bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoacoustic Study of Vibrational Relaxation of NO
Authors: Koshi M. , Koseki K. , Matsui H. 
Published: July 2012

AbstractThe first vibrational level of NO diluted in He is excited by the mechanically chopped CO laser beam and the relaxation rate constant is determined by analysing the phase shift of the acoustic signals at a temperature range of 235 – 294 K. Additional measurements in a shock tube have been done to cover the higher temperature range of 700–1900 K. The present results agree very well with those of previous work. The transition probability of vibrational energy transfer of NO to He can be expressed by

The short‐range repulsive collision model is found to represent the present experimental results of the NOHe system.
Kinetic Studies of NH2 and HCO Reactions with Unsaturated Hydrocarbons, by Flash Photolysis and Laser Resonance Absorption
Authors: Lesclaux R. , Veyret B. , Roussel P. 
Published: July 2012

AbstractThe flash photolysis and laser resonance absorption technique was used for the determination of the rate constants of reactions of NH2 with acetylene in the temperature range 340–510 K, NH2 with 1,3‐butadiene from 298 to 500 K and HCO with 1,3‐butadiene from 298 to 522 K. The Arrhenius expressions for the rate constants are the following (in cm3 · molecule−1 · s−1 units):

The rate expressions for k1, and k2 are compared to previous results reported in the literature. The determination of k4 represents the first data concerning the reactivity of HCO with an unsaturated hydrocarbon. A tentative evaluation of the reactivity of HCO with olefins is also given. Product analysis shows that reaction (4) proceeds essentially via an addition process rather than a hydrogen atom transfer from HCO.
Thermodynamic Properties of Molten Sodium‐Lead Alloys: EMF Measurements and Interpretation
Authors: Saboungi Marie‐Louise , Herron Steven J. , Kumar Romesh 
Published: July 2012

AbstractChemical potentials of Na as a function of composition in liquid NaPb alloys were determined in the temperature range 380–480°C by an emf technique. A solid β‐Al2O3 electrolyte and a coulometric titration were used to vary the composition. The variations of the logarithm of the activity coefficient of Na with composition exhibit three inflection points, at XNa ˜ 0.5, 0.66, and 0.80. The inflections at 0.5 and 0.80 correspond to maxima, and the inflection at 0.66 corresponds to a minimum in the Darken excess stability function. The entropy, excess stability, and other related functions, evaluated across the entire composition range, reflect the unusual properties of liquid NaPb solutions. A possible interpretation of these features might be related to the simultaneous presence of more than one valence states of Pb.
The Effect of Ionic Strength and Pressure on the Complex Formation and Hydrolysis Equilibria in the Aquated Iron(III)‐Thiocyanate System
Authors: Martinez P. , van Eldik R. 
Published: July 2012

AbstractThe equilibrium constants for the complex formation of Fe(H2O)3+6 with SCN− (K1) and the hydrolysis of Fe(H2O)5SCN2+ to produce Fe(H2O)4(OH)SCN+ (K4) were studied as a function of ionic strength (0.1 to 1.5 M) at 25°C and pressures up to 120 MPa. The ionic strength dependencies at ambient pressure can be expressed as log K1 = 2.86 ‐ 3.05 √ μ (1 + 2.96 √ μ)−1 + 0.04 μ and log K4 = ‐0.93 ‐ 1.02 √ μ (1 + 1.97 √ μ)−1 + 0.06 μ, from which the distance of closest approach follows to be 0.9 and 0.6 nm, respectively. The pressure dependencies of K1 and K4 result in reaction volumes ranging from 10.0 to 7.5 and 11.9 to 11.0 cm3 mol−1, respectively, for zero to 1.5 M ionic strength. These data combined with those for the hydrolysis of Fe(H2O)3+6 reported before, enable the estimation of the equilibrium constant (K3) for the formation of Fe(H2O)4(OH)SCN+ from Fe(H2O)5OH2+ and SCN−, as a function of ionic strength and pressure. This is the first study to report such data for K3, and K4, and the results are discussed in reference to data for the overall system.
Efficient Intramolecular Fluorescence Quenching in Triphenylmethane‐Dyes Involving Excited States with Charge Separation and Twisted Conformations
Authors: Vogel Martin , Rettig Wolfgang 
Published: July 2012

