bluuebunny/crossref_metadata_2025_split huggingface dataset:
Massenspektrometrische Untersuchungen an Kupfer‐ und Silberhalogeniden IV: Die Systeme AgxCu1 ‐xCl (0 ≤x≤ 1) und AgClxBr1 ‐x(0 ≤x≤ 1)
Authors: Bernauer Otto , Busse Bernd , Weil Konrad G. 
Published: September 2012

AbstractIn einem Knudsenzellen‐Massenspektrometer wurden die Dämpfe über den Mischungen CuxAg1‐xCl und AgClxBr1‐x(0 ≤x≤ 1) unter‐sucht. Besonderes Interesse galt den Trimeren Cu3Cl3, Cu2AgCl3, CuAg2Cl3, Ag3Cl3, Ag3Cl2Br, Ag3ClBr2und Ag3Br3. Für diese Spezies wurden Auftrittspotentiale und Ionisierungskurven gemessen und die Zerfalls‐Schemata der Primärionen aufgestellt. Aus den relativen Intensitäten konnten die Gleichgewichtskonstanten der Reaktionenmagnified imagebestimmt werden. In beiden Fällen ergibt sichK= 9 ± 2. Die Reaktionsenergien der Prozessemagnified imagenehmen mit wachsendemydeutlich ab, während sie für die Reaktionenmagnified imageim Rahmen der Meßgenauigkeit identisch und vonyunabhängig sind. Fragmentierungen nachmagnified imagekönnen ebenfalls beobachtet werden, die Reaktionsenergien nehmen vony= 0 nachy= 2 ab. Fragmentierung, bei der AgCl2als neutrales Produkt auftritt, findet nur beiy= 3 statt und erfordert deutlich höhere Energie. ‐ Die Ergebnisse werden unter Verwendung der Elektro‐negativitäten der beteiligten Elemente diskutiert.
An EPR study of shock‐wave effects on amethyst and iron‐doped quartz
Authors: Jakubith M. , Lehmann G. 
Published: September 2012

AbstractOriented plates of quartz crystals with iron contents near 100 ppm were loaded with shock pressures between 10 and 55 GPa. Only the least anisotropic EPR signals of Fe3+ were observable after the shocks and were used to assess the increasing disorder of the quartz lattice. Substitutional Fe3+ showed a linear decrease of spin‐lattice relaxation time with shock pressure. Signals from interstitial Fe3− disappeared completely at the pressure limit of dynamic transformation to stishovite. A broad and isotropic EPR signal at a g‐factor of 2.16 is formed as a result of the shock loading and is tentatively assigned to broken bonds. They must be present in clusters of sizes which grow with shock pressure. Measurements of magnetic susceptibility yield a Curie‐Weiss temperature of 3.5 K for these paramagnetic defects.
On the Photopotential Output of Electrochemical Solar Cells Based on Layer‐Type d‐Band Semiconductors
Authors: Tributsch H. , Gerischer H. , Clemen C. , Bucher E. 
Published: September 2012

AbstractA comparative study of molybdenum‐ and tungsten‐dichalcogenides in contact with various redox electrolytes revealed that in absolute values as well as in relation to the energy gap, n‐type WSe2 is producing the largest photopotential output. It exceeds 0.55 Volt in presence of several redox couples (Fe2+/3+, H2Q/Q pH = 10, Fe(CN)3‐/4‐, 6, Ru3‐/4+, Br−/Br2, Ce3+/4+) and amounts to more than 0.7 Volt in presence of I−/I2. Addition of small quantities of iodide can increase the photopotential output in presence of redox systems with lower redox potential by up to 0.1 Volt. This gives further evidence for the specific photochemical surface activity of iodide on layer‐type electrodes and is an example for the influence of surface states on the efficiency of energy conversion. ‐ The higher photopotential output of WSe2 as compared to that of MoSe2 (maximum value I−/I2:0.56 Volt) is explained in terms of a negative shift of the conduction band edge. With respect to the efficiency of electrochemical solar energy conversion WSe2 is considered to be the most promising compound among layer‐type d‐band semiconductors.
Studies of Dye Photooxidation at Semiconductor Electrodes Using Attenuated Total Reflection Techniques
Authors: Spitler M. , Lübke M. , Gerischer H. 
Published: September 2012

