bluuebunny/crossref_metadata_2025 huggingface dataset:
Untersuchungen über die Wechselwirkung von ungesättigten Verbindungen mit Lewissäuren IX. IR‐spektroskopische Untersuchungen über die Wechselwirkung von Alkenen und Cycloalkenen mit Aluminiumbromid im festen Zustand
Authors: Perkampus H.‐H. , Weiß W.
Published: March 2014

Im binären System Alken/Al2Br6 bzw. Cycloalken/Al2Br6 wird eine Verschiebung der C = C‐Valenzschwingung in der Größenordnung von 50 ‐ 70 cm−1 zu niederen Wellenzahlen beobachtet. Dieser Effekt wird der Bildung eines π‐Komplexes zugeschrieben. Die Größe dieser Verschiebung steht im Widerspruch zu dem von Terenin angegebenen Wert von – 125 cm−1. Es läßt sich aber zeigen, daß im ternären System Alken/Al2Br6/HCl bzw. Cycloalken/Al2Br6/HX eine Verschiebung dieser Größenordnung beobachtet wird. Es kann somit gezeigt werden, daß es sich bei der von Terenin angegebenen Verschiebung von ‐ 125 cm−1 um die Bildung eines Proton‐Komplexes handelt.
Ultrasound Propagation and the Volume Expansion Minimum in Potassium‐Ammonia solutions
Authors: Parker M. H. , Bowen D. E.
Published: March 2014

The volume expansion minimum reported by Evers and co‐workers was not seen when the measurements were repeated by Gunn and Green. In an attempt to detect this minimum, careful measurements of the velocity of ultrasound waves in potassium‐ammonia solutions have been performed. These measurements were made as a function of both temperature and metal concentration in the region of the reported minimum using a pulse superposition technique accurate to within one part in 104. The velocity is a linear function of the temperature and can be expressed by the equation:.

A minimum in C1 at the same concentration as the volume expansion minimum was seen; however, the relative errors present in C1 are such as to make confirmation of the volume expansion minimum doubtful.
Pressure and Temperature Dependence of Optical Properties of Potassium‐Ammonia and of Potassium Iodide‐Ammonia solutions
Authors: Vogelsgesang R. , Schindewolf U.
Published: March 2014

The absorption spectra of dilute potassium‐ammonia solutions, in which solvated electrons are present, and of potassium iodide‐ammonia solutions (ctts‐spectrum) are in a restricted temperature range shifted with increasing temperature to longer wave‐lengths and with increasing pressure to shorter wave‐lengths. These shifts are interpreted in terms of thermal expansion and of compression resp. of the solvation shells around the electrons and the iodide ions resp. (cavities) the size of which determines the wave‐length of light absorption. At higher temperature however the effects reverse their signs, indicating that the relationship between cavity size and position of the absorption maximum is not unambiguous.

The reflectivity of concentrated potassium ammonia solutions increases with temperature but decreases with pressure. The reflectivity behaviour of the solutions therefore parallels their behaviour of electrical conductivity.
Organic Dye Laser Properties and Orientational Relaxation Processes
Authors: Gronau B. , Lippert E. , Rapp W.
Published: March 2014

The system 2‐amino‐7‐nitrofluorene/1,2‐dichlorobenzene was found to show laser action. Contrary to hitherto known dye lasers this system exhibits a blue shift of the dye laser spectrum with increasing dye laser intensity, dye concentration and resonator Q. During emission of a single pulse, the dye laser spectrum shows a blue shift with proceeding time. These effects are explained by orientational relaxation processes of the polar solvent molecules.
Messungen der scheinbaren Molwärme von Wasser in Zeolithen vom Faujasit‐Typ
Authors: Basler W. D. , Lechert H.
Published: March 2014

Die scheinbare Molwärme von Wasser, welches in Poren verschiedener Zeolithe vom Faujasit‐Typ adsorbiert war, wurde im Bereich 90‐300 K für verschiedene Belegungen gemessen. Die Ergebnisse zeigen, daβ das adsorbierte Wasser sich bei 300 K wie eine Flüssigkeit verhält. Beim Abkühlen wird keine Kristallisationswärme beobachtet, sondern das Wasser erstarrt bei 200 ‐ 220 K zu einem amorphen Festkörper. Die Übergangstemperatur flüssig‐fest kann mit der Annahme berechnet werden, daβ sie der Sorptionsenergie proportional ist. Der Einfluß der Kationen auf das Verhalten der intrakristallinen Flüssigkeit ist nur gering.
Nachweis und thermisches Verhalten von CdOgas über festem CdO
Authors: Grade M. , Hirschwald W. , Stolze F.
Published: March 2014

Die Existenz einer gasförmigen CdO‐Molekel wurde massenspektrometrisch mit Hilfe eines empfindlichen, hochauflösenden Massenspektrometers mit integrierter Knudsenzelle nachgewiesen und ihre Konzentration im Gleichgewicht mit festem Cadmiumoxid als Funktion der Temperatur gemessen. — Zwei gekoppelte Bildungsgleichgewichte werden zur näherungsweisen Berechnung der Dissoziationsenergie D0CdO der CdOgas‐Molekel aus der gemessenen Temperaturabhängigkeit in Betracht gezogen, in Analogie zu früheren Berechnungen für gasförmiges Zinkoxid [1]. Als Mittelwert für D0 ergibt sich:
Stress Induced Drift Diffusion in Grain Boundaries – Application to Creep and to the Growth of Grain Boundary Voids
Authors: Trinkaus Helmut
Published: March 2014

