bluuebunny/crossref_metadata_2025_split huggingface dataset:
CO2 Laser Chemical Vapor Deposition of Amorphous Silicon: Gas Phase Processes and Thin Film Properties
Authors: Golusda E. , Lühmann K.‐D. , Mollekopf G. , Stafast H. , Wacker M. 
Published: July 2012

AbstractCW CO2 laser CVD of a‐Si:H was performed in a parallel configuration of the substrate and a horizontal CO2 laser beam. During deposition in situ gas analysis was performed by sampling through an orifice in the substrate surface (Ts = 400 °C) using a molecular beam and mass spectrometry. Time resolved measurements revealed a start‐up period of several minutes. Its influence onto the a‐Si:H film quality was investigated with respect to the dark and photo conductivities, optical band gap, fermi level, hydrogen bonding in SiH and SiH2 groups, density of defects in the mobility gap, and Urbach energy.
The Phase Behaviour of Amphiphilic Monolayers
Authors: Peterson I. R. 
Published: July 2012

AbstractAmphiphilic monolayers display a wealth of condensed phases. It is only recently that these have been widely recognised as being distinct, but they are in fact quite analogous to the well‐known lamellar gel phases of bulk lyotropic and thermotropic mesogens. An understanding of these phases has proved to be important for controlling the defect structure of the monolayers used in the fabrication of Langmuir‐Blodgett films. This understanding is being achieved by developments in a number of techniques, including X‐ray diffraction and isotherm miscibility. The phase diagrams of the materials studied so far are all very closely related, lending new credibility to the principle of corresponding states, which although proposed on many occasions, has not until now received much in the way of quantitative confirmation.
On the Electrostatic Component of the Adhesional Interaction between Solid Substrates and Langmuir Monolayers
Authors: Riegler Hans , Eugel Maria 
Published: July 2012

AbstractThe work of adhesion between Langmuir monolayers and solid surfaces in a hydrophilic Langmuir‐Blodgett configuration has been measured as function of the surface charge densities σ of the contacting surfaces. It was derived from the equilibrium meniscus height which was measured with the transfer fluorescence microscope. The surface charge density of the contacting surfaces was varied by changing the subphase pH. With both surfaces negatively charged (dimyristoylphosphatidylethanolamine onto SiO2‐substrates) and low charge densities (σ < 1 e−/100 Å2)) we observe a decrease of the adhesion with increasing charge density. At high charge densities (dimyristoylphosphatidic acid onto SiO2‐substrates, σ < 1 e−/100 Å2) the work of adhesion is hardly affected by charge density variations, as theoretically predicted for electrostatic double layer forces. Systems with only one surface of varying negative charge density (dipalmitoylphosphatidylcholine onto SiO2) unfold the predicted decrease of the work of adhesion with increasing charge density. Control experiments with varying pH and uncharged surfaces (dipalmitoylphosphatidylcholine onto polymethylmethacrylate surfaces) show a pH‐independent work of adhesion and thus corroborate that the measured behaviour is caused by the electrostatic double layer interaction.
Scanning Tunneling Microscopy of the Initial Stages of Metal Condensation on Semiconductor Surfaces Progress Report
Authors: Brodde A. , Harazim E. , Kliese R. , Röttger B. , Neddermeyer H. 
Published: July 2012

AbstractAfter a brief description of the theoretical and experimental basis of scanning tunneling microscopy (STM) typical results from the initial stage of metal condensation on semiconductor surfaces will be presented. As substrates Si(111) and Si(100) are used. Their reconstruction is explained by the current atomic models and compared with STM images of the clean surfaces. While the 7 × 7 reconstruction of Si(111) can be prepared with a defect concentration in the order of 0.03% of a monolayer, Si(100) shows a higher density of imperfections by at least one order of magnitude. STM images from nonreactive systems (Ag/Si(111) and Ag/Si(100)) are described and from a reactive system (Fe/Si(111)), which forms well defined silicides. In case of Ag/Si and room temperature condensation the initial stage is characterized by a two‐dimensional interface layer, which does not cover the substrates completely and the growth of rather regular three‐dimensional Ag islands, whose shape is consistent with metallic character. After Fe deposition on Si(111) the surface is covered by islands, which due to their irregular size and shape indicate compound formation or intermixing with Si. After annealing Fe/Si(111) shows the development of well ordered Fe silicide layers.
Time Evolution of :CF2 in the IR Multiphoton Dissociation of CF2Cl2: RRKM Considerations
Authors: Chowdhury Pradyot Kumar 
Published: July 2012

