bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of a Scanning‐Kelvinprobe in the Investigation of Electrochemical Reactions at the Metal/Polymer Interface
Authors: Stratmann M. , Wolpers M. , Streckel H. , Feser R. 
Published: July 2012

AbstractIt is possible to measure the work‐function of polymer coated materials with a Kelvin‐probe. In a humid atmosphere this work‐function is mainly given by the corrosion‐potential of the metal substrate. The use of a scanning Kelvinprobe then allows to map the corrosion potential of polymer coated material with a local resolution of approx. 20 μm and to follow the delamination of polymer coatings as well in the vicinity of defects as on metal substrates, which are contaminated at the metal/polymer interface. Simultaneously, the diffusion of oxygen can be followed with a high local resolution after a jump of the oxygen activity within the gas phase.—The same techniques are used to analyse intrinsic defects within monomolecular LB‐films. In a dry gas phase the Volta potential map corresponds to the distribution of dipole‐potentials and therefore allows to distinguish between covered and uncovered parts of the substrate, as the ordered LB‐film shows rather large dipole‐potentials. In a humid atmosphere the Volta potential map again is dominated by the corrosion potential of the substrate and therefore the delamination of the LB‐film in the vicinity of defects can be studied as well as the stability of the film on the metal substrate far away from any defect.
Buildup of Ultrathin Multilayer Films by a Self‐Assembly Process: II. Consecutive Adsorption of Anionic and Cationic Bipolar Amphiphiles and Polyelectrolytes on Charged Surfaces
Authors: Decher G. , Hong J. D. 
Published: July 2012

AbstractWe have recently reported on the consecutive physisorption of anionic and cationic bipolar amphiphiles onto charged surfaces, adsorbed out of aqueous solutions [1]. Here, we extend our previous concept to multipolar compounds such as polyelectrolytes. In contrast to the bipolar amphiphile system, it is not necessary to separate single charges by a rigid unit, when the polyelectrolyte is adsorbed from sufficiently concentrated solutions. In this case the physisorbed layer does not bind with all ionic groups to the surface and exposes free ionic groups at the new film/solution interface. Therefore a polyelectrolyte layer can replace a layer of bipolar amphiphiles in the consecutive buildup of a multilayered assembly. The buildup of multilayers can then be described as follows: A solid substrate with a positively charged planar surface is immersed in the solution containing the negatively charged bipolar amphiphile, a monolayer of the amphiphile is adsorbed and due to its bipolar structure the surface charge is reversed. After rinsing in pure water the substrate is immersed in the solution containing the positively charged polyelectrolyte. Again a monolayer is adsorbed but now the original surface charge is restored. By repeating both steps in a cyclic fashion alternating multilayer assemblies of both compounds are obtained. In the same way multilayer assemblies can be prepared by using negatively charged polyelectrolytes and positively charged bipolar amphiphiles. It is demonstrated that multilayer films composed of at least 39 consecutively alternating layers, which corresponds to a total film thickness of 151 nm, can be assembled.
Semiconducting and Metallic States in Conducting Organic Low‐dimensional Materials
Authors: Schmeißer D. , Bätz P. , Göpel W. , Jaegermann W. , Pettenkofer Ch. , Wachtel H. , Jimenez‐Gonzales A. , Von Schütz J. U. , Wolf H. C. , Taborski J. , Wüstenhagen V. , Umbach E. , Erk P. , Meixner H. , Hünig S. 
Published: July 2012

AbstractFilms of conducting organic materials can be prepared in either a metallic or a semiconducting state as will be demonstrated for polymeric and crystalline films of polypyrrole and of DCNQI salts, respectively. The specific features of each state are described by the electronic structure of the materials near the Fermi level which is deduced from electron spectroscopies. Further, the transitions between these different conduction states are shown to be based on different mechanisms.
Mobility of Ionic Space Charges in Thin Insulating Films
Authors: Kluger K. , Lohrengel M. M. 
Published: July 2012