AbstractThe technique of attenuated total reflection spectroscopy has been introduced into the study of photooxidation of organic dyestuffs adsorbed at semiconductor electrodes. Using a ZnO electrode itself as the internal reflection element, an internally reflected laser beam served simultaneously as the actinic radiation and as a measuring beam to monitor the absorption of the adsorbed dye layer. Correlation of these data with the photocurrent produced by oxidation of the dye yielded a measure of the quantum efficiency, Φ, for photooxidation of the adsorbed dye. The dye‐semiconductor system rose bengal‐ZnO was studied to demonstrate the capabilities of this technique.
Fluorescence Spectra of Matrix Isolated Ag and Ag2
Authors: Leutloff D. , Kolb D. M. 
Published: September 2012

AbstractFluorescence from silver atoms and dimers isolated in noble gas matrices has been studied at various matrix temperatures. The fluorescence spectra of isolated silver atoms usually show broad emission bands with large Stokes shifts, which are explained by the formation of an exciplex between excited Ag and the matrix cage. In Ar an additional, very narrow and intense fluorescence band from Ag is observed, which is strongly and reversibly temperature dependent. This tine is assigned to light emission from the Ag 4d95s2(D5/2) state, similar to Au, where such an inner‐atomic relaxation is clearly detectable. Emission yield spectra indicate that in a mixture of matrix isolated Ag and Ag2 an effective energy transfer takes place which causes dimer fluorescence after monomer excitation. The fluorescence spectra of Ag in the various noble gas matrices and their temperature dependence are briefly discussed in terms of a model developed for noble gas excimers.
The Electrostatic Potential and the Distribution of Small Ions in Polyelectrolyte Solutions
Authors: Westra S. W. T. , Leyte J. C. 
Published: September 2012

AbstractWithin the framework of the cell model for polyelectrolyte solutions, the Poisson‐Boltzmann equation is solved numerically for polyelectrolyte systems with counterions of different valencies and in the presence of salts of low molecular weight. — Numerical results are used for a discussion of various counterion binding concepts, based on either the electrostatic potential, the counterion distribution function or a critical polyion charge density. From this analysis it appears that for the present systems the use of these concepts leads to unsatisfactory results. For the evaluation of physical properties of the small ions the use of the complete distribution functions are to be preferred instead.
The Thermodynamics of the Hydrogen Bonding of 2‐Amino‐pyri(mi)dine with cis‐Lactams
Authors: Hopmann Rudolf F. W. 
Published: September 2012

AbstractThe thermodynamics of the hydrogen bonded hetero‐association of 2‐amino‐pyridine and 2‐amino‐pyrimidine with the three cis‐lactams γ‐butyrolactam, δ‐valerolactam, and ϵ‐caprolactam in cyclohexane as well as with 1‐isobutyl‐6‐methyl‐uracil in benzene was studied by u.v. absorption spectroscopy. The enumeration of the data was based on the 1:1 stoichiometry by taking into account the lactam iso‐association in terms of the familiar dimerization process.
Solubility of Hydrogen in Alcohols
Authors: Brunner E. 
Published: September 2012

AbstractThe solubility of hydrogen in ethanediol‐1,2, propanol‐1, propanol‐2,2‐methoxyethanol, butanol‐1, butanol‐2,2‐methylpropanol, 2‐ethoxy‐ethanol, pentanol‐1, hexanol‐1,2‐butoxyethanol, and 2‐ethylhexanol‐1 was determined at 25,50, and 100°C and, in general, at up to 100 bar. The error of measurement is estimated to be less than ±2%.
Charged Particles in Sooting Flames I. Determination of Mass Distributions and Number Densities in C2H2‐O2 Flames
Authors: Homann K. H. 
Published: September 2012

AbstractA combination of a nozzle beam sampling system with a simple mass discriminator (mass range 50 to 105 mass units) is described which allows to determine the mass distributions and number densities both of positively and negatively charged soot particles in low pressure flames. The application to slightly sooting C2H2 ‐ 0, flames shows that a strong increase in ionization at the start of the soot forming zone is associated with a soot particle growth from a few hundred to about 2000 mass units. Ionizing soot particles can be distinguished from heavy hydrocarbon ions originating in the oxidation zone. Charged soot particles are smaller on the average than uncharged ones. The maximum number density of charged particles is strongly correlated to the amount of soot formed in the flame. The ionization potential of small soot particles is estimated to ∼5 eV.
Master Equations for Photochemistry with Intense Infrared Light
Authors: Quack Martin 
Published: September 2012

