bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polarized Absorption and Photoelectron Spectra of Aceheptylene, 3.5‐Dimethylaceheptylene and 3,5,8,10‐Tetramethylaceheptylene
Authors: Bischof Peter , Gleiter Rolf , Hafner Klaus , Kobayashi Michio , Spanget‐Larsen Jens 
Published: September 2012

AbstractUV‐visible polarized absorption spectra of aceheptylene (1), 3,5‐dimethylaceheptylene (2) and 3,5,8,10‐tetramethylaceheptylene (3) have been measured at 77 K in stretched polyethylene sheets. PPP‐CI calculations of transition energies, oscillator strengths and polarization directions are in good agreement with the first ten transitions.In the photoelectron spectra of 1, 2 and 3 the first four bands could be assigned to π orbitals on the basis of semiempirical calculations. The energy level scheme and the polarization of the transitions of 1 can be understood in terms of a HMO interaction diagram between heptalene and ethylene.
Ageing Effects in Monomolecular Oxide Layers on Gold
Authors: Schultze J. W. , Lohrengel M. M. 
Published: September 2012

AbstractAgeing effects in monomolecular oxide layers on gold electrodes were investigated by fast potentiostatic pulse techniques.Oxide layers of various coverages were formed at a potential Ep within 1 ms and aged at a potential εp for ageing times between 1 ms and 1000s. Finally, the oxide was reduced potentiodynamically with 500 V s−1.With increasing ageing the reduction peaks show an increasing current and a decreasing half width. At low coverages, formed at low potentials εp, the vanishing of an unstable species and the growth of a stable oxide can be separated. At larger coverages, the increasing homogeneity of the layer can be observed only, because these effects are smeared out. Variations of εa, show that the ageing process depends on the potential. A mechanism is discussed which includes the cathodic reduction of the unstable species and the anodic formation of the stable oxide. The unstable species is probably O2‐ or OH− adsorbed reversibly.
Der Einfluß des Partialdruckes auf die Geschwindigkeit der kathodischen Sauerstoffreduktion
Authors: Fabjan Ch. , Azizian M. 
Published: September 2012

AbstractDer Einfluß des Partialdruckes auf die Geschwindigkeit der kathodischen Sauerstoffreduktion wurde an blankem Platin in saurem und alkalischem Elektrolyten und an Graphit in alkalischer Lösung untersucht. An Platin wird in beiden Fällen eine kathodische Reaktionsordnung von +1,0 ermittelt, während an Graphit ein Wert von +0,5 gefunden wird. Dieses Ergebnis erlaubt eine Formulierung des Reaktionsmechanismus in der Weise, daß an Platin die Reduktion des molekularen Sauerstoffes im Durchtrittsbereich direkt zu Wasser bzw. OH−‐Ionen führt, wobei kein Wasserstoffperoxid als stabiles Reaktionsprodukt entsteht:Für alkalische Elektrolyte:magnified imageAn Kohlematerial (Graphit) führt die Reaktion in alkalischem Medium ausschließlich zur Bildung von Peroxid.
Die Reaktion von F‐Atomen mit HCl
Authors: Wagner H. Gg. , Warnatz J. , Zetzsch C. 
Published: September 2012

AbstractDie Temperaturabhängigkeit der Geschwindigkeitskonstanten der schnellen Reaktion

wird in einem Strömungssystem mit massenspektrometrischer Analyse gemessen. Als Ergebnis erhält man

zwischen 250 K und 370 K.
Magnetische Resonanzuntersuchungen zur Struktur, Kinetik und Hyperfeinwechselwirkung des Systems Nitroxidradikal‐Wasser
Authors: Meise Karin , Müller‐Warmuth W. , Nientiedt H.‐W. 
Published: September 2012