AbstractThe anodic oxide formation on high‐purity aluminium electrodes in an acetate buffer of pH 5.9 has been studied by potentiostatic pulse measurements. When the field strength E is low, the concentration of mobile charge carriers is close to zero. When the field strength is increased, ions are transferred through the phase boundaries forming vacancies or ions at interstitial sites to guarantee a sufficient ionic conductivity of the oxide. Using multiple pulse measurements the presence and the dwell time of the mobile charge carriers can be monitored. The modifications of the conventional high field model are described. At low field strength the injected mobile charge carrier concentration decreases exponentially with waiting time.
Measurement of Chemical Resonance by Multiplexing a Chemical Steady State
Authors: Münster A. F. , Schneider F. W. 
Published: July 2012

AbstractA new method for the measurement of chemical resonance is presented. In the proposed “multiplex”‐procedure a chemical focus in a CSTR (Continuous – Flow – Stirred – Tank – Reactor) is perturbed by superimposing flow rate noise on the steady state. The resonance frequency of the focus is determined from its normalized power spectrum. The multiplex method does not provide precise information about the absolute value of the damping constant since the response is a finite time series of transients and not a free induction decay as measured in NMR, for example. The “scanning” method, which measures stationary response amplitudes at various frequencies should be used for the precise determination of the damping constant.
Quantum‐Classical Mixed Mode Analysis of Nonlinearly Coupled Oscillators: A Time‐Dependent Self‐Consistent‐Field Approach
Authors: Yurtsever E. , Brickmann J. 
Published: July 2012

AbstractA two‐dimensional vibrational system with a strong nonlinear coupling is studied using a quantum‐classical mixed mode self‐consistent‐field approach. The classical equations of motion as well as the time‐dependent Schrödinger equation are solved for respective modes under the influence of the average fields generated by the other modes. This vibrational system was previously shown to be chaotic under classical mechanical treatment but quantum mechanical observations pointed out to highly regular behaviour. The results of the mixed mode calculations give periodic trajectories, regular Poincare maps and Lyapunov numbers, k = 0. These observations support the previous findings that during the transition from classical to quantum mechanics, regularity dominates the dynamical behaviour.
Kinetics of the Reaction of OH Radicals with CH2CO
Authors: Oehlers C. , Temps F. , Wagner H. Gg. , Wolf M. 
Published: July 2012

AbstractThe kinetics of the homogeneous gas phase reaction OH + CH2CO → products (1) has been investigated at room temperature and pressures between 1.4 mbar ≤ p ≤ 2.5 mbar using the discharge flow method. Reactors with Teflon wall coatings and with different surface‐to‐volume ratios were employed to exclude effects of heterogeneous reactions. OH radicals were generated via the reaction F + H2O. Their concentration‐versus‐time decay profiles were followed under pseudo‐first‐order conditions, [CH2CO] → [OH]0 with a Far Infrared Laser Magnetic Resonance (FIR‐LMR) spectrometer. The rate constant of the title reaction was found to be k1, (296 K) = (7.2 ± 2.0)·1012 cm3/mol·s.
X‐Ray Diffraction Measurements for Expanded Fluid Selenium up to the Supercritical Region
Authors: Tamura Kozaburo , Hosokawa Shinya 
Published: July 2012

AbstractThe X‐ray diffraction measurements for fluid Se have been carried out in the temperature and pressure range up to 1500°C and 815 bar. We have developed a new type of high‐pressure vessel and a new sample cell made of single‐crystal sapphire for the X‐ray diffraction measurements using the energy‐dispersive method. We have obtained the structure factor and the pair distribution function as functions of temperature and pressure. From the detailed analysis of the pair distribution function we conclude that the twofold coordinated structure is largely preserved in the region where the optical gap disappears and the progressive increase of conductivity becomes evident. On the basis of the findings we speculate on the existence of the small chain molecule with the planer zig‐zag conformation which may cause the transition to the metallic state in fluid Se.
Photochromic Response of Vacuum‐Evaporated Nb2O5 Thin Films in Ethanol Vapor
Authors: Yao J. N. , Loo B. H. , Hashimoto K. , Fujishima A. 
Published: July 2012

AbstractAmorphous Nb2O5 thin films are obtained by vacuum evaporation of high‐purity Nb2O5 powders onto NESA glass substrates. These films were found to exhibit both photochromism and electrochromism. Reasonably good photochromic responses were observed in ethanol and in the N2 atmosphere, but no photochromism was observed in the air or in a pure O2 atmosphere.
Comparison between the Photo Induced Chemical Reaction in the NO2 – C2H4 van der Waals Complex and the O + C2H4 Gas Phase Reaction
Authors: Loison J. C. , Dedonder‐Lardeux C. , Jouvet C. , Solgadi D. 
Published: July 2012