AbstractFour master equations are formulated for unimolecular reactions induced by collisions, by blackbody radiation, by intense, incoherent, quasimonochromatic infrared radiation and by coherent, monochromatic infrared radiation. The relationship between these equations is discussed and the fundamental differences which are due to the different structures of the rate coefficient matrix are pointed out. The properties of the solutions of these equations are investigated in some detail for both time dependent and time independent rate coefficient matrices. A systematic method for determining all the characteristic parameters (eigenvalues, characteristic populations and characteristic times) of the master equations from experimental data or numerical calculations is proposed. A model for the parametrization of the rate coefficient matrix in the master equation for unimolecular reactions induced by monochromatic infrared radiation (URIMIR) is put forward, which uses only easily measurable molecular parameters. The implications of this model for spontaneous infrared emission of highly excited polyatomic molecules are considered. The limitations of the use of intensity proportional rate coefficients (phenomenological cross sections) for optical excitation in URIMIR are pointed out. The determination of the steady state characteristics in URIMIR from experimental data is discussed. In particular, a simple, new method for obtaining the steady state rate constant from measurements of the product yield as a function of laser energy fluence is presented and illustrated with the first evaluation of rate constants for the IR‐photodissociation of several molecules from published experimental data of other authors. The intensity dependence of the rate constant in URIMIR is predicted to be nonlinear and nontrivial in the limit of both low and high radiation intensities. The reducibility of the rate coefficient matrix for URIMIR is considered and the consequences for the interpretation of experimental data are illustrated.
An Isothermal Flow Calorimeter for Pressures to 600 bar
Authors: Heintz A. , Lichtenthaler R. N. 
Published: September 2012

AbstractAn isothermal flow calorimeter is described suitable for measuring enthalpies of reaction and the composition dependence of enthalpies of mixing at high pressures. With the calorimeter, endothermic and exothermic processes can be studied from 5 to 70 C and from 1 to 600 bar. Experimental results are reported for the excess enthalpy HE for n‐hexane with cyclohexane and methanol with water at 298.15 K and various pressures. The pressure dependence of HE is discussed and compared with results available in the literature and those obtained indirectly from the temperature dependence of the excess volume VE at various compositions.
High Temperature — High Pressure Apparatus for Neutron Diffraction on Fluids: Structure Factor of Expanded Fluid Rubidium
Authors: Freyland W. , Hensel F. , Gläser W. 
Published: September 2012

AbstractThe paper describes a new experimental set‐up for neutron scattering experiments on fluid systems at high temperatures and pressures. This technique has been applied for the investigation of the static structure factor S(Q) of expanded fluid rubidium up to 1970 K and 150 bar. The first results obtained up to these conditions show a strong decrease of the intensity of the first peak in S(Q) and a pronounced increase of the scattering at small angles with reducing densities. Within experimental errors no shift in the position of the first peak is found above 900 K. These observations together with the corresponding behaviour of the Fourier transform of S(Q) indicate, that with expansion the distance of nearest neighbours changes only a little, whereas the number of nearest neighbours decreases by about a factor of two, if the density is reduced from 1.2 g cm−3 at 900 K to 0.6 g cm−3 at 1970 K. It is the first time that such a change in the microscopic structure has been studied experimentally for a fluid metal over a wide range of temperatures and densities. The correlation between the increase in S(O) and the change in the mean interatomic interaction is briefly discussed.
A Theoretical Study of the Photoelectron Spectra of GeS, GeSe, and GeTe
Authors: Weinberger P. , Wimmer E. 
Published: September 2012

AbstractThe valence x‐ray photoelectron spectra of GeS, GeSe, and GeTe are investigated theoretically by means of solid state clusters using the scattered wave method. For GeTe relativistic and non‐relativistic energy band structures are calculated in terms of the KKR method. It is found that the characteristic features of the photoelectron spectra for the germanium chalcogenides under investigation can be interpreted sufficiently well on the basis of the cluster calculations. For GeTe, however, relativistic corrections to the cluster one‐electron energies seem to be indispensable.
The Temperature Dependence of the Properties of Electrolyte Solutions. III. Conductance of Various Salts at High Concentrations in Propylene Carbonate at Temperatures from − 45°C to + 25°C
Authors: Barthel J. , Gores H. J. , Schmeer G. 
Published: September 2012