The diffusional matter transport in grain boundaries under the influence of stress fields is discussed. The most important relations, connected with the scaling behaviour of the basic equations, can be deduced from simple estimates. On this basis it is shown (1) that the range of a matter inhomogeneity in a grain boundary and that of the related stress field develop in time as t1/3, (2) that in the early stage the diffusional creep deformation goes with t2/3, (3) that under constant stress isolated grain‐boundary voids grow with constant volume growth rate. The time to brittle fracture caused by simultaneous nucleation and growth of grain‐boundary voids is discussed.
Physico‐Chemical Interaction between Biominerals and their Environment
Authors: Driessens F. C. M.
Published: March 2014

A reconsideration of literature data reveals that the incorporation of vacancies, Na, K, Sr, Cl, and CO3 into hydroxyapatite increases its apparent solubility product, whereas that of F decreases it. It is further shown that the composition of saliva is regulated so that a steady state is reached for erupted teeth whereby equilibrium between mineral and saliva is close to the two‐phase boundary of apatite and dicalciumphosphatedihydrate (DCPD). The theory explains qualitatively why and how gradients occur of F, Na, and CO3 in surface enamel, why the surface layer remains nearly intact during caries and why calcifications occur in the arteries and not in the veins. – It is assumed that the incorporation of Mg and citrate ions can increase the apparent solubility product of tricalciumphosphate (TCP) and octacalciumphosphate (OCP) respectively. On this basis an estimate is made of the relative position of the stability fields of apatite, DCPD, TCP, and OCP. This estimate indicates why these calcium phosphates may occur simultaneously in dental calculus, bone, dentine and pathological calcifications. If both the effect of crystal size and that of incorporation of foreign ions are taken into consideration, it can be presumed that calcified tissues are in momentary physico‐chemical equilibrium with the body fluids bathing them.
The Influence of H – H Pairing on the Diffusional Behaviour of Hydrogen in Niobium
Authors: Boes N. , Wicke E.
Published: March 2014

The energy of interaction of neighbouring H atoms is estimated by a simple model for the elastic strain on the metal lattice by interstitial hydrogen. This energy is compared with results obtained by the measurement of thermodynamic equilibrium data in the system Nb/H. – A jump model considering this interaction is proposed for the diffusion of paired H atoms. It explains the observed anomalous temperature dependence of the diffusion coefficient of hydrogen in niobium. – On the basis of this novel process of diffusion the elimination of the anomaly by additionally solved impurities like oxygen or nitrogen can be understood.
Two Routes in the Formation of Hydrogen Halides from OH Adducts of Halogenated Anisoles in Aqueous Solution
Authors: Latif N. , O'Neill P. , Schulte‐Frohlinde D. , Steenken S.
Published: March 2014

Using pulse radiolysis with conductivity detection and steady state γ‐radiolysis it is shown that in aqueous solution the reaction of OH radicals with 2,3‐ and 4‐monohalo (X = F, Cl, Br) anisoles leads to the production of hydrogen halides (HX). The G‐values for production of hydrogen halides measured 10 μs after the pulse are large for the 2‐ and 4‐haloanisoles (G(HX) = 0.5‐1.45) and small for the 3‐haloanisoles (G(HX) = 0.1‐0.3). These yields reflect the amount of OH addition to ring positions substituted by X. The differences in these amounts reflect an ortho‐para directing activity of the methoxy group. – In the case of the OH adducts of 3‐haloanisoles – in contrast to those of 2‐ and 4‐haloanisoles – in addition to the prompt a second order elimination of HX is observed which occurs on the ms time‐scale. This shows that the distribution of OH addition cannot always be obtained from product studies using γ‐radiolysis. The G(HX) values measured using steady state γ‐radiolysis agree with those determined in the ms range using pulse radiolysis.
Two‐ and Three‐Dimensional Reactions of Ag+2 Radical Cations in Aqueous Solutions of Anionic Tensides
Authors: Henglein A. , Proske Th.
Published: March 2014

Ag+2 radical cations were produced in aqueous 1 · 10−4 molar Ag2SO4 solutions containing micelles of sodium hexadecyl trioxiethylene sulfate and of sodium dodecylsulfate by a short pulse of high energy electrons. The disappearance of Ag+2 and the appearance of Ag2 were followed by optical measurements in the 10−6 to 10−2 s range. – A fraction of the Ag+2 radicals decayed within 1 to 2 microseconds, and the remaining radicals disappeared in a second order process within 10−4 to 10−2 s. These decay processes are attributed to

(a) intramicellar or two‐dimensional radical‐radical reaction at the surface of doubly occupied micelles, and

(b) intramicellar or three‐dimensional reaction between radicals that are singly adsorbed at micelles. The fraction of (a) increases with increasing concentration ratio of radicals to micelles as expected from statistical considerations. Deviations at low concentration ratios are attributed to the initial formation of some of the radicals in spurs. The observed 100 fold acceleration of the radical‐radical reaction by the reduction in the dimensionality of reaction space is also compared to similar effects in fast biochemical reactions on large carrier molecules.