AbstractThe photodissociation of NO2 within NO2–C2H4 complexes or small clusters excited at 355 and 266 nm leads to the formation of vibrationally and rotationally cold vinoxy radicals (CH2CHO). On the other hand, the vinoxy radicals produced in gas phase thermal collisions are vibrationally and rotationally hot. Comparison between these experiments seems to show that two different competitive reaction paths are responsible for the different internal energy content in the vinoxy radical.
Strong Bipolar Electrokinetic Charging of Thin Liquid Jets Emerging from 10 μm PtIr Nozzles
Authors: Faubel M. , Steiner B. 
Published: July 2012

AbstractIn a very thin liquid jet of pure water which flows with high speed into a vacuum chamber we observe unexpectedly large streaming currents and electrokinetic charging. This potential shift at the liquid surface is interfering with planned photoelectron spectroscopy. It is quantitatively studied as a function of the jet flow rate, the electric dissociation and the pH value of the fluid. The standard electrokinetic model and a nonequilibrium electrochemical diffusion current model are discussed for a semiquantitative explanation.
Shell Structure in Photoionization Spectra of Trivalent Metal Clusters
Authors: Pellarin M. , Lermé J. , Baguenard B. , Broyer M. , Vialle J. L. , Perez A. 
Published: July 2012

AbstractPhotoionization mass spectra of large AlN and InN clusters, produced by laser vaporization technique, have been recorded via standard TOF spectroscopic methods. Ionization potentials are measured in the size range N = 37–112 for aluminum and N = 31–132 for indium. Comparison between these two trivalent simple metals is presented, as well as with the electronic shell structure predictions of the spherical jellium model. In the large size range N = 200–1400, regular oscillations are observed in the AlN mass spectra. This oscillating behaviour, which is a manifestation of the electronic shell structure of the Ne = 3N valence electrons, is analyzed within the semiclassical theory of single‐particle quantum level density. The oscillation period as a function of Ne3, two times shorter than the period obtained in alkali cluster experiments, is well explained by the classical two‐turn star orbit contribution, whereas for alkali metals the electronic structure near the Fermi energy is governed by the single‐turn triangular and square orbit contributions.
Influence of Microsolvation on the Molecular Dynamics: Structure‐Dependent Intramolecular Vibrational Redistribution Process in the Benzene‐Arn Heteroclusters
Authors: Schmidt Martin , Mons Michel , Calvé Jacques Le 
Published: July 2012

AbstractRecent two‐color R2PI spectroscopic results combined with Monte Carlo simulations have shown that the first benzene‐Arn clusters exhibit a large variety of isomeric forms: one‐sided and two‐sided conformers as well as two different one‐sided isomers for the Bz–Ar3 complex. Taking advantage from the existence of these different arrangements of argon “solvent” atoms around the Bz molecule, the influence of the microsolvation characteristics on the dynamical properties of the clusters has been investigated: in particular the occurrence of intramolecular vibrational energy redistribution (IVR) in the S1 state. The results presented on the first Bz–Arn clusters (n ≤ 3) show that the IVR process is not only n‐dependent, but also, within a well‐defined complex, strongly isomer‐dependent.
High Temperature Reactions of Phenylacetylene
Authors: Herzler J. , Frank P. 
Published: July 2012