AbstractWäßrige Lösungen von drei verschiedenen organischen freien Nitroxidradikalen wurden zwischen 0 und 100°C mit magnetischen Resonanzmethoden untersucht. Messungen der Protonenrelaxationsraten zwischen 0,75 und 60 MHz lieferten Aussagen über die zwischenmolekularen Wechselwirkungen. Aus der dynamischen Kernpolarisation im schwachen Magnetfeld konnte auf die dipolaren und skalaren Relaxationsanteile geschlossen werden. Weiter wurden chemische Kontaktverschiebungen der Protonen bei 270 MHz beobachtet, um in Kombination mit den anderen Daten die Bildungskonstanten des Komplexes Nitroxid‐Wasser und die Hyperfeinkopplungskonstante über die Wasserstoffbrücke zu ermitteln. Detaillierte Angaben werden über die Lage des Gleichgewichtes, die Lebensdauer der Wasserstoffbrücke, und die einzelnen Bewegungsprozesse gemacht.
The Solvolysis of Tetranitromethane in Various Polar and Nonpolar Solvents
Authors: Frank A. J. , Henglein A. 
Published: September 2012

AbstractTetranitromethane yields nitroform upon its thermal decomposition in water, alcohols, acetone and n‐hexane. The rate constant of nitroform formation was determined by measuring the absorbance of the nitroform anion C(NO2)3− as a function of reaction time. The decomposition in water proceeds with an activation energy of 1.6 eV and an Arrhenius factor of 1017.8 s−1 which is of similar magnitude to that obtained in the gas phase thermolysis of tetranitromethane. Two mechanisms involving heterolytic CN bond rupture in water and homolytic CN bond cleavage in the less polar solvents are proposed to account for the solvolysis reactions. In the latter case, this leads to the formation of the trinitromethyl radical C(NO2)3, which, because of its unusually high electron affinity, is able to abstract an electron from the alcohols and acetone; in n‐hexane, the main reaction path involves hydrogen atom abstraction by the radical. Above pH 6 in aqueous solution, the rate of hydrolysis is markedly catalyzed by OH− anions.
A Proton Magnetic Resonance Study of Ionic Association in Aqueous and Nonaqueous Solutions of Tetraalkylammonium Salts
Authors: Kabisch G. 
Published: September 2012

AbstractThe behaviour of the alkyl proton resonances of symmetrical tetraalkylammonium ions is studied in aqueous and nonaqueous salt solutions. Information about ion‐pairing can be obtained by investigating the relative chemical shift Δδ = δCH2(1) ‐ δCH3 of the cationic protons as a function of concentration, temperature, and anion. In organic solvents cation‐anion association is evident from our experimental data. The corresponding equilibrium constants could be determined for several TAA salts in acetonitrile solution. In aqueous solution the association behaviour is a more complex one. It seems that at low and medium concentrations cation‐cation interactions are dominant, whereas in concentrated solutions multiple ion aggregates involving anions are formed.
Pressure Dependence of the Selfassociation of 9‐Methylpurine in Aqueous Solution
Authors: Gaarz U. , Lüdemann H.‐D. 
Published: September 2012

AbstractThe selfassociation of 9‐methylpurine (9‐MP) in aqueous solution has been studied by analysis of the proton chemical shift concentration dependence at pressures up to 1500 bar. To this purpose a high pressure glass cell has been developed, fitting into the standard receiver coil of a high resolution NMR spectrometer. The influence of pressure on the UV‐spectra of 9‐MP has been measured. Pressure favours self association of 9‐MP. The thermodynamic data derived from an isodesmic association model are:K (1 bar, 20°C) = 1.4 mol−1; K (1500 bar, 20°C) = 1.8 mol−1; ΔH (van't Hoff) = ‐(9.6 ± 1)kj·mol−1 and ΔV = ‐(4.0 ± 1.0)cm3 · mol−1.
Transport Properties of Nine Binary and Two Ternary Mixtures of Gases at Low Density
Authors: Kestin J. , Ro Sung Tack 
Published: September 2012

AbstractThe paper analyses earlier data on the viscosity of binary and ternary mixtures in terms of the extended law of corresponding states due to Kestin, Ro, and Wakeham (KRW). The binary mixtures involve CO2 and CH4 with each other, and each with He, Ne, Ar, N2. The ternary mixtures are: N2ArCO2 and CH4N2CO2.Measurements fully corroborate the efficiency of the KRW law for the calculation of viscosity and binary diffusion coefficient of the simpler polyatomic gases, as expected from theory.The paper contains short tables of the viscosity and binary diffusion coefficients for the nine binary systems under consideration.
Zur Bestimmung der Beweglichkeit von Kohlenwasserstoffmolekülen auf Katalysatoroberflächen mittels Neutronenstreuung
Authors: Stockmeyer R. 
Published: September 2012