It is concluded from an analysis of the dependence of the bimolecular rate constant of reaction (b) on the tenside concentration that Ag+2 cations reside longer than milliseconds at micelles and can be exchanged directly between two anionic micelles. The rate constants are given for the two tensides.
Substitution Reactions of Beryllium (II) Ion in Mixed Solvents. I. The Beryllium Sulphate Complex in Water‐Formamide Mixtures
Authors: Lachmann R. , Wagner I. , Devia D. H. , Strehlow H.
Published: March 2014

The formation of the inner‐sphere complex of BeSO4 in mixtures of water and formamide has been investigated using the pressure‐jump relaxation method. Whereas in the two pure solvents the reaction is characterized by a single relaxation time in the solvent mixtures two relaxation processes superimpose and which are attributed to the replacement of a water or a formamide molecule, respectively, in the inner‐sphere by the entering sulphate ion. – The multistep association mechanism proposed by Eigen and Tamm [1] prevails also in the solvent mixtures. With increasing mole fraction of formamide the dielectric constant increases and in accordance with Fuoss equation [2] the association constants of the outer‐sphere complexes decrease. However, the inner‐sphere stability constants increase sharply so that the total association constants of BeSO4. increase with the formamide content. The ligand assisted dissociative process (Id [3]) outer‐sphere r̊ inner‐sphere complex is discussed in terms of a concerted mechanism proposed earlier for aqueous solutions [4].
Diffusion Limited Oxygen Quenching of Photo‐Induced Electrochemical Reactions in Sandwich Systems with Molecular Crystals
Authors: Killesreiter Hermann
Published: March 2014

Photoelectrochemical reactions in sandwich systems with the dye 3,3′‐distearyl‐oxacarbocyanine chlorate adsorbed in monolayer assemblies on p‐chloranil single crystals have been used to demonstrate the quenching action of paramagnetic oxygen on sensitized as well as on triplet exciton induced photocurrents. Simultaneously, the presented measurements are a method to study the lateral diffusion of oxygen into monolayer assemblies between the crystal surface and an evaporated aluminum electrode by photoelectrical detection. From the functional time dependence of a reciprocal square‐root law and together with the discussion of a kinetic scheme the rate constants for the quenching of excited dye molecules and of n‐π*‐triplet excitons at the phase boundary could be evaluated to be kq = 2.5 · 1012 M−1 s−1 and 3kq = 1012 M−1 s−1, respectively, on the basis of an estimated upper limit for the diffusion coefficient D = 4 · 10−6 cm2 s−1 for oxygen diffusion into the slab with a bilayer structure. – The method has been extended to sandwich systems with rhodamine B on the surface of anthracene and p‐chloranil crystals that showed no effect due to oxygen, whereas the systems cyanine dye/anthracene revealed less marked photocurrent enhancements as well as decreasings. These results are discussed in terms of hindered oxygen access and of an extended reaction scheme that involves the well‐known oxidizing action of oxygen in sensitization.
1H and 19F Nuclear Spin‐Lattice Relaxation in Solid [X(CH3)4]2SiF6, X = N, P, As and Sb
Authors: Rager H. , Weiss Alarich
Published: March 2014

The spin‐lattice relaxation times T1(1H) and T1(19F) in the solid compounds [X(CH3)4]2SiF6, X = N, P, As, and Sb, were studied in the temperature range 125 K ⩽ T ⩽ 460 K at a NMR frequency of 34 MHz. In the low temperature region protons and fluorine nuclei are coupled by dipole‐dipole interactions and both spin systems relax mainly through the motions of the methyl groups. The activation energy of the methyl group reorientation, Va, decreases with increasing size of the cation. With increasing temperature both T1(1H) and T1(19F) are influenced by the reorientation of the cations as a whole. The activation energy Va1 of the reorientation of [X(CH3)4]+ was determined. From the linewidths of the free induction decays it is concluded that the dynamical behavior of the compounds is mainly determined by the size of the cations. The influence of the anion on T1, is small causing a slight increase of the activation energy Va compared to Va in [X(CH3)4]I. From the Raman spectrum of [N(CH3)4]2SiF6 a 90° reorientation mechanism of the cation seems most probable.
The Influence of Amphiphilic Substances on the Mutual Solubilities in Binary Liquid Systems (Microemulsions)
Authors: Herrmann C.‐U. , Würz U. , Kahlweit M.
Published: March 2014

This paper summarizes the first results of an investigation on the influence of amphiphilic substances on the mutual solubilities of two partially miscible liquids. In the first part, the ternary system C6H6–H2O – Alcohol are studied and in the second part, the quarternary systems C6H6 – H2O – Alcohol – NaDS. The effectivity of different alcohols is discussed as well as the influence of the surfactant on the shape of the phase diagram. The microscopic structure of the solutions was investigated by means of light scattering, small angle X‐ray scattering, and conductivity measurements. The structure of the micelles in different regions of the phase diagram is discussed. The results indicate the existence of a critical composition for the formation of inverse micelles in the C6H6 rich region.
A Proton Magnetic Resonance Investigation of Molecular Motion and Phase Transition in Solid Diamminesilver Dinitroargentate, [Ag(NH3)2]Ag(NO2)2
Authors: Maurer H. M. , Ragle J. L. , Weiss Alarich
Published: March 2014

The second moment and the spin‐lattice relaxation time, T1, of the proton magnetic resonance have been studied in a polycrystalline sample of diamminesilver dinitroargentate. The broadline measurements indicate that the ammine groups reorientate rapidly around their triad axes. A phase transition has been detected by differential thermal analysis at −91°C. Activation energies for the reorientation of 7.20 ± 0.38 kJ mol−1 and 9.96 ± 0.30 kJ mol−1 are derived from the T1‐measurements for the room temperature phase (I) and the low temperature phase (II), respectively. The results are discussed on the basis of the crystal structure. The phase transition can be described by a change from an ordered to an orientationally disordered arrangement of the nitrite ions.
Spectroscopy of Minerals
Authors: Lehmann Gerhard
Published: March 2014

Examples for the application of five spectroscopic methods to mineralogical problems which exceed a mere characterization are discussed. In addition in some examples results of infrared and optical absorption as classical spectroscopic tools are also used. In many cases the nonideal compositions and structures of the minerals are of decisive influence upon the results, and sometimes they even generate the observed phenomena.
Picosecond Polarization Spectroscopy of Dye Molecules
Authors: Reiser D. , Laubereau A.
Published: March 2014

