 2012

AbstractLarge enhancements are observed for the 7Li and 23Na relaxation in solutions of poly(acrylic acid), containing Mn(II). The effect is explained by the evaluation of the increased metal ion concentrations near the polyion. — Using the cell model for polyelectrolyte solutions and the Poisson‐Boltzmann equation to obtain the distribution of the mobile ions with respect to the polymer, the calculated magnitudes of the enhancements and the dependences of the relaxation rates on the polymer charge density are found to be in agreement with the experimental data. — The condensation concept and other current two‐phase models are shown to be inadequate to account for the observed enhancements.
Magnetische Eigenschaften der Thuliumverbindungen Cs2MTmF6 (M = Na, K, Rb) und Cs2KTmX6 (X = Cl, Br)
Authors: Urland W. 
Published: September 2012

AbstractDas magnetische Verhalten von Cs2NaTmF6, Cs2KTmF6, Cs2RbTmF6 Cs2KTmCl6 und Cs2KTmBr6 wird im Temperaturbereich von 2, 9 bis 251, 3 K untersucht. Die magnetischen Daten werden mit einem früher entwickelten Modell interpretiert, bei dem der Einfluß des Kristallfeldes theoretisch durch das Angular‐Overlap‐Modell beschrieben ist. Die erhaltenen Werte des Angular‐Overlap‐Parameters eσ (R) für die einzelnen Verbindungen werden untereinander verglichen und diskutiert Die Energiewerte der Kristallfeldniveaus des 3H6‐Grundzustandes werden berechnet.
Neue Ergebnisse zur chromatographischen Trennung und Anreicherung aller Seltenen Erden
Authors: Jung K. , Weuster W. , Specker H. 
Published: September 2012

AbstractAlle Seltenen Erden können mit dem Laufmittel Diethylether/Bis‐(2‐ethylhexyl)phosphat/Salpetersäure (100:2:3,5) dünnschichtchromatographisch getrennt werden. Zweidimensional ist auch im Verhältnis 8000:1 eines Lanthanids zu allen anderen eine quantitative Trennung möglich. Als Anreicherung aus einer Uranmatrix gelingt eine Trennung Uran:SE im Verhältnis 109:1. Mittels Hochdruckflüssigkeits‐chromatographie lassen sich mit dem Laufmittel Di‐iso‐propylether/Tetrahydrofuran/Salpetersäure ohne Schwierigkeit 11 Lanthaniden, durch weitere Variation der Laufmittel (während der Elution) alle 14 Lanthaniden trennen, wie Vorversuche zeigen.