bluuebunny/crossref_metadata_2025 huggingface dataset:
A note on multiplicity of the steady state and oscillation‐phenomena in catalytic oxidation
Authors: Riekert L.
Published: July 2012

Multiplicity of the steady state is to be expected if thermodynamics permits the existence of a metal as well as that of an oxide on the surface of a catalyst in contact with the reactants; oscillations in the kinetic regime may result if neither of these two phases is kinetically stable.
Nuclear magnetic relaxation as indicator in oscillating chemical reactions
Authors: Schlüter A. , Weiss Alarich
Published: July 2012

The nuclear magnetic relaxation titrations is applied to study the oxidation of malonic acid with BrO3⊖in the presence of Mn3⊕/Mn2⊕as catalyst. The maximum amplitude of the free induction decay in a 180°‐τ‐90°1H‐NMR pulse experiment is used as a measure for the spin‐lattice relaxation rate 1/T1. Thereby, the oscillating nature of the reaction can be followed up conveniently. It is shown that the reduction Mn3⊕→ Mn2⊕in this reaction is of first order with respect to the concentration of Mn3⊕.
The Heats of Formation of Some Sodium and Barium Vanadates and Molybdates
Authors: Kubaschewski Oswald , Hoster Thomas , Schlim Roger
Published: July 2012

An isoperibol room‐