AbstractThe CO2 laser induced multiphoton dissociation of CF2Cl2 takes place in atomic and molecular chlorine elimination channels, with about 8% of the reaction by the latter channel. Time resolved experiments show a fast formation of :CF2 from the primary reaction, followed by a secondary slow growth from the decomposition of CF2Cl. The experimental rates are consistent with the RRKM rate constants with an excitation energy of nearly 343 kJ/mol in CF2Cl2. At high laser fluences, addition of argon has improved the dissociation yield, due to rotational hole filling mechanism. The internal energy of CF2Cl2 decreases from 356 to 343 kj/mol on addition of argon as buffer gas. The nascent vibrational temperature of the CF2 is 950 K, whereas an overall temperature of the thermalized ensemble in milliseconds time is computed to be 480 K.
Cationic Self‐Diffusion in the Metastable Ionic‐Plastic Phase of CH3NH3Br Studied by 1H NMR
Authors: Tansho Masataka , Nakamura Daiyu , Ikeda Ryuichi 
Published: July 2012

AbstractThe plastic nature of the highest‐temperature metastable phase of CH3NH3Br obtainable above 483 K was studied by X‐ray diffraction, differential scanning calorimetry, and 1H NMR spin‐lattice and spin‐spin relaxation time measurements. The CsCl‐type cubic structure determined for this phase implies the presence of highly disordered cationic orientations in accordance with the reported results in the other ionic‐plastic crystals. 1H NMR relaxation times observed in this phase were well explained by the motional model of the slow translational self‐diffusion and rapid overall rotation of the CH3NH3+ cations. The obtained activation energy (51 kJ mol−1) and correlation times (1.1 · 10−8 s at the melting point) were shown to be reasonable values as compared with those in stable plastic crystals. The melting condition derived from the dynamic parameters obtained in molecular and ionic plastic crystals was generally discussed.
Interactions in Dodecylammonium Chloride/Dodecyl Sulfate Systems
Authors: Filipović‐Vinceković N. , Škrtić D. , TomaŠić V. 
Published: July 2012

AbstractPhase boundaries for mixtures of dodecylammonium chloride (DDACl) and sodium dodecyl sulfate (NaDS) are determined over a wide range of concentrations. The phase behavior strongly depends on the molar ratio and concentration of surfactant present. In the range of concentrations where monomer‐micelle equilibrium prevailed the mixed micelles of different composition are formed. The addition of oppositely charged surfactant enhance the apparent degree of counterion dissociation (α). Results reveal the existence of asymmetry on NaDS‐rich systems; more pronounced shift of CMCNaDS with DDACl addition, higher increase of αNa values and the two regions of mixed micelles formation. The deviation of precipitate‐solubility boundary from linearity is explained by phase transitions from precipitate and coacervate to mixed micelles. The concentrations at which coacervate is formed are lower than it would be found in the absence of DDADS.
A Characterization of the Aliphatic/Hydroxyl Interactions using a Group Contribution Model (Disquac)
Authors: Gonzalez J. A. , Garc Fuente I. ÍA De La , Cobos J. C. , Casanova C. 
Published: July 2012

AbstractThe data available in the literature for the molar excess Gibbs energiesGE, azeotropes, molar excess enthalpiesHE, activity coefficients γi∞, and partial molar excess enthalpiesHiE,∞, at infinite dilution, and molar excess heat capacitiesCpE, of n‐alkan‐1‐ol (1) + n‐alkane (2) mixtures are examined on the basis of the DISQUAC group contribution model. Being available the interaction parameters for systems containing methanol or ethanol, we report the interchange coefficients from propanol to hexadecanol:Cah.1DISandCah,1QUAC(1 = 1,2 or 3). For the dispersive coefficients:Cah,1DISincrease with the size of the n‐alkan‐1‐ol;Cah,3DISdecrease as far as propanol, and then increase regularly, an opposite behaviour is encountered forCah,3DISthe quasichemical coefficients:Cah,1.DISandCah,3.DISare constant, andCah,3CUACvaries in a similar way to the maximum of theHEof the mixtures under study; from decanol, they are constant. The model describes consistently the molar excess functions for the systems investigated, even theCpEand, qualitatively, the temperature dependence of this magnitude. Partial molar excess quantities at infinite dilution are reasonably well represented. Larger differences are obtained forH1E,∞.
Comment on the Low Lying Singlet States of Acenaphthene
Authors: Swiderek Petra , Hohlneicher Georg 
Published: July 2012