AbstractDie Intensitätsverteilung von langsamen Neutronen, die an adsorbierten Kohlenwasserstoffmolekülen gestreut worden sind, enthält Informationen über die Bewegung der Moleküle. Hier wird das Streugesetz für inkohärent streuende Moleküle unter Berücksichtigung der sehr verschiedenen Beweglichkeit senkrecht und parallel zur Oberfläche abgeleitet. Im Gegensatz zu dem bekannten Streugesetz von dreidimensional diffundierenden Teilchen divergiert das Streugesetz für zweidimensional diffundierende Moleküle logarithmisch für verschwindenden Energieübertrag. Die sich daraus ergebenden Konsequenzen für die Interpretation von Neutronenstreudaten werden diskutiert.
Spektroskopische Untersuchungen an Merocyaninen II. Blitzspektroskopische Untersuchung der thermischen cis → trans‐Isomerisierung der malodinitril‐substituierten vinylogen Säureamide
Authors: Joerges Eike , Schneider Siegfried , Dörr Friedrich , Daltrozzo Ewald 
Published: September 2012

AbstractOffenkettige Merocyanine zeigen eine photoinduzierte trans → cis‐Umlagerung, der eine thermische cis → trans‐Rückumwandlung folgt. In dieser Arbeit wird die thermische cis → trans‐Isomerisierung der malodinitril‐substituierten vinylogen Säureamide blitzphotometrisch als Funktion von Temperatur und Lösungsmittel untersucht. Die Abhängigkeit der Aktivierungsparameter von der Polarität des Lösungsmittels und der Länge der Merocyanine wird anhand quantenmechanischer Modellrechnungen diskutiert.
Near Infrared Absorption of Ethylene between 5500 cm−1 and 6500 cm−1 to High Pressures and Temperatures
Authors: Buback M. , Nees F. W. 
Published: September 2012

AbstractThe near infrared absorption of pure ethylene in the region of the first overtones of the CH stretching fundamentals (5500 cm−1 to 6500 cm−1) was measured at supercritical temperatures (Tc = 9.5°C) between 22°C and 200°C from 0.05 to 3000 bar.Density and temperature dependence of bandshape, maximum frequency and absorption intensity are reported. The bands observed within a wide range of experimental conditions are assigned to combinations and overtones of vibrations. At high densities pressure induced (“forbidden”) bands occur.The molar integrated absorption intensity of the strong ν5 + ν9 combination band at 6138 cm−1 is independent of pressure and temperature. This enables spectroscopic concentration determinations on ethylene in high pressure‐high temperature equilibria and reactions.
Entmischungserscheinungen in Pd  B‐Legierungen
Authors: Brodowsky H. , Schaller H.‐J. 
Published: September 2012

AbstractUnterhalb einer kritischen Temperatur von 410°C existiert in der festen Lösung von Bor in Palladium eine Mischungslücke, deren Grenzzusammensetzungen bei 312°C röntgenographisch zu PdB0,021 und PdB0,114 ermittelt wurden. Die Mischungslücke ergibt sich in guter Näherung durch die Auswertung eigener Aktivitätsmessungen bei 1000°C; dabei wurden die Überschußpotentiale des Bors analog wie diejenigen des Wasserstoffs im Palladium durch zwei Effekte gedeutet: Durch den Anstieg der Fermi‐Energie beim Übertritt der äußeren Bor‐Elektronen in das Elektronengas des Metalls sowie durch eine Attraktionswechselwirkung der Zwischengitteratome, die durch die Gitterverzerrung hervorgerufen wird.
Keimbildung und Kristallwachstum bei der elektrolytischen Abscheidung von Kupfer‐Zink‐Legierungen
Authors: Randig H.‐J. , Lacmann R. 
Published: September 2012