Theoretical and experimental data are presented on the propagation of picosecond pulses in weakly excited dye solutions. We report a new version of the pump and probe technique, measuring induced dichroism at variable probe pulse frequency. It is shown that the so‐called “coherence peak” in experiments with equal pump and probe frequencies depends on the vibronic relaxation and excited state absorption of the dye molecules. Measurements with different pump and probe frequencies allow to distinguish rotational relaxation times in different electronic states. Interpretation of the experimental data is considerably facilitated at the low excitation intensities used here. Experimental results for vibronic and rotational time constants on phenoxazone 9 and rhodamine 6G are presented.
From Micellar Solutions to Liquid Crystalline Phases
Authors: Hoffmann H.
Published: March 2014

The types of micelles and their sizes which exist in surfactant solutions in the isotropic concentration range in between the critical micelle concentration (Ccmc) and the concentration for liquid crystal formation (Cl.c.) are discussed. Four different types of ionic surfactants are treated:

single chain surfactants with a cubic phase as the first l.c. phase

single chain surfactants with a hexagonal phase as the first l.c. phase

double chain surfactants with a lamellar phase as the first l.c. phase

perfluoro‐surfactants.
Vergleich der Perturbed‐Hard‐Chain‐Theorie mit der Freien‐Volumen‐Theorie und der Flory‐Huggins‐Theorie zur Berechnung von Phasengleichgewichten von Ethylen/Polyethylen‐Mischungen unter Hochdruck
Authors: Jungermann Georg , Luft Gerhard
Published: March 2014

The perturbed‐hard‐chain theory, the free‐volume‐theory and the well known Flory‐Huggins lattice theory of polymer solutions were applied to phase‐equilibrium calculations for mixtures of ethylene and low density polyethylene. The parameters required for the calculations were determined from a large number of experiments under high pressure. By comparison of calculated and measured phase‐equilibrium data it is shown that the perturbed‐hard‐chain‐theory can be applied to predict accurately composition of phases as well as the molar mass of the polymer in the ethylene‐ and in the polyethylene‐rich phases from ambient to high pressure. The free‐volume‐theory failed for pressures near the critical. The solubility of ethylene in the polymer‐rich dense phase could be calculated by means of Flory‐Huggins‐Theory only for low to medium pressures up to 300 bar in good agreement with the experimental data. By means of the perturbed‐hard‐chain‐theory engineers may interpolate and extrapolated limited experimental data with confidence for optimal design of large scale polymerization reactors and separators.
Slit length correction of slowly decaying small‐angle X‐ray scattering‐patterns using a formal extrapolation of the pinhole curve searched for
Authors: Ledent J. , Fontaine F. , Reynaers H.
Published: March 2014

Starting from the desmearing method used in small‐angle X‐ray scattering (SAXS) investigations which is based on the processing of a set of linear equations, a procedure is proposed to compute in a single step the pinhole curve as well as an extrapolation curve of the latter towards the wide angles. To this end a small number of parameters are added to the unknowns of the problem to fix some known boundary conditions towards the wide angles. Before solving the equations the added parameters are expressed in terms of the intensity‐unknowns in order not to increase their number. The procedure is presented in the frame of the analysis of SAXS‐data recorded from samples the structure of which can be described by the two‐phase concept.
The influence of water and of alkali promotor on the carbon number distribution of fischer‐tropsch products formed over iron catalysts
Authors: König L. , Gaube J. , Meisel W. , Gütlich P. , Gerhard W. , Plog C.
Published: March 2014

The carbon number distribution of Fischer‐Tropsch products formed over an alkalized precipitated iron catalyst has been studied as a function of the water vapor pressure of the synthesis gas. The carbon number distribution of formed hydrocarbons is characterized by a bimodal Schulz‐Flory distribution of growth probabilities P1 ≈ 0.6 and P2 ≈ 0.87 attributed to unpromoted and promoted (alkalized) sites on the catalyst surface. Promoted sites are more stable with respect to oxidation (deactivation) by water than unpromoted sites. The growth probability of unpromoted sites decreases with increasing ratio P/P — Studies using Mössbauer spectroscopy have shown that iron foils treated with water containing some K2CO3 yield smaller fractions of iron oxides at the surface than those treated with pure water. Also studies on reduced precipitated iron catalysts using SIMS have shown that alkaline treatment reduces the oxidation of iron by water. These results are interpreted in terms of electronic effects.
Analysis of “two‐electron” transfer processes by cyclic voltammetry
Authors: Hinkelmann Klaus , Heinze Jürgen
Published: March 2014

The cyclic voltammetric response for “two‐electron” transfer processes is studied for magnified image. Evaluation of the EE mechanism has been generalized to those cases where the standard heterogeneous rate constants k01 and k02 of both charge transfer steps may take any value between the reversible and irreversible limits and differ by one to two orders of magnitude. A correct interpretation of the cyclic voltammograms demands that the homogeneous disproportionation reaction: 2B ⇋ A + C be included (EE‐DISP). Simulated voltammograms and working curves are presented. Their use opens a way for the quantitative determination of the thermodynamic and heterogeneous kinetic parameters of “two‐electron” transfer reactions.
The jellium model in electrochemistry
Authors: Badiali J. P.
Published: March 2014

We examine the direct contribution of the metal to the differential capacitance of an ideally polarizable electrode. We discuss the extension of the jellium model to the case of noble metals. A simple and rather realistic model is proposed for describing the electronic structure of these metals. We check this model by investigating the electronic work function and its variation with the cristallographic orientation of the surface. Satisfactory results are obtained. As a first step in the calculation of the capacitance we study the response of the metal to an external charge. We may conclude that the metal has certainly a large contribution to the capacitance. Moreover, the correct variation of the capacitance with the orientation of the surface is predicted although the absolute determination of the capacitance seems to be extremely difficult.
Infrared spectroscopy of the electrochemical double layer via electrode emersion
Authors: Hansen Galen J. , Hansen Wilford N.
Published: March 2014