AbstractIn the absorption spectrum of acenaphthen the onset of the second singlet transition is obscured by a strong overlap of the S1and the S2band. Comparison of absorption spectra taken in solution and in the gas phase allows an identification of the 0–0 transition of S2through the different solvent shift of S1(120 cm−1) and S2(1200 cm−1). The gas phase spectrum is shown up to 48000 cm−1.
Analysis of the Phase Diagrams of Mixtures of a Nematic Liquid with n‐Alkanes
Authors: Orendi H. , Ballauff M. 
Published: July 2012

AbstractThe complete phase diagrams in liquid range of mixtures of the nematic liquid crystal 4,4′‐azoxyanisole (PAA) with n‐dodecane, n‐octadecane, and n‐tetracosane have been determined. The experimental results are analyzed quantitatively in terms of a theory based on the Flory lattice model of nematic fluids. It is shown that all features present in the experimental phase diagrams are in accord with the theoretical predictions. Nearly quantitative agreement of theory and experiment can be reached if a concentration‐dependent interaction parameter is used to describe the isotropic interaction between the nematic liquid crystal and the dissolved n‐alkane.
Electrochemical Analysis of Anomalous Conductivity Effects in the AgClAgI Two Phase System
Authors: Lauer Ute , Maier Joachim 
Published: July 2012

AbstractThe overall conductivity of the system AgCl/AgI is studied and distinct anomalies are found in the miscibility gap (Ag+‐conductivity enhancement up to 1.5 orders of magnitude). An impedance spectroscopic investigation accompanied by studies of phase diagram and microstructure proposes two main conclusions: i) the conducting interfacial pathways are composed of homo‐ (AgX/AgX) and hetero‐(AgX/AgX′) contacts, both exhibiting enhanced conductivities (compared to AgCl and β‐AgI bulk). ii) Both pathways are characterized by vacancy conduction in the relevant space charge layers.
The Phase Diagram of the Quasiternary System (ZnkCd1–k)(SelTl1–t)
Authors: Leute Volkmar , Wulff Birgit 
Published: July 2012

AbstractThe Phase Diagram of the Quasiternary System (ZnkCd1–k)(SelTe1–l) in the temperature region 800 K ≤ T ≤ 1300 K is investigated by X‐ray measurements and by electron microprobe analysis. Experimental results concerning the miscibility gap between phases with zincblende and wurtzite structure and concerning the spinodal miscibility gap within the zincblende region are compared with calculations of the equilibrium tie line fields based on a four particle cluster model. – Moreover, calculated distributions of cluster probabilities are used to explain special features of the phase diagram.
Solubility of Hydrogen in Palladium‐Yttrium‐Silver Alloys
Authors: Sakamoto Y. , Ishimaru N. , Inoue Y. 
Published: July 2012

AbstractThermodynamic quantities for absorption of hydrogen by Pd95–xYxAg5 solid solution alloys with up to x = 6.3 at.% Y have been determined from measurements of pressure‐composition isotherms at temperatures between 273 K and 473 K and hydrogen pressures up to 1000 Torr. The hydrogen absorption characteristics have been compared with those of the previously reported Pd–Ag and Pd–Y binary alloys. The relative partial molar enthalpy, ΔHH0, at infinite dilution of hydrogen in Pd95–xYxAg5 alloys increases in exothermicity with increasing Y content from that of Pd–5.0 at.% Ag, almost parallel to that in Pd–Y binary alloys. The relative partial molar entropy, ΔSH0, at infinite dilution in the ternary alloys decreases with Y content from that of Pd–5.0 at.% Ag alloy. The hydrogen solubility behavior at low hydrogen concentration in the Pd–Y–Ag alloys under a “constant volume” condition can be described as due to mainly the strong H–Y attractive pair interaction in the Pd host lattice. The stability of β‐hydride and hydrogen concentration at αmax phase boundary increase following alloying with Y from that of Pd–5.0 at.% Ag alloy, respectively, and the changes in the properties with Y content are similar to that in Pd–Y binary alloys.
e Effect of Alkyl Groups on Carbanion Stability Part I. Interaction of Small Rings with Adjacent Carbanion Centers
Authors: Balcioǧlu Nurettin , Sevin Fatma , Evin Özden , Peynircioǧlu N. Bekir 
Published: July 2012

AbstractRelative kinetic acidity measurements have shown that the cyclobutyl group has the ability to stabilize an adjacent carbanion center similar to vinyl and cyclopropyl groups, although to a lesser extent. The results of semiempirical calculations (MNDO) covering all the mentioned substituents, including the isopropyl group correlate well with the experimentally determined relative kinetic acidities.
Multinuclear Spin‐Lattice Relaxation Studies of Undercooled Aqueous Potassium Fluoride Solutions Under High Pressure
Authors: Radkowitsch H. , Lang W. 
Published: July 2012