AbstractEs werden experimentelle Untersuchungen der elektrolytischen Abscheidung von Kupfer‐Zink‐Legierungen auf Platineinkristallkathoden beschrieben. Der Kupfergehalt der Legierungen, die aus cyanidischen Lösungen abgeschieden wurden, nimmt mit zunehmender Überspannung zunächst ab, durchläuft ein Minimum und steigt dann wieder an. In einigen Fällen treten in den Kurven Stufen auf, die dem Übergang zwischen den Messingphasen entsprechen. Die Kupfer‐ und Zinkteilstromstärken streben im Gebiet des Minimums des Kupfergehaltes Grenzwerten zu.Die Meßergebnisse können theoretisch mit Keimbildungsvorgängen erklärt werden, die bei hoher Stromdichte zusätzlich durch vorgelagerte chemische Reaktionen gehemmt werden.
Thermodynamic Properties and Structure of Liquid Alloys
Authors: Predel Bruno 
Published: September 2012

AbstractThe direct correlation between the atomic structure of liquid alloys and their thermodynamic properties makes it possible in principle to obtain information about the structure changes that occur as a result of alloy formation. It is first shown that in addition to the change of the bond properties atomic volume differences of the alloy partners have a definite influence on the energetics of alloy formation. Furthermore a model is developed which successfully explains the deviations from regular behavior of some alloy systems with tendencies toward compound formation by postulating the existence of regions with special coordination relationships in the melt which are in a dynamic equilibrium with statistically disordered regions. Finally, it is suggested that the tendencies of some alloys to form metastable glass like phases are related to the tendencies of these alloys toward the prevailing formation of bonds between atoms of the different species.
Measurement of the Structure Factor of Liquid Rubidium by Neutron Diffraction up to 1400 K and 200 bar
Authors: Block R. , Suck J. B. , Gläser W. , Freyland W. , Hensel F. 
Published: September 2012

AbstractThe structure factor S(Q) of liquid rubidium has been measured by neutron diffraction in the temperature range between 450 K and 1400 K corresponding to a density change from 1.42g/cm3 to 0.98 g/cm3. Measurements have been performed with a diffractometer for elastic diffuse scattering of neutrons at the high flux reactor in Grenoble. To avoid evaporation of the liquid metal at high temperatures; a new technique had to be developed. A detailed description is given of the experimental set‐up which is suitable for neutron diffraction measurements of corrosive liquids at elevated temperatures and pressures. It is the first time that neutron diffraction measurements on a liquid metal have been extended to these combined conditions of high temperature–high pressure, as are reported in this paper.The momentum transfer Q covered in this investigation ranges from 0.2 Å−1 to 2.4 Å−1. As a function of temperature and density the following significant changes in S(Q) have been observed:
the height of the first maximum decreases from about 2.0 at 450 K to 1.12 at 1400 K;
in the same temperature limits S(Q) at the lowest Q‐values measured increases by a factor of 6;
a clear shift in the position of the first maximum from 1.525 Å−1 to 1.43 Å−1 is found.
Up to 1200 K three different pressures, saturation pressure, 100 bar, and 200 bar have been studied. Corresponding to the relatively small compressibility of liquid rubidium at these temperatures, no appreciable pressure dependence of S(Q) at the different constant temperatures was observed. The accuracy of the measured structure factor data is chequed at low Q‐values by a comparison of compressibilities of liquid rubidium determined from recent density measurements with those extracted from our S(Q)‐values according to the Ornstein‐Zernike relation.
Untersuchungen zum Halbleiter‐Metall‐Übergang von Schmelzen im System Ge As Te. I. Elektrische Leitfähigkeit
Authors: Schnurnberger W. , Thurn H. , Krebs H. 
Published: September 2012

AbstractDie elektrische Leitfähigkeit von Schmelzen der binären Systeme Ge  Te und AsTe sowie der ternären Schnitte Ge5AsxTe95‐x und Ge15AsxTeg85‐x wurde mit einer verbesserten elektrodenlosen Meßmethode bis 1000°C untersucht. Alle Schmelzen zeigen bei hohen Temperaturen ein sehr ähnliches, nahezu metallisches Verhalten. Mit abnehmender Temperatur erfolgt ein Übergang zu halbleitendem Verhalten, der bei glasig erstarrenden Proben besonders ausgeprägt ist. Dieser Übergang ist eine Folge der Änderung des Bindungssystems und damit der Nahordnung der Atome in der Schmelze. Die dadurch bewirkte Änderung der Bandstruktur führt zu besonders hohen Werten der Aktivierungsenergie des elektrischen Widerstandes im Übergangsgebiet.
Catalysis on Liquids Metals
Authors: Schwab Georg‐Maria 
Published: September 2012