Infrared reflection Spectroscopy was used via electrode emersion to study both adsorbed and non‐specifically adsorbing species within the electrochemical interphase on gold, ex situ. A cell was designed which allowed the electrode to rotate and continuously emerse from solution. The parallel‐polarized IR beam was reflected from the rotating surface above the solution at approximately 80°. FTIR spectra were taken of gold electrodes emersing from aqueous solutions of crystal violet, HCIO4, and D2SO4 at various electrode potentials, and ratioed as a function of potential. Active vibrational bands of crystal violet which strongly adsorbs to the gold, and of ClO4− and SO42− ions within the more ideally‐polarizable double layer, are easily seen. Changes in band intensities as a function of potential are, to first order, as expected.
Electroreflectance at the semiconductor/electrolyte interface. A comparison of theory and experiment for n‐GaAs
Authors: Abrantes L. M. , Peat R. , Peter L. M. , Hamnett A.
Published: March 2014

The electroreflectance spectra of GaAs in a number of different electrolytes have been measured in the neighbourhood of the E0 transition. The spectra have been found to exhibit appreciable differences suggestive of changes in the potential distribution in the depletion layer. In one case, that of n‐GaAs in 0.1 M KOH, a detailed analysis has been carried out of lie electroreflectance spectrum using an intermediate field model and incorporating a linear field distribution within the depletion layer. A good fit to the experimental data is obtained from this model and it is found that about 70% of the potential change at the interface is accomodated across the depletion layer.
Electrochemical photooxidation of carboxylates on CdS electrodes
Authors: Feiner A. S. , McEvoy A. J. , Vlachopoulos N. , Grätzel M.
Published: March 2014

Photoelectrochemical oxidation of formate and of some α hydroxycarboxylate species took place at CdS semiconductor photoanodes. The mechanism of the formate dissociation, yielding carbon dioxide and hydrogen, was investigated. The hydroxy groups of the hydroxycarboxylate ions were oxidised to the corresponding ketones. Current enhancement (“current doubling”) effects were noted. The photooxidative reactions competed effectively with CdS photocorrosion.
Stabilization of CdS and CdSe photoelectrodes modified by a catalyst‐containing polythiophene coating
Authors: Gningue Diariatou , Horowitz Gilles , Gamier Francis
Published: March 2014

The protection of CdS and CdSe by a conductive polymer is studied in aqueous solutions of ferrous/ferric redox couple and lithium perchlorate indifferent electrolyte. The polymer is poly(bithiophene) which is grown photoelectrochemically in an acetonitrile solution containing the dimer 2,2′‐bithiophene and lithium perchlorate as the supporting salt. The dimer was chosen as the starting material because photocorrosion of the semiconducting substrate competes with electropolymerization when using a solution of the monomer, leading to very unhomogeneous and poorly adhesive polymers. The protection by the as grown polymer against photodegradation of the semiconductor in an aqueous solution is rather poor, due to a spontaneous reduction of the polymer to its neutral form where its conductivity is lowered by several orders of magnitude. A significant improvement of the protection is obtained by including noble metal clusters on the polymer overlayer. The inclusion is realized by electrochemical reduction of a salt of the metal.
Migration of high energy defects after Pd‐implantation in oxide films on titanium
Authors: Elfenthal L. , Leitner K. , Schnltze J. W. , Meyer O.
Published: March 2014

Ion implantation in oxide films causes a structural amorphization and high energy lattice defects which influence the electrode capacity, electron transfer reactions and photo processes. Repassivation taking place continuously with increasing potentials yields a migration and annihilation of defects which can be followed by the same measurements, each of them reflecting different aspects. The repassivation charge refers to the defect migration and new oxide formation. The capacity shows the decrease of the dielectric constant D and the donor concentration N. Electron transfer measurements prove the migration of ions with electronic states near the Fermi level EF and the growth of insulating layers. The photocurrent demonstrates the decrease of amorphicity with repassivation.
High Temperature Reactions of CH3 2. H‐Abstraction from Alkanes
Authors: Möller W. , Mozzhukhin E. , Gg. Wagner H.
Published: March 2014

The rate coefficients of the reactions CH3 + C2H6 → CH4 + C2H5 (1) and CH3 + CD4 → CD4 → CH3D + CD3 (2) were 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 expressions

k1 = 1013.3±04 exp (−(6800 ± 1000) K/T) cm3 mol−1 s−1 1100 < T/K < 1400

k2 = 1013.8+06 exp (−(8800 ± 1600) K/K) cm3 mol−1 s−1 1100 < T/K < 1500

are in good agreement with earlier indirect measurements at high temperatures. Comparison with data at lower temperatures leads to strongly curved Arrhenius plots.
Molecular Orientation and Photoelectric Properties of Alloxazine Monolayer Assemblies
Authors: Nagamura Toshihiko , Matano Koichi , Ogawa Teiichiro
Published: March 2014

Langmuir‐Blodgett (LB) films of an alloxazine derivative with two dodecyl chains at 1,3‐positions showed UV/vis dichroism at normal incidence. Spectral shifts indicating aggregation of chromophores were also observed. Angular dependences of polarized absorption spectra indicated that alloxazine rings were biaxially oriented with respect to the film plane and to the dipping direction. The molecular orientation of alloxazine rings in the film plane was suggested to be induced during the transferring process of monolayers. Alloxazine LB films showed photoelectric responses corresponding to the absorption spectra. The in‐plane photoconductivity was almost isotropic and was greater than that of the through‐plane one by about five orders of magnitude.
Homogeneous Optical Linewidth of Impurities in Organic Glasses in the Low Temperature Regime
Authors: Reineker P. , Kassner K.
Published: March 2014