AbstractHydrogen atom abstraction from phenylacetylene (C6H5‐C2H) like its reaction with hydrogen atoms have been studied at elevated temperatures behind reflected shocks. ‐ The unimolecular decomposition of very low initial concentrations (3 ‐ 22 ppm) of phenylacetylene was investigated in the temperature range 1600 to 1900 K by monitoring the temporal H‐atom production. ‐ For C6H5‐C2H + H, the thermal decomposition of very low concentrations (1 ‐ 3 ppm) of C2H5I served as H‐atom source. Atomic resonance absorption spectrometry (ARAS) was used to record simultaneously H‐atom and I‐atom profiles. The experiments covered the temperature range 1190 to 1530 K. ‐ For both series of experiments, the total pressure was about 2.3 (+/‐0.3) bar.For the unimolecular reaction R1: C6H5‐C2H → C6H4‐C2H + H a rate constant expression of: magnified image was found.For the bimolecular reaction R2: C6H5‐C2H + H → products a rate constant of: magnified image was deduced.From the available thermochemical data two product channels have to be discussed: magnified image Detailed evaluation of existing thermodynamic data enables the calculation of an equilibrium constant for reaction R 2a. From this and under the assumption that reaction R 2a is the dominant product pathway at elevated temperatures, a rate constant expression of magnified image is deduced for the reaction of phenyl readicals with acetylene, which is an important process in sooting flames: magnified image This rate constant agrees within a factor of 2 with the data from recent studies executed by Fahr et al. [1a, 1b].
Elementary Reactions in the Methanol Oxidation System. Part I: Establishment of the Mechanism and Modelling of Laminar Burning Velocities
Authors: Grotheer Horst‐Henning , Kelm Siegfried , Driver H. S. T. , Hutcheon R. J. , Lockett R. D. , Robertson G. N. 
Published: July 2012

AbstractA set of combustion relevant rate coefficients recommended by a group of European kineticists has been tested by calculating laminar burning velocities. Virtually without any adjustments, a good match with experimental data has been achieved for H2/CO/air flames, H2/CO/air flames, and CH4/air flames. In order to extend this set by inclusion of the reactions forming the CH3OH oxidation subsystem, the current knowledge of these reactions if first reviewed. The extended set yields calculated burning velocities for CH3OH/air flames in good agreement with measurements recently obtained under stretch free conditions. By using a sensitivity analysis, the remaining deficiencies of the model are highlighted and it is made clear where further experimental work is particularly needed.
Stabilization of Premixed, Conical Methane Flames at High Pressure
Authors: Eberius H. , Kick Th. 
Published: July 2012

AbstractA new high pressure burner has been designed and built in order to investigate stationary, premixed flames at high pressure. The burner exhibits several unique features such as modular design, small dimensions, excellent optical access for spectroscopic measurements, provisions for the use of probes, a system for accurate flow and pressure control, and various safety devices. The operating pressure regime could be raised in successive stages up to the present 100 bar. Methane/air flames have been stabilized in this pressure regime as flat flames on porous disc burners and as conical flames above nozzle burners. The very small conical high pressure flames showed regular shape and good stability in the fuel rich regime. Thus, it was possible to derive from the cone angle burning velocities, which agree favourably with model calculations.
Dielectric Relaxation of Aqueous Electrolyte Solutions II. Ion‐Pair Relaxation of 1:2, 2:1, and 2:2 Electrolytes
Authors: Barthel J. , Hetzenauer H. , Buchner R. 
Published: July 2012

AbstractThe low‐frequency relaxation process contributing to the complex permittivity spectra of aqueous solutions of MgSO4, CdSO4, Na2SO4, CdCl2, and CuCl2 is investigated. The dispersion amplitudes are analysed with the help of model calculations, based on a modified Cavell equation for ellipsoidal bodies. It is shown that ion pairs are responsible for the low‐frequency relaxation process with solvent separated ion pairs dominating for the sulfates, whereas contact ion pairs are formed by the chlorides. The observed relaxation time is analysed as the superposition of chemical and reorientational relaxation. For the ion pairs the effective volumes of rotation and the rate constants of formation are determined. The results are compared with information from the literature.
Dielectric Studies of Butyl Chloride Solutions
Authors: Jadżyn J. , Kȩdziora P. , Bonnet P. 
Published: July 2012

AbstractThe results of dielectric polarization and non‐linear dielectric effect studies for three isomers of butyl chlorides in solutions are presented. It is shown that in the systems of weak molecular interactions the shape of molecules is the main factor which determines the dielectric properties of solutions.
The Specific Heat of Butoxyethanol/Water Critical Mixtures
Authors: Würz U. , Grubič M. , Woermann D. 
Published: July 2012