AbstractThe high fluorescence quantum yields ϕf of most Triphenylmethane(TPM)‐dyes and carbon‐bridged TPM‐dyes in highly viscous solutions (ϕf ranging from 0.3 to 0.8) decrease with increasing temperature by a factor > 100, due to viscosity dependent nonradiative deactivation. The deactivation rates krd of bridged model dyes are significantly smaller (by a factor of up to 170) as compared to krd of the unbridged crystal violet. ‐ Application of the Twisted Intramolecular Charge Transfer (TICT)‐model to neutral and ionic TPM‐dyes yields an explanation for the different behaviour of similarly structured compounds. The influence of steric and electronic factors on various TPM‐dyes is discussed within this framework. This leads to a simple rule involving donor and acceptor properties of molecular subunits, which permits the prediction of fluorescence properties (high quantum efficiency for laser dyes or ultrafast deactivation for saturable absorbers).
Studies on the n‐GaAs Photoanode in Aqueous Electrolytes. 2. Differential Capacitance Behaviour
Authors: Vanmaekelbergh D. , Gomes W. P. , Cardon F. 
Published: July 2012

AbstractImpedance measurements were made on the n‐GaAs/Fe2+ photoanode as a function of electrode potential, light intensity and Fe2+ concentration. The occurrence of a peak in the parallel‐equivalent capacitance vs. potential curve indicates that surface states participate to the interfacial impedance. Considering ordinary as well as decomposition‐induced surface states and basing upon kinetic results, numerical simulations of such peaks were made for various circumstances. The calculated results are found to be in fair agreement with the experimental data.
Comparative Studies of Photoelectrochemical Behaviours of Rutile and Anatase Electrodes Prepared by OMCVD Technique
Authors: Minoura H. , Nasu M. , Takahashi Y. 
Published: July 2012

AbstractPhotoelectrochemical behaviours of two kinds of polymorphic form of TiO2, rutile and anatase, prepared by the organometallic chemical vapour deposition from isopropyl titanate have been comparatively studied. Photoelectrochemical characteristics of these TiO2 electrodes depend strongly upon the crystal structure and the deposition temperature. Their bandgap energies have been determined to be 3.0 eV and 3.2 eV, respectively, by the analysis of the photocurrent action spectra. The conduction band‐edge and the valence band‐edge of the anatase electrode, which have been estimated from photocurrent‐potential curves, locate at the energy level about 0.1 eV higher and lower, respectively, than those of the rutile electrode.
Entmischungsvorgänge in Polyvinylidenfluorid‐Polyethylacrylat‐Mischungen
Authors: Endres B. , Wendorff J. H. 
Published: July 2012