AbstractSpecific conductances of Et4NPF6, Pr4NPF6, Bu4NPF6, LiPF6, KPF6, LiClO4, and KSCN in propylene carbonate were studied at high concentrations in the temperature range from +25°C to ‐45°C. Data are fitted by a least‐squares method to a four‐parametric empirical equation, yielding the maximum specific conductance κmax and the corresponding concentration μ. Within the frame‐work of a hydro‐dynamic model the Stokes‐radii of the ions and the solvent viscosity are found to be the most important conductance‐determining parameters, affecting both κmax and μ Ionic association in solutions with propylene carbonate as the solvent is not of significant importance. Kinetic treatment of conductance yields temperature‐dependent activation energies, but at any one temperature equal for all salts at concentration μ.
Reactions of Molecules in Defined Vibrational States VII. Absolute Rate Determination for the Reaction of D‐Atoms with Vibrationally Excited H2‐Molecules
Authors: Kneba M. , Wellhausen U. , Wolfrum J. 
Published: September 2012

AbstractUsing a discharge‐flow reactor and energy transfer from laser excited HF molecules we have directly measured, that the rate of the reaction D + H2 increases by a factor of 4.104 at 298 K after single quantum vibrational excitation of the H2 molecule. Substantially smaller rate enhancements are predicted by presently available quasiclassical and quantum calculations using the most accurate ab initio potential energy surface.
Electron Transfer between Phenothiazine and Iron(III) in Micellar Systems [1, 2]
Authors: Pelizzetti Ezio , Pramauro Edmondo 
Published: September 2012

AbstractThe effect of different surfactant‐forming micelles on the electron transfer reaction between phenothiazine and iron(III), giving rise to phenothiazinium cation radical, has been investigated by means of a stopped‐flow spectrophotometric technique. In cationic and non‐ionic micelles, the reaction rates are strongly decreased, the main paths taking place in the aqueous phase as well as at the water‐micelle interface (this last path has a specific rate constant 2  3 orders of magnitude lower than in homogeneous phase). In anionic micelles, the reaction rate is sharply increased (up to four orders of magnitude in respect to homogeneous phase) reaching a maximum near to the critical micellar concentration. The reaction progresses in micellar phase as well as at micelle‐water interface. The binding constants of phenothiazine with the different surfactants have been estimated.
Thermodynamische Untersuchungen am System Kobalt‐Nickel. Massenspektrometrische Aktivitätsmessungen in der flüssigen und festen Phase und Berechnung des Schmelzdiagramms
Authors: Tomiska J. , Nowotny H. , Erdélyi L. , Neckel A. 
Published: September 2012

AbstractSowohl für die flüssige als auch für die feste Phase des Systems Co‐Ni wurde zur Ermittlung der freien Zusatzenthalpien ΔGE, der Mischungswärmen ΔHEund der thermodynamischen Aktivitätenaidie Knudsen‐Effusionsmethode in Verbindung met einem Massenspektrometer herangezogen. Die Auswertung der massenspektrometrischen Messungen erfolgt nach einem analytischen Verfahren, das von dem Näherungsansatz für die thermodynamischen Zusatzfunktionen von Redlich und Kister ausgeht. Die erhaltenen thermodynamischen Aktivitäten weisen sowohl für die flüssige als auch für die feste Phase geringfügig negative Abweichungen vom Raoultschen Gesetz auf. Sowohl für die flüssige als auch für die feste Phase sind im gesamten Konzentrationsbereich die Mischungswärmen positiv und die freien Zusatzenthalpien negativ. Für flüssige Legierungen bei 1800 K beträgt das Maximum von ΔHE= 425 J · mol−1(54 At% Ni) und das Minimum von ΔGE= ‐630J · mol−1(49 At% Ni). Für feste Legierungen bei 1600 K beträgt das Maximum von ΔHE= 660 J · mol−1(55 At% Ni) und das Minimum von ΔGE= ‐550 J · mol−1(47, 25 At% Ni).  Unter Verwendung der in der vorliegenden Arbeit ermittelten Werte für die thermodynamischen Zusatzfunktionen und unter Heranziehung von Literaturdaten für die Schmelz‐ und Molwärmen wurde das Schmelzdiagramm von Co‐Ni nach einer allgemein anwendbaren Methode zur Berechnung der Gleichgewichtskonzentrationen koexistierender Phasen ermittelt. Die Methode beruht auf dem verallgemeinerten Newtonschen Verfahren zur numerischen Lösung von Gleichungen.
Thermodynamic and Kinetic Principles of Mass Transfer Separation Processes
Authors: Sawistowski H. 
Published: September 2012