AbstractThe rate and activation energy of formic acid dehydrogenation over liquid metals, especially mercury, tin and thallium and their alloys, are studied. The results suggest that beside the usual electronic effects covalent bonds and Friedel‐terms may occur in liquid alloys. The validity of the compensation effect for a reaction catalysed by these alloys shows that also in solid catalysts this effect is not necessarily a consequence of the presence of “active centers”.
Stability Function of Antimony‐Chalcogen Melts
Authors: Blachnik R. , Bolte G. 
Published: September 2012

AbstractThe activities of chalcogen were determined in molten mixtures of antimony‐sulphur and antimony‐tellurium by a modified dew‐point method. These data and literature data were used to derive the stability function δ2ΔG/δx2 which indicates the formation of associates at a composition of 60 atom per cent chalcogen in the liquid state. These associates with polymeric bonding systems are of different structure and bonding strength and thus influence the topology of the Vb‐Vlb phase diagrams.
Electrical Conductivity and Thermopower of Metal Ammonia Solutions
Authors: Hahne S. , Krebs P. , Schindewolf U. 
Published: September 2012

AbstractData of equivalent conductivity of sodium ammonia solutions in a wide concentration, temperature and pressure range prove that the nonmetal‐metal transition is favoured by increasing temperature and disfavoured by increasing pressure. Some data on the temperature dependence of the thermopower support the concept of activated transport (semiconduction) in the transition range, although the combination of thermopower and conductivity data does not follow the simple theory of semiconductors. In conclusion it is shown that the conductivity behaviour of metal ammonia solutions can be explained by a homogeneous chemical equilibrium between solvated electrons (electrolytic conduction) and free electrons (metallic conduction) which as usually depends on concentration, temperature and pressure.
Ionic Conductance in Liquid Cesium Gold Alloys
Authors: Krüger K. D. , Schmutzler R. W. 
Published: September 2012

AbstractThe paper presents experimental data of the electromigration in liquid Cs‐Au alloys at the stoichiometric composition. The experiments were performed at 65°C, i.e. about 60°C above the melting point of the compound, with a modified capillary technique. A simple model allows to evaluate the correlation of current induced atom or ion transport to the total charge transported through the specimen. It is found that one Cs‐ion is transported per elementary charge into the cathode compartment within experimental error of about ± 25%, which is exactly the value required by the Faraday law of electrolyses in ionic conductors. It is therefore concluded, that the stoichiometric liquid CsAu alloy consists essentially of Cs+ and Au− ions.
Concentration Fluctuations in Solutions of Potassium in Potassium Bromide. A Neutron Small Angle Scattering Investigation in the Non Metal to Metal Concentration Range
Authors: Jal J. F. , Chieux P. , Dupuy J. 
Published: September 2012

AbstractA preliminary study of the concentration fluctuations in solutions of K in KBr has been performed by small angle neutron scattering in the non metal to metal transition concentration range. Approximate values of the correlation length of these fluctuations and their temperature dependence have been obtained at the critical concentration of the liquid‐liquid immiscibility gap. These fluctuations are observed everywhere above the immiscibility gap.
A Dipole Model for the Outer Solvation Sphere and its Application to Outer Sphere Electron Transfer Reactions
Authors: Schmickler Wolfgang 
Published: September 2012

AbstractThe outer solvation sphere of an ion partaking in an outer sphere electron transfer reaction is viewed as an ensemble of polarizable dipoles. The formalism of Mandel and Mazur is used to derive expressions for the generating function and the energy of reorganization in terms of averages over molecular quantities. On passing to the continuum representation the results are shown to be equivalent to the theories of Marcus and Hush. The relation of the present work to the polaron model and to the work of Bockris and Sen are also discussed.
The Association of 3‐ethylpentanol‐3 in Carbon Tetrachloride from the Static Dielectric Permittivity and the Infrared Absorbance
Authors: Kunst M. , van Duijn D. , Bordewijk P. 
Published: September 2012