AbstractDas amorphe Polyethylacrylat und das teilkristalline Polyvinylidenfluorid sind in der Schmelze bei nicht zu hohen Temperaturen im gesamten Konzentrationsbereich der Mischung verträglich. Eine Temperaturerhöhung führt zu einer Entmischung in der Schmelze, d.h. es existiert eine untere kritische Entmischungstemperatur. Auch eine Abkühlung aus der Schmelze bewirkt eine Entmischung, die nun allerdings durch die partielle Kristallisation des PVDF gesteuert wird. Durch geeignete Temperaturführung ist es möglich, gezielt unterschiedliche Endstrukturen für die Mischungen zu erhalten, bedingt durch Variationen in den Entmischungs‐ und Reifungsmechanismen. Diese Endstrukturen nehmen Einfluß auf die beobachteten makroskopischen Eigenschaften. ‐ Wir untersuchten die Strukturausbildung infolge einer spinodalen Entmischung und der sich anschließenden Reifung. Die Reifung ist dabei kontrolliert durch einen viskosen Fluß, der durch die im System vorliegenden Grenzflächen gesteuert wird. Eine erneute Temperaturerhöhung nach einer Reifung führt zu einer Einstellung des neuen Gleichgewichtszustandes über Entmischungsprozesse, sowohl in der Matrix als auch in der dispersen Phase. Bei einer Temperaturabsenkung führt der Weg zum neuen Zustand bei einem gereiften System dagegen nicht über eine Entmischung, sondern über eine langreichweitige Interdiffusion der Komponenten über die Phasengrenzen hinweg. ‐Durch Variation der Temperatur konnte also eine gesteuerte Strukturausbildung in der Polymerlegierung induziert werden. Hierzu muß allerdings das Phasendiagramm des verwendeten Systems bekannt sein. ‐Wir verwendeten eine Methode, die direkt die Möglichkeiten der gesteuerten Phasenseparation benutzt. Hierzu werden Legierungen des Systems bei verschiedenen Temperaturen im instabilen Bereich zur Phasenseparation gebracht. Mittels kalorimetrischer Messungen ergab sich das Massenverhältnis der beiden Phasen. Durch eine Bilanzgleichung für die beiden Polymeren in den Phasen wird es möglich, die Binodale zu bestimmen. Die Spinodale wurde mittels Röntgenkleinwinkelmessungen bestimmt. Außerdem wurde die Spinodale aus den Daten, die sich mittels der DSC‐Messungen ergaben, theoretisch berechnet.
Struktur und Eigenschaften von Modellverbindungen für segmentierte Polyurethanelastomere
Authors: Eisenbach C. D. , Nefzger H. , Baumgartner M. , Günter Cl. 
Published: July 2012

AbstractUniform model compounds for the soft and hard segments of polyurethane (PU) elastomers and the corresponding tailor‐made elastomers with monodisperse segment length distribution were investigated in regard to the structure, morphology and structure‐properties relationships of thermoplastic PU elastomers. The main conclusions relevant to the hard domains are a) that the crystalline fractions consist of a conglomerate of the eutectic of the short segments in particular and mixed crystals of segments longer than three repeat units (successive lengths only), without evidence of chain folding, b) that polymorphism exists for the hard segment crystallites and in the interface region, and c) that a rapid transurethanification reaction occurs between hydrogen bond forming urethanes at elevated temperatures.
Dielectric Properties of Some Side Chain Liquid Crystalline Polymers
Authors: Haase W. , Pranoto H. , Bormuth F. J. 
Published: July 2012

AbstractAn experimental setup to determine the anisotropic dielectric constants for liquid crystalline side chain polymers as function of the temperature and the frequency in the range between 100 Hz and 10 MHz is described. From the anisotropic dielectric data some more specific informations can be obtained comparing with the results obtained from unoriented samples. ‐ The anisotropic dielectric properties of two liquid crystalline side chain polymers containing the same polyacrylic main chain and slightly modified side chains are described in the glassy, nematic as well as in the isotropic state as function of temperature and frequency. For these compounds, three different relaxation processes are described. A process was found with the main component in ϵ∥ due to the relaxation of the mesogenic side chain around the main chain back bone. A broad relaxation process, near above the glass temperature, with the main component in ϵ⟂ is interpreted as due to diffusive motion of different dipoles. Another broad relaxation process occurs in the glassy state, containing parallel and perpendicular dipole components of the mesogenic ester group. In the isotropic state, the relaxation process is dominated by the parallel relaxation in the nematic state.
Mischbarkeit und Phasenverhalten von Polymerblends
Authors: Klotz S. , Gräter H. , Cantow H.‐J. 
Published: July 2012