AbstractResults of measurements of the specific heat capacity of n‐butoxyethanol/water and iso‐butoxyethanol/water of critical composition as function of temperature are reported. Both systems have in common that in the vicinity of the critical temperature aggregates of butoxyethanol molecules and concentration fluctuations with unusual long range correlations (critical amplitude ξ0+ ≈︁ 0.4 nm) coexist. The analysis of the data shows that both systems belong to the same universality class as “simple” binary mixtures. The value of the critical amplitude ratio of specific heat capacity (A/A+) and the value of the critical exponent α are consistent with the predictions of the Landau‐Ginzburg‐Wilson model (d = 3, n = 1). The same is true for the value of the amplitude ratio RA,ξ+ calculated from the specific values of the critical amplitudes ξ0+ and A+.
X‐ray Investigation of Supercooled Water
Authors: Corban R. , Zeidler M. D. 
Published: July 2012

AbstractX‐ray diffraction curves were measured for water at – 20°C, – 10°C, –5°C in the supercooled region and in addition for comparison at +4°C and + 30°C. The data were corrected for polarization and absorption, Compton scattering was completely included. Evaluation was based on molecular form factors and the molecular center correlation function was obtained. A continuous change of the pair correlation function from the normal to the supercooled region is found, all peak amplitudes increase with decreasing temperature and the first peak shifts in position. Comparisons with available literature data on deuterated water and with computer simulation results on ST2‐water are presented.
Solution of Hydrogen in Cold‐Worked Pd‐Ag Alloys
Authors: Kishimoto Shozo , Yoshida Noritetsu , Yao Takeshi , Itani Tsukasa , Flanagan Ted B. 
Published: July 2012

AbstractThe effect of annealing temperature on hydrogen solubilities in the dilute region (α phase) has been investigated for cold‐worked Pd‐Ag alloys containing from 5 to 40 atomic % Ag by measuring pressure‐composition isotherms between 273 and 348 K. These data have been correlated with changes in physical properties arising from the recoveries of lattice defects during annealing between 373 and 1073 K. It is found that the magnitude of the solubility enhancements for the alloys having the same degree of cold‐working decreases with increasing Ag content reaching zero at 40 atomic % Ag; this result suggests that the dislocation densities in Pd‐Ag alloys do not lead to concomitant solubility enhancements.
Fast Processes in UV‐Two‐Photon Excitation of Pare Liquids
Authors: Sander Martin , Brummund Uwe , Luther Klaus , Troe Jürgen 
Published: July 2012

AbstractDecomposition and ionization reactions of neat liquid alkanes, alcohols, water, and halomethanes after UV‐two‐photon absorption were investigated by pump‐and‐probe measurements with subpicosecond time resolution. Previous suggestions are revised and new mechanisms proposed which consistently explain the transient absorption signals obtained. In particular, it is shown that the importance of free or “quasi‐free” electrons as intermediates in the photodecomposition of liquids has commonly been largely overestimated.
Thermodynamics of Ammonium Halopallidates II. Heat Capacity and Thermodynamic Properties of (ND4)2PdCl6 at Temperatures from 5 K to 325 K
Authors: Callanan Jane E. , Weir Ron D. , Westrum Edgar F. 
Published: July 2012

AbstractThe heat capacity of deuterated ammonium hexachloropallidate (ND4)2pDCl6 was measured from 5 K to 325 K by adiabatic calorimetry. One λ‐shaped phase transition, absent in the protonated salt, was found in the curve for heat capacity against temperature. This transition reaches its maximum Cp.m ≃ 150 · R at (30.2 ± 0.1) K with ΔtrsSm0 = (2.005 ± 0.009) · R (R = 8.31451 J · K−1 · mol−1) and marks the change from the high temperature cubic structure to the low temperature tetragonal structure. The Debye temperature at 0 K equals (96.5 ± 2.4) K and below 10 K, only lattice vibrations make significant contributions to the heat capacity. Smoothed values of the standard thermodynamic quantities for pure (ND4)2PdCl6 are tabulated up to 320 K and the Sm0(273.15 K) = (49.80 ± 0.05) · R.
The Chemical Bond in Amorphous Solids: Localization on Continuous Random Networks
Authors: Koslowski Th. , Von Niessen W. 
Published: July 2012

AbstractWe report numerical results for localization induced by disorder on continuous random networks. The density of states and localization properties of simple tight‐binding Hamiltonians are computed. A scaling method is used to decide about the localized or extended character of eigenstates. For a model system in two dimensions and for models of amorphous Si and Ge, the influence of electron localization on transport properties is discussed. The localization properties are interpreted from a quantum chemical point of view, using the concept of population analysis.