We present a microscopic model for the dephasing of optical impurities in amorphous hosts. To describe the dynamics of the glass an ensemble of two‐level systems (TLSs) is introduced, a well‐known procedure. The TLSs are coupled to an impurity as well as to the matrix vibrations, which we consider a heat bath. A lineshape expression from linear response theory is evaluated for the cases of both a single TLS and many TLSs interacting with the impurity. We find that the magnitude of experimental linewidths can be explained only, if the latter situation is realized. We offer several explanations of the temperature dependence of experimentally observed dephasing rates which are all compatible with the mathematical structure of the theory.
Microwave Conductivity in the Pure and Iodine‐Doped Organic Conductor α‐(BEDT‐TTF)2I3
Authors: Kremer W. , Helberg H. W. , Gogu E. , Schweitzer D. , Keller H. J.
Published: March 2014

The microwave conductivity in dependence of temperature was measured on pure and iodine doped crystals of α‐(BEDT‐TTF)2I3 along the stack direction [100] and perpendicular to it [010]. The exposure times to iodine were varied in many steps between 2 min and 360 min. The contactless microwave technique enables to keep the same crystal in each case throughout all measurements. — The results show that the microwave conductivity vs. temperature is not influenced distinctly by iodine doping. Only at the onset of the plateau range immediately below the metal‐insolator transition at 135 K a small enhancement of the conductivity is found for exposure times larger than 60 min. — In no case a transition to a superconducting state is observed. Therefore recently reported superconductivity may be due to surface effects.
Polymeric Phthalocyanines and their Precursors, 13 Synthesis, Structure and Electrochemical Properties of Thin Films of Polymeric Phthalocyanines from Tetracarbonitriles
Authors: Wöhrle Dieter , Schmidt Volker , Schumann Bernd , Yamada Akira , Shigehara Kiyotaka
Published: March 2014

Thin films (45 – 1200 nm thickness) of polymeric phthalocyanines were prepared by the reaction of copper films on various carriers with gaseous aromatic tetracarbonitriles. The films were characterized by IR, UV/VIS, and ESCA spectra. The electrical conductivity is in the order of 10−2‐10−5 S cm−1. The electrochemical activity of the films on graphite was studied in acid and alkaline electrolyte. The films exhibit rapid reduction and reoxidation. The pH dependence corresponds to that of the hydrogen electrode approximately.
Bidirectional Coupled Diffusion of Glycine Driven by pH Gradients
Authors: Leaist Derek G.
Published: March 2014

Stokes magnetically‐stirred diaphragm cells have been used to determine multicomponent diffusion coefficients for aqueous glycine + hydrochloric acid + sodium hydroxide solutions at 25°C. In acidic solutions, pH gradients drive coupled flows of glycine toward the low‐pH region of the solution, countercurrent to the flow of H+ ions. In alkaline solutions, the coupled flow of glycine travels in the opposite direction, “up” the pH gradient. The diffusion measurements also show that gradients in concentration of glycine can produce large coupled flows of H+ and OH− ions. Equations are developed to predict multicomponent transport coefficients for glycine and related ampholytes in acid‐base solutions.
Determination of the Effective Charge Numbers of Colloidal Spheres by Electrophoretic Mobility Measurements
Authors: Okubo T.
Published: March 2014

The effective charge number of colloidal spheres was determined for monodisperse polystyrene latices (91∼2950 nm in diameter and 1.0 ∼ 3010°C/cm2 in charge density) by electrophoretic mobility measurements. The fraction of free macroions and/or gegenions (β) in deionized suspension is smaller than unity and decreases rapidly with increasing sphere analytical valency (Z). The relation, logβ = 2.61‐0.87 log Z is obtained for the deionized suspension. The β‐value decreases on the addition of sodium chloride. β for the organic solvent‐water mixtures (organic solvents: methanol, ethanol, propanol, 1,4‐dioxane, ethylene glycol, propylene glycol, N‐methylformamide. and N‐methylacetamide) is determined as a function of volume fraction of the organic solvent.
Electronic Spectra and Structures of Cation Radicals Produced from p‐Phenylenediamine and 2, 7‐Diaminonaphthalene
Authors: Hoshi Toshihiko , Okubo Jun , Yananoto Masanori , Tanabe Seiichi
Published: March 2014

Polarized absorption spectra of cation radicals produced from p‐phenylenediamine and 2,7‐diaminonaphthalene have been determined in poly(vinyl alcohol) matrices (PVA film) at 97 K. Partially oriented free radicals in the PVA films to measure the polarized absorption spectra were prepared by two methods: (1) irradiation of p‐phenylenediamine with a polarized UV light in the unstretched (isotropic) PVA film at 97 K, and (2) irradiation of 2,7‐diaminonaphthalene with an unpolarized light in the stretched (anisotropic) PVA film at 97 K. – The 498 nm and ∼330 nm bands of the cation radical of p‐phenylenediamine are polarized along the longer molecular axis (Z), and these bands correspond to the calculated transitions (2B3u→2B2g), D1 → Do and D3 → D0, respectively. The 375 nm band is polarized along the shorter molecular axis, and assigned to D2 → D0 (2Au → 2B2g). The odd electron of this radical is almost localized on the two nitrogen atoms. – The 580 nm band of the cation radical of 2,7‐diaminonaphthalene is polarized along the shorter molecular axis (Z, C2 axis), and assigned to the calculated transition D1 → Do (2A2 → 2A2). The 477 nm and ∼400 nm bands correspond to the calculated transitions (2B → 2A2) D2 → Do and D3 → Do, respectively, and these transitions are polarized along the longer molecular axis. In this case, the odd electron is localized on the two nitrogen atoms by 84% and on the two carbon atoms at 1 and 8 positions by 15%.
Molecular motions from two‐dimensional NMR of powders: Comparison of rotational jumps and diffusive reorientations
Authors: Schmidt C. , Blümich B. , Wefing S. , Kaufmann S. , Spiess H. W.
Published: March 2014