AbstractMeasurements of polymer‐polymer interactions by gas‐chromatography facilitate the quantitative thermodynamic description of polymer blends in terms of Flory‐Huggins and Flory equation‐of‐state interaction parameters. These parameters were found to depend on concentration and molecular weights of the components. The interaction surface including the phase diagram of poly(styrene)‐poly(vinylmethylether) is obtained. Poly(styrene)‐poly(phenyleneoxide) were investigated by gas‐chromatography too. Lower critical solution behaviour is also observed for this system. The results are discussed and compared with theoretical calculations according Flory's equation‐of‐state theory. There is only qualitative correspondence between theoretical calculations and experiments. Additionally polymer‐polymer interactions in dilute solution were investigated. The so‐called light scattering under “optical θ‐condition” make it possible to state whether a polymer pair is compatible or not.
Interpretation of Counterion Spin Relaxation in Polyelectrolyte Solutions. II. Effects of Finite Polyion Length
Authors: Halle Bertil , Bratko Dušan , Piculell Lennart 
Published: July 2012

AbstractThe applicability of the recently proposed CDM theory of counterion spin relaxation in polyelectrolyte solutions [Halle, Wennerström & Piculell, J. Phys. Chem. 88, 2482 (1984)] is extended to low degrees of polymerization. Polyion end effects on the counterion distribution and dynamics are described in the spheroidal‐cell model of Bratko & Dolar [J. Chem. Phys. 80, 5782 (1984)]. The extended theory is applied to 23Na spin relaxation data from saltfree solutions of sodium poly (styrenesulfonate) and it is found that the available data can be explained by a model in which polyions of length 20–100nm reorient as fully extended, rigid bodies.
Solid State Chemical Model for the Solubility Behaviour of Homogeneous Solid Co‐Mn‐Carbonate Mixtures
Authors: Gamsjäger H. 
Published: July 2012

AbstractA continuous series of homogeneous solid mixtures Co(1‐x)MnxCO3 was synthesized by an autoclave method. In agreement with the formalism of ideal and regular solid ionic mixtures, the excess molar volume of mixing was negligible and the cation‐anion distances obeyed Vegard's rule in the whole compositional range. Solubility measurements using the pH variation method revealed that Co(1‐x)MnxCO3 phases dissolved congruently in aqueous acidic media at 50°C. Thermodynamic analysis of the solubility data showed that a closer fit was obtained assuming regular rather than ideal mixing.
On the Order‐Disorder Phase Transition of Anilinium Halides. Crystal Structure of the High and Low Temperature Phase of Anilinium Iodide, C6H5NHI⊖ (C6D5NHI−). X‐Ray and Neutron Diffraction Studies
Authors: Fecher Gerhard , Weiss Alarich 
Published: July 2012

AbstractThe crystal structure of the high temperature phase I of anilinium iodide, C6H5NHI⊖, was determined by X‐ray and neutron diffraction at T = 294 K: D‐Pnaa, Z = 4, a = 1738.2(10) pm, b = 636.3(5) pm, c = 703.9(5) pm, ϱcalc = 1.886 Mgm−3. At Tc = 241 K, a ferroelastic phase transition occurs. The crystal structure of the low temperature phase II was studied on C6D5NHI⊖ by neutron diffraction at T = 140K: C52h‐P21/a, Z = 4, a = 1753.8(10) pm, b = 614.2(5) pm, c = 706.5(5) pm, β = 90.79(1)°, ϱcalc = 1.973 Mgm−3. Phase I is disordered with respect to four different positions of the −NH group, whereas phase II is ordered. The present results are compared with the crystal structures and the phase transition of anilinium bromide, C6H5NHBr⊖. The mechanism of the phase transition is discussed.
Vapour Pressure of Molten Acidic Potassium Chloride‐Aluminium Chloride‐Aluminium Chloride Monoammine Mixtures
Authors: Nakamura Kunihiko , Østvold Terje , Øye Harald A. 
Published: July 2012

AbstractThe acidic KCl‐AlCl3NH3AlCl3 melt has been studied by vapour pressure measurements, vapour condensation measurements and mass spectrometry. ‐ Vapour pressures were measured by the boiling point method. The total vapour pressure above AlCl3NH3(1) is given by the expression: ln(P/atm) = ‐8660 (T/K)−1 + 12.69. The partial pressure may be expressed by ln (P3/atm) ∼ ‐8589 (T/K)−1 + 12.53. ‐ Together with mass spectrometric experiments the composition of the equilibrium vapour was determined by direct condensation of the boiled‐off vapour above the KCl‐AlCl3NH3‐AlCl3 melts. The existence of the species Al2Cl6, AlCl3, AlCl3NH3 and Al2Cl6NH3 were confirmed. ‐ Thermodynamic properties of the ternary melts were described through thermodynamic model calculations based on the following equilibria.