AbstractStatic dielectric constants and Infrared absorbances in the hydroxyl stretching range have been determined for solutions of 3‐ethylpentanol‐3 in carbon tetrachloride with molar fractions between 0.001 and 0.1 at temperatures between 15°C and 45°C.The measurements favour the interpretation of the association of this alcohol by a monomer‐dimer‐tetramer equilibrium with heats of association of dimer and tetramer of 20 and 65 kJ/mol respectively. It appears that in a restricted concentration range this model is applicable to measurements of other alcohols in apolar solvents in the literature, and the model was used to calculate equilibrium constants and heats of association of these alcohols.
Reaktionen von Molekülen in definierten Schwingungszuständen (III), die Reaktion von HCl(ν) mit H‐, D‐, Cl‐ und Br‐Atomen
Authors: Arnoldi D. , Wolfrum J. 
Published: September 2012

AbstractDer Einfluß einer selektiven Schwingungsanregung auf den Ablauf einfacher neutraler und endoenergetischer Reaktionen in der Gasphase wurde anhand der Reaktionen von HCl(ν) mit H‐, D‐, Cl‐ und Br‐Atomen mit Hilfe der Methode der laserinduzierten Fluoreszenz in einer Strömungsanordnung untersucht. Durch die Bestimmung der absoluten Konzentration der schwingungsangeregten Moleküle, die zeit‐aufgelöste Beobachtung der Atomkonzentration und den massenspektrometrischen Nachweis der Produkte der laserinduzierten Reaktionen über ein Molekularstrahl‐Probenahmesystem war eine direkte Unterscheidung zwischen reaktiven und energieübertragenden Prozessen möglich.Bei einer Laserimpulsenergie von 10 mJ ergibt sich aus dem Vergleich der Intensität der Infrarotfluoreszenz der Zustände HCl(ν = 2) und HCl(r = 1) ein Anregungsgrad vonmagnified imageDieses Ergebnis erhält man auch aus der Messung des Temperaturanstieges von ΔT = 7 K in der Reaktionsmischung nach vollständiger Schwingungsrelaxation von HCl(ν) durch Chloratome.Die Messungen der spezifischen Geschwindigkeitskonstanten k(ν = 1) wurden bei sehr geringem Anregungsgrad ausgeführt. Hierdurch konnte eine Entvölkerung des Zustandes HCl(ν = 1) auf dem Weg über höhere Schwingungszustände vermieden werden. Im einzelnen wurden bei 295 K folgende Ergebnisse erhalten:magnified imageDer drastische Anstieg der Geschwindigkeit der Reaktion (5) um einen Faktor 1011 nach Schwingungsanregung von HCl(ν) erlaubte eine isotopenselektive Reaktionsführung der Artmagnified imageDie gebildeten BrCl‐Moleküle zeigen eine Anreicherung auf 90% Br35Cl.
Rate Measurements for the Reaction H + Cl2 → HCl + Cl by Lyman‐α Fluorescence
Authors: Wagner H. Gg. , Welzbacher U. , Zellner R. 
Published: September 2012

AbstractThe rate of the reaction between hydrogen atoms and chlorine has been determined in a discharge‐flow system. By use of sensitive detection of H atoms by Lyman‐α resonance fluorescence the reaction could be studied at low initial H atom concentrations and unperturbed by interfering processes. From measurements in the temperature range T = 252–458 K the Arrhenius expression
Rate Constant for the Reaction of OH with N2O at 298 K
Authors: Biermann H. W. , Zetzsch C. , Stuhl F. 
Published: September 2012

AbstractA value of k1 = (3.8 ± 1.2) · 10−17 cm3 molecule−1 s−1 for the rate constant of the reaction of OH radicals with N2O was determined at 298 K. For these experiments OH was generated by flash photolysing mixtures of H2O and N2O and was monitored by resonance absorption using a path length of 560 cm. The results are discussed with regard to the atmospheric residence time of N2O.