With the two‐dimensional (2D) exchange NMR experiment on polycrystalline or amorphous solids it is possible to study reorientations in the slow motion limit. Anisotropic interactions lead to 2D powder spectra exhibiting characteristic singularities (“ridges”). From such a powder spectrum the relative orientations of a coupling tensor at the beginning and at the end of the mixing time can be measured without reference to any model of reorientation. The method is demonstrated for hexamethylbenzene and linear polystyrene.
Schwingungsenergieumverteilung in Lösung
Authors: Kaiser W. , Seilmeier A.
Published: March 2014

Large molecules are vibrationally excited via resonant absorption of infrared picosecond pulses or via electronic absorption and subsequent rapid internal conversion. The relaxation of vibrational energy is monitored by a second light pulse which measures changes in the long‐wavelength tail of the electronic absorption. Very rapid intramolecular energy redistribution (τinter < 2 ps) is observed, followed by intermolecular energy transfer to the surrounding (tinter ∼ 10 ps).
The orientation axis comparison of order parameters of anthraquinone dyes in a liquid crystal phase
Authors: Kuball H.‐G. , Strauss A. , Kappus M. , Fechter‐Rink E. , Schönhofer A. , Scherowsky G.
Published: March 2014

Three different molecule‐fixed coordinate systems have a distinct significance for the calculation of order parameters. Only one of them is suitable to define an orientation axis (x*3) in order to obtain order parameters which can be used for a comparison between systems of different molecules. For the majority of point symmetry groups, these axes x* are fixed by symmetry. The selection of the orientation axis x*3 from the x3 depends on a special quantitative condition. By means of 15 aminoanthraquinones dissolved in the compensated nematic phase of cholesteryl chloride/cholesteryl laurate and in addition some of them in ZLI 1695 (Merck), the consequences of the choice of the reference axis x3 for determining order parameters have been analyzed. By this it has been shown experimentally that order parameters ‐ measured by different methods IR, UV, e. g. ‐ are only comparable if they refer to x*3. For two dyes (4,12) the orientation axis x*3 switches about π/2 depending on the special type of substituents. For the structure ‐ order parameter relation it has been shown that the 15 dyes can be arranged in two series. One series obeys the usual rule of increasing S* with increasing length to width ratio. The second series does not fit in this dependence.
X‐ray absorption spectroscopy of amorphous rare‐earth transition‐metal oxides
Authors: Torkler A. , Beuthien H. , Gunßer W. , Niemann W.
Published: March 2014

Amorphous rare‐earth transition‐metal oxides (a‐YFeO3, a‐GdCrO3) were prepared by annealing the co‐precipitated hydroxides. The short‐range order shows a strong dependence on the annealing process. Structural parameters were determined by EXAFS investigations at the K edges of the transition metals. In a‐YFeO3 the iron oxygen distances and the coordination numbers are both considerably lower than in the crystalline structure. Cr K‐EXAFS and XANES measurements on a‐GdCrO3 indicate the existence of a mixture of octahedrally and tetrahedrally coordinated chromium. Furthermore, a shift of the Cr‐K‐absorption edge during the annealing process is evidence of a changing chromium valence.
The static structure factor of cesium over the whole liquid range up to the critical point
Authors: Winter R. , Hensel F. , Bodensteiner T. , Gläser W.
Published: March 2014

The paper presents the first neutron scattering investigation of the static structure factor S(Q) of expanded liquid cesium from the melting point up to its critical point at conditions near the liquid‐vapour coexistence curve (critical data of cesium: Tc = 1924 K, pc = 92.5 bar, dc = 0. 379 g/cm3). The characteristic changes of the microscopic structure — such as the distance and number of nearest neighbours — are derived as a function of density. The reported results give useful information about the density dependent changes in the electronic structure in course of the transition from a metallic to a nonmetallic state which occurs in the expanded metal. In particular, the results provide direct experimental evidence for the limitation of the nearly‐free‐electron (NFE) model in describing the electrical transport properties of low density fluid cesium.
Generation and deactivation of 1O2 (1Δ) by helianthrene and helianthrene‐derivatives
Authors: Acs A. , Schmidt R. , Brauer H.‐D.
Published: March 2014

The photooxygenation of helianthrene (H), mesodiphenylhelianthrene (MDH) and mcsodiphenylbenzhelianthrene (MDBH) has been studied kinetically by several independent methods in different solvents. The results indicate that singlet oxygen (1Δ) is generated only by oxygen quenching of the lowest triplet states via the process: T1 + 3Σ ↔ So + 1Δ, which occurs with unit efficiency for all three hydrocarbons. H is the most reactive 1Δ‐acceptor hitherto known. In solvents of low viscosity like acetone the rate constant of reaction is kτ = 4.6 · 109 M−1 s−1. MDH and MDBH are not only very reactive 1Δ‐acceptors but also efficient 1Δ‐quenchers. In a mixture of toluene and methanol (1 Vol.%) for MDBH the rate constants of physical quenching and photooxygenation amount to k11n = 6.3 · 109 M−1 s−1 and k7 = 0.2·109 M−1 s−1.
Acid‐Base‐Equilibria at Semipermeable Membranes, their Influence on pH‐Triggered Permeabilities
Authors: Schlögl Reinhard W. , Hirsch‐Ayalon Paul
Published: March 2014