AbstractIn this investigation we report2H,1H and19F spin‐lattice relaxation (SLR) rate experiments performed in undercooled aqueous KF‐solutions of concentrationc≤ 12 molal under an external pressure ofp≤ 225 MPa. The relaxation rate curves of the various nuclei are consistently interpreted with a two mode – two site approximation of the dynamic structure of the H‐bond network in these ionic solutions. The local arrangement of water molecules coordinated to an F−‐anion can be obtained from Fluor‐19 relaxation rate curves and is found to correspond to an almost linear ion‐water configuration. This finding is in accord with predictions from theory and computer simulations and corrects earlier findings from other NMR experiments.
Gas Phase Reactions of Transition Metal Clusters
Authors: Riley S. J. 
Published: July 2012

AbstractThe chemical reactions of isolated clusters of transition metal atoms with small molecules will be reviewed. Reactions of iron, cobalt, and nickel clusters with hydrogen, ammonia, water, and nitrogen will be considered. Experiments which determine the uptake of adsorbate molecules vs. reagent gas pressure provide information on kinetic and equilibrium processes, as well as a measure of the number of adsorbate binding sites on a cluster's surface. More detailed, quantitative determinations of reaction rate constants often show dramatic variation of reactivity with cluster size. Equilibrium studies provide measurements of cluster‐adsorbate binding energies. A knowledge of the number of adsorbate binding sites often provides information about cluster geometrical structure.
Reactions of Alkali‐Halide Clusters
Authors: Whetten Robert L. , Homer Margie L. , Li Xiuling , Livingston Frank E. , St. John Pamela M. , Beck Rainer D. 
Published: July 2012

AbstractThis article reviews recent experimental work on reactive processes involving alkali‐halide clusters (AHC). The processes discussed include: adsorption of molecules on AHCs [1]; reactive collisions of alkali‐fluoride clusters with silicon surfaces [2]; and the primary photochemistry of alkali‐bromide and ‐iodide clusters [3,4]. Earlier work on evaporation and cleavage processes, and experiments on clusters with excess electrons, are not reviewed.
Chemical Reactions in Clusters Induced by Low Energy Electrons
Authors: Hashemi Reza , Jaffke Thomas , Illenberger Eugen 
Published: July 2012

AbstractElectron attachment reactions in pure CF4 clusters and heterogeneous clusters composed of CF2Cl2 and O2 are studied. In the system CF4, effective energy randomization leads to the formation of CF monomers which occurs through dissipation of several electronvolts of excess energy among the target aggregate. From the mixed clusters, ions of the form ClO and ClO− are generated. ClO− is the result of a complex scattering reaction in the ionized aggregate associated with the cleavage of two chemical bonds and the formation of a new molecule.
Fragmentation Analysis of Size Selected Sodium Clusters
Authors: Bewig L. , Buck U. , Mehlmann Ch. , Winter M. 
Published: July 2012

AbstractWe investigate the fragmentation behaviour of size selected sodium clusters Nan, n ≤ 4, for different ionization methods. The experimental technique, size selection by means of scattering the cluster beam from a helium target beam and subsequent time resolved measurement of the scattered particles, enables us to find a unique correlation between the detected cluster ions and their neutral precursors. In the case of photoionization we use the light from a Xe‐arc lamp in a broad spectral range down to a wavelength of about 220 nm, whereas for the pulsed, frequency doubled dye laser the wavelength is tuned to 290 nm. Electron impact ionization has been examined with an electron energy of 25 eV, which is far above the ionization threshold of all sodium clusters. The ionization by electron impact with the large excess energy results in a total fragmentation of the sodium trimer. In the case of photoionization the fragmentation probabilities do not follow always the energetically favoured pathways, which will be demonstrated for the sodium tetramer.
Clusters of Divalent Elements: Electronic Properties of Cdx‐Aggregates
Authors: Rademann K. , Ruppel M. , Kaiser B. 
Published: July 2012

AbstractWe have recently succeeded in generating and detecting neutral cadmium clusters Cdx (x < 80) in a seeded supersonic molecular beam. The mass spectrometric abundances of photoionized clusters exhibit remarkable intensity variations. There are large intensity ratios for Cd10/Cd11 as well as Cd20/Cd21 indicating the closing of electronic shells with 20 and 40 electrons. The photoelectron spectra of neutral cadmium clusters show the formation and filling of shells, indeed. Discrete electronic states (2s2) have been observed directly in the photoelectron spectra of mass specified Cd10 clusters. Pronounced electronic shell closings are also clearly observed for clusters with 70 electrons (Cd35), 92 electrons (Cd46, and 138 electrons (Cd69). Furthermore, we have obtained quantitative information on the size dependence of ionization potentials and photoionization cross sections. The ionization potentials (7.7 ± 0.1 eV for the dimer Cd2 and 5.0 ± 0.1 eV for Cd46) decrease rapidly but rather smoothly with increasing cluster size.
The ZEKE Spectrum of the Phenol‐Water Cluster
Authors: Dopfer Otto , Reiser Georg , Lindner Reiner , Müller‐Dethlefs Klaus 
Published: July 2012