The activities of Al2Cl6 calculated at a given temperature were in good agreement with experimental data (SD in the fit was ± 2.1%). The calculated total pressures agreed fairly well with experimental pressures (SD = ± 8.5%) taking also into account data which was not used for modelling.
Proton Exchange of Water in Layered Intercalation Compounds
Authors: Wein E. , Müller‐Warmuth W. , Schoöllhorn R. 
Published: July 2012

AbstractProton exchange of water has been studied in hydrated layered dichalcogenides of the type Ax(H2O)y[NbS2] by NMR techniques. Intermolecular proton exchange has been detected in all guest phases studied, where A = Li, Na, K, Rb, Cs. Exchange rates have been determined at various temperatures, and their activation energies have proved to increase more or less linearly with the enthalpy of hydration of the respective cation. The results are compared with those in solutions and possible mechanisms of proton exchange in layered intercalates are discussed.
Kinetics of the (7 × 7) ↔ (1 × 1) Transition on Si(111)
Authors: Telieps W. , Bauer E. 
Published: July 2012

AbstractThe (7 × 7) ↔ (1 × 1) phase transition was investigated in situ by low energy electron reflection microscopy (LEERM). Heterogeneous nucleation of the (7 × 7) domains at monoatomic steps is observed as well as homogeneous nucleation in the atomically flat terraces. The density of nuclei and the domain growth velocity increase with the supercooling ΔT of the surface. The domains start to grow at low ΔT in triangular equilibrium shape; interaction of neighbouring domains leads to a dendritic overall shape. The observations strongly support the view that the transition is of first order.
Order‐Disorder Phenomena in the System CO/Ru(001)
Authors: Pfnür H. , Heier H. J. 
Published: July 2012

AbstractMetal‐mediated interactions, dominant in a moderately strong chemisorbed system like CO/Ru(001), cause changes of lateral interactions not only as a function of distance between adsorbed particles but also as a function of coverage and introduce ordering mechanisms different from those observed for noble gas adsorbates. Results of a detailed LEED study are presented, carried out by photographical and by spot profile analysis. Coverage induced structural changes up to saturation coverage as well as of the order disorder transitions as a function of temperature at fixed coverage are discussed and structural models and a phase diagram are given.
A Direct Study of the Reaction CH2(X3B1) ± C2H4 in the Temperature Range 296 K ≤ T ≤ 728 K
Authors: Böhland T. , Temps F. , Wagner H. Gg. 
Published: July 2012

AbstractThe reaction between CH2‐radicals in the triplet electronic ground state X˜3B1 (3CH2) and C2H4

was studied in the gas phase at temperatures between 296 K ≤ T ≤ 728 K in an isothermal discharge flow system. CH2‐radicals were generated either in the reaction O + CH2CO or by exciplex laser photolysis of CH2CO. Their concentration was monitored with a far infrared Laser Magnetic Resonance spectrometer. The experimental rate constant obtained from the pseudo first order decay of 3CH2 in the presence of a large excess of C2H4 was found to be

Correcting for the small contribution to the depletion of 3CH2 due to collisional excitation to the singlet first excited state ã1A1(1CH2) followed by consecutive reactions of 1CH2, the rate constant for the direct reaction of 3CH2 with C2H4 was obtained to be

A reaction mechanism describing both the present data as well as the results of earlier related‐studies in the CH2 + C2H4 system is proposed. The mechanism and product yields are discussed in terms of unimolecular rate theory.
Real‐Time Neutron Powder Diffraction: A Technique for the Study of Solid State Reactions
Authors: Pannetier Jean 
Published: July 2012