The theory of Donnan‐equilibria is extended to systems in which chemical equilibria are involved. Equal temperatures of the outer phases, as well as ideal solutions are assumed. The membranes shall be impermeable for at least one ionic species. Comparison of the theory with experimental data at precipitation membranes shows a conspicuous dependence of the permeabilities on the pH‐values of the fluid phases. A hypothetical model to explain this effect is discussed.
E.M.F. and Calorimetric Investigations of Antimony Oxides
Authors: Knauth P. , Schwitzgebel G.
Published: March 2014

Thermodynamic data of the antimony oxides were determined by solution calorimetry in molten NaOH/KOH (483 K), drop and differential scanning calorimetry and solid state electrochemistry. The formation of Sb2O4 from Sb2O3 and Sb2O5 is an exothermic process (ΔR H (483 K.) = — 25 ± 4 kJ/mol). The molar heat capacity data of the antimony oxides are discussed in comparison with the different CP functions of the literature. The Gibbs free energies of formation at 873 K of Sb2O3 (—472 ± 5 kJ/mol) and Sb2O4 ( — 570 ± 10 kJ/mol) are consistent with calculated values from data compilations.
Structure Determining Interaction in Liquids — An Investigation of Bromobenzene by X‐Ray and Neutron Diffraction Experiments
Authors: Bertagnolli H. , Engelhardt T. , Chieux P.
Published: March 2014

X‐ray and neutron diffraction experiments on liquid bromobenzene are reported. After usually applied data reduction and evaluation the intramolecular contribution was separeted from the total intensity and the intramolecular structure in the liquid phase was determined. The combination of X‐ray and neutron differential cross sections permits an assignment of intermolecular distances to specific atom pairs. With this identification a two‐dimensional model is deduced. A quantitative calculation gives a refined model, reproducing both X‐ray and neutron data. The structure of the first coordination sphere is determined by strongly attractive forces between the bromine atom and the phenyl ring as well as a specific attraction of bromine atoms themselves leading to a characteristic distribution of distances.
Correlation Properties of Vibrational Energy Levels of CO2
Authors: Jost Rémy , Delon Antoine , Pebay‐Peyroula Eve
Published: March 2014

We calculate the statistical correlation properties and the eigenvalues of the potential energy surface of CO2 and observe a smooth change of the NND from Poisson to Wigner distribution between 20000 and 30000 cm−1.
Molecular Beam Study of Ethyl Nitrite Photodissociation and Unimolecular Decay of Ethoxy Fragments
Authors: Felder Peter , Keller Beat A. , Effenhauser Carlo S.
Published: March 2014

The UV photodissociation of ethyl nitrite at excitation wavelenghts of 350, 248 and 193 nm was studied by photofragment translational spectroscopy in a pulsed molecular beam. At all three wavelengths the first dissociation step yields nitric oxide and ethoxy radicals, accompanied by a considerable release of translational energy. At 350 nm the ethoxy radicals are formed with internal energy low enough to be stable under collisionless conditions. At 248 and 193 nm significant fractions of the ethoxy radicals emerge with sufficient internal energy to decay spontaneously into formaldehyde and methyl radicals. At 248 nm a kinematic analysis of the photofragment arrival time distributions is consistent with a sequential dissociation mechanism.
Photodissociation of H2O2/D2O2 from the Lowest Excited State: The Origin of Fragment Rotation
Authors: Klee S. , Gericke K.‐H. , Comes F. J.
Published: March 2014

In order to elucidate the photofragmentation dynamics of small non‐planar molecules, hydrogen peroxide was prepared in its first excited electronic state, Ã1A. The variety of scalar (internal state distribution, translational energy) and vectorial (angular distribution, rotational alignment, correlations between rotational and translational motion) properties of the resulting hydroxyl radicals was analysed by LIF‐Doppler and ‐polarisation spectroscopy. The influence of the upper state repulsive potential and of initial parent vibrational excitation on final product rotation was determined by using deuterium peroxide and internally cold parent molecules.
Dissociation Kinetics of Benzene Van‐der‐Waals Cluster Ions
Authors: Kiermeier A. , Ernstberger B. , Neusser H. J. , Schlag E. W.
Published: March 2014

Benzene clusters (C6H6)n are produced in a supersonic jet expansion and ionized by two‐photon absorption in a reflectron time‐of‐flight mass spectrometer. Cluster ions are produced with a small amount of energy (several hundred meV) and a slow decay on the us time scale is observed. The reflectron mass spectrometer serves as an instrument for the direct observation of all major dissociation paths of clusters near threshold. The precursor ion mass and the daughter ion mass can be assigned unambiguously by the analysis of kinetic energy. In particular the unimolecular fragmentation pathways of benzene cluster ions up to n = 7 are displayed. It was found that close to the dissociation threshold, the elimination of one neutral benzene monomer is the favoured process.
Fe/Mn Oxide Catalysts for Fischer‐Tropsch Synthesis Part VIII: Surface Characterization of Fe/Mn‐Fischer‐Tropsch Catalysts by Auger‐Electron‐Spectroscopy
Authors: Hess D. , Papp H. , Baerns M.
Published: March 2014

Surface compositions of Fe/Mn‐oxide Fischer‐Tropsch catalysts were determined by AES. Bulk compositions of the samples varied from pure iron oxide to pure manganese oxide. A method for quantification of Auger spectra was developed. The iron content in the surfaces of the samples after calcination and reduction is larger than in the bulk. The surface composition after FT synthesis depends on the temperature of reduction before synthesis. The results of surface analysis of the calcined and reduced samples are compared with those of adsorption measurements described elsewhere.