AbstractStarting from the definition of a separation process the need is shown for introduction of a separation concept which is independent of the mechanism of the process and of its boundary conditions. This concept has to be converted into hardware by the introduction of performance factors which depend on the process mechanism and hence on mass transfer kinetics. General equations for mass transfer are presented incorporating concentration, pressure, force and thermal diffusion. Examples of interaction of the different types of diffusion are presented for the separation of binary mixtures and this is followed by a more detailed consideration of special cases of concentration diffusion including a need for model formulation of interphase mass transfer. It is further shown that mass transfer processes can be intensified by thermodynamic methods (modification of equilibrium conditions) or by kinetic methods (introduction of a chemical reaction or change from continuum to molecular level of organisation of matter). Finally, it is shown that alternatives exist for process selection in which energy savings have to be balanced against increased plant complexity.
Selektiver Stofftransport durch Membranen
Authors: Woermann D. 
Published: September 2012

AbstractEine der Voraussetzungen für den Einsatz von Membranen bei Trennverfahren ist die Kenntnis ihrer Transporteigenschaften. Diese lassen sich am geeignetsten durch die Bestimmung der Matrix der phänomenologischen Transportkoeffizienten der linearen Ansätze der Thermodynamik irreversibler Prozesse für das betrachtete Membransystem charakterisieren. Die Methode wird an einem einfachen Membransystem erläutert. ‐ Um gezielt Membranen mit bestimmten Transporteigenschaften herstellen zu können, ist es wichtig, den Zusammenhang zwischen Membranstruktur und Transporteigenschaften zu verstehen. Zur Verdeutlichung dieses Gesichtspunkts werden Membranmodelle diskutiert, die einen Einblick in die physikalischen Ursachen der selektiven Membranpermeation geben.
Selektivität synthetischer Membranen gegenüber Alkali‐ und Halogenid‐Ionen in der Hyperfiltration
Authors: Gunkel M. , Pusch W. 
Published: September 2012

AbstractDie aus Hyperfiltrationsexperimenten mit Alkalichlorid‐ und ‐nitratlösungen sowie Natriumhalogenidlösungen ermittelten Transport‐parameter der phänomenologischen Beziehungen der Thermodynamik irreversibler Prozesse für eine starke Kationenaustauscher‐, eine asymmetrische Polyamid‐ und eine integrierte Polyurethan‐Membran sowie unterschiedlich getemperte asymmetrische Celluloseacetat‐Membranen liefern Näherungswerte für die Verteilungs‐ und Diffusionskoeffizienten der einzelnen Salze in den Membranen. Für die asymmetrischen Celluloseacetatmembranen nimmt der Verteilungskoeffizient der Alkalichloride in der Reihenfolge CsCl < RbCl < KCl ⋍ LiCl < NaCl zu, während sich für die Alkalinitrate kein eindeutiger Gang ergibt. Für die CK‐1‐Membran, eine starke Kationenaustauscher‐Membran, ändert sich die normierte Salzpermeabilität Ps/d (d = effektive Membrandicke) entsprechend dem Waldenschen Produkt Λ · η Die Verteilungskoeffizienten der einzelnen Salze und die auf die effektive Membrandicke normierten Salzpermeabilitäten Ps/d können mit der freien Hydratationsenthalpie ΔGhy der Kationen oder Anionen der entsprechenden Salze korreliert werden.
Conductance and Selectivity of the Lowest Conductance State of the Alamethicin Pore in Lipid Bilayer Membranes
Authors: Hanke Wolfgang , Boheim Günther 
Published: September 2012

AbstractThe polypeptide antibiotic alamethicin forms ion permeable pores in lipid bilayer membranes which exhibit several distinct conductance states being not integral multiples of each other. The pore seems to consist of several molecules which arrange in a barrel stave like structure thus forming a pore of variable diameter.High resolution experiments now show the existence of a further conductance state at ≃ 20 pS in 1 M KCl solution which is ≃ 20% lower than the gramicidin A pore conductance [1]. Whereas alkali cations pass through this lowest alamethicin pore state, it could not be observed (resolved) in case of Tris. H+ and Ca+ +. Conductance and selectivity properties of alamethicin pore states are compared with those of the gramicidin A pore. The relation between pore state conductances and corresponding diameters estimated from sterical model considerations is discussed.