AbstractThe vibrational spectrum of the hydrogen bonded phenol‐H2O cation cluster is obtained by two‐colour resonant pump‐probe ZEKE spectroscopy (“Zero Kinetic Energy” Photoelectron Spectroscopy). The results are a well resolved vibrational spectrum assigned to intermolecular modes and an accurate value of the adiabatic ionisation energy.
Theoretical Interpretation of Optical Response Properties of Simple Metal Clusters
Authors: Bonačić‐Koutecký V. , Fuchs C. , Pittner J. , Koutecký J. 
Published: July 2012

AbstractThe ab‐initio configuration interaction study of excited states of small alkali metal clusters accounts fully for the spectroscopic patterns recorded by depletion or/and femtosecond spectroscopy and permits geometrical assignment. Specific structural and electronic properties responsible for excitations in small Ia/IIa clusters allow for the interpretation of theoretical and experimental findings in the framework of a molecular many‐electron description. Similarities and differences between optical response properties of Lin and Nan clusters are discussed. The influence of the position of a divalent heteroatom in the geometrical structures of NaxMg clusters on spectroscopical patterns will be presented. The reliability of simplified methods such as random phase approximation (RPA) and multiconfigurational linear response method (MCLR) for optically allowed transitions in metal clusters has been examined.
Time‐resolved TPI‐Spectroscopy of the B‐ and D‐State of Na3‐Clusters
Authors: Schreiber E. , Kühling H. , Kobe K. , Rutz S. , Wöste L. 
Published: July 2012

AbstractThe dynamical behaviour of excited states of cold Na3‐clusters in the gas phase was investigated in a transient two‐photon‐ionization (TPI)‐experiment, employing picosecond pump technique followed by mass‐selective detection. The results exhibit for the first time the pseudo‐rotational motion of the B‐state as a temporal sequence. The precise measurement of the beat frequencies affirms a pseudo‐Jahn‐Teller‐model for the interpretation of the spectroscopic data. For the D‐state, known to predissociate very rapidly the temporal evolution of fragmentation directly could be observed. Decay‐times of the TPI‐signal were estimated to be in the order of 5 picoseconds.
Elementary Reactions in the Methanol Oxidation System. Part II: Measurement and Modeling of Autoignition in a Methanol‐Fuelled Otto Engine
Authors: Driver H. S. T. , Hutcheon R. J. , Lockett R. D. , Robertson G. N. , Grotheer Horst‐Henning , Kelm Siegfried 
Published: July 2012

AbstractThe temperature inside the cylinder of a methanol‐fuelled single‐cylinder research engine running under knocking conditions is measured by means of Coherent Anti‐Stokes Raman Scattering (CARS) spectroscopy, and the pressure is measured with a piezoelectric transducer. In order to obviate any errors arising from possible deficiencies in the spectral scaling laws which are commonly used to represent nitrogen Q‐branch CARS spectra at high pressure, a purely experimental technique is employed to derive temperatures from CARS spectra by cross‐correlation with a reference library of spectra recorded in an accurately calibrated high‐pressure high‐temperature optical cell. — The temperature and pressure profiles measured in the running engine are then used as input data for chemical kinetic modeling of the endgas autoignition. Exactly the same exhaustive chemical mechanism and exactly the same rate coefficient expressions are used for the autoignition modeling as are employed in Part I [1] for the modeling of methanol flame velocities. A good qualitative understanding of the mechanism underlying endgas autoignition in the engine can be obtained, although the calculated autoignition point occurs slightly earlier than the observed point. — The importance in the autoignition mechanism of hydroperoxyl radical reactions and of the thermal decomposition of hydrogen peroxide is demonstrated by means of a sensitivity analysis. – For purposes of comparison, the autoignition modeling is also undertaken using earlier reaction schemes and rate coefficient data, notably those of Grotheer and Kelm (1989), Norton and Dryer (1989), Esser and Warnatz (1987), and Dove and Warnatz (1983). The discrepancies between results of the various models can be understood in terms of a very small number of sensitive reactions for which there are conflicting kinetic data.