AbstractThe use of large position sensitive detectors (PSD) on high flux powder diffractometers allows a powder diffraction pattern to be recorded on a time scale of a few minutes or less so that transient phenomena such as heterogeneous chemical reactions can now be studied easily. Such measurements provide direct information on the progress of a reaction (kinetic law) but may also shed light on the transformations of structure and/or morphology which occur in the reactants during the course of a reaction. The applicability of this real‐time diffraction method for investigating isothermal and temperature stimulated structural changes is illustrated by selected experiments in the field of solid state inorganic chemistry.
Ionic Transport in Heterogeneously and Homogeneously Doped Thallium (I)‐Chloride
Authors: Maier J. , Reichert B. 
Published: July 2012

AbstractThe effect of alumina admixtures on the ionic conductivity of TlCl is studied. In agreement with the model of “Heterogeneous Doping” a change of the intrinsic anionic conduction (Cl ‐vacancies) into a Tl+‐conduction (Tl+‐vacancies) is induced at lower temperatures (≦ 300 K). The experimental conductivity data as a function of temperature, concentration and grain‐size can be quantitatively described with an interface defect concentration considerably lower than for AgCl and AgBr. Likewise, for pure polycrystalline TlCl space charge regions enriched in cation vacancies around grain boundaries are assumed to provide an increase of the conductivity. Similarities and differences between heterogeneous and the classical homogeneous doping are clearly reflected by experiments using PbCl2 as a dopant for both TlCl and TlCl: Al2O3
The Electrochemical Behaviour of Manganese (II)‐Hydroxide/Magnesium Hydroxide and Manganese (II)‐Hydroxide/Calcium Hydroxide
Authors: Bauer Jügen , Buss Dieter H. , Glemser Oskar 
Published: July 2012

AbstractThe double hydroxides Mn(OH)2Mg(OH)2 and Mn(OH)2Ca(OH)2, precipitated by computer control, were investigated as positive electrodes for secondary cells in aqueous potassium hydroxide solutions with regard to charge capacity and cycling behaviour. Mn(OH)2Mg(OH)2‐hydroxides form solid solutions, whereas Mn(OH)2Ca(OH)2‐hydroxides occur as mixtures. In the system Mn(OH)2Mg(OH)2 only samples between 30 and 60 mol% Mg are electrochemically active and discharge capacities of 164–213 mAh/g are found in the first discharge process, with an oxidation state corresponding to MnO1,8. Afterwards the capacity falls to 24 mAh/g. Surprising in the system Mn(OH)2Ca(OH)2 is the rapid air oxidation of the samples with 30–50 mol% Ca to oxidation degrees of MnO1.8. These samples are further oxidized electrochemically to ∼MnO2.0, and are electrochemically active with discharging capacities between 96 and 133 mAh/g. They have a better cycling behaviour than the Mn/Mg‐species. The striking behaviour of the two double hydroxides is a consequence of their structural relationships.
High Temperature Reactions of CH3 1. The Reaction CH3 + H2 → CH4 + H
Authors: Möller W. , Mozzhukhin E. , Wagner H. Gg. 
Published: July 2012

AbstractThe rate coefficient of the reaction CH3 + H2 → CH4 + H was determined at high temperatures behind incident shock waves by time‐resolved measurements of the absorption of the methyl radical at 216.5 nm. The resulting Arrhenius expression k3 = 1013.3±0.1 exp(−(7200 ± 400) K/T) cm3 mol−1 s−1 is in good agreement with earlier indirect measurements. Several methyl radical sources are compared.
On the Decay of the Dichloride Anion Cl−2 in Aqueous Solution
Authors: Wagner I. , Karthäuser J. , Strehlow H. 
Published: July 2012

AbstractThe decay kinetics of Cl−2, produced by photolysis of chloride ions, has been studied using a flash photolysis technique with conductometric detection. Flash photolysis of Cl− ions in acid solutions eventually yields H2O2, Cl2, HClO and H2. A mechanism is proposed (Fig. 6) consistent with the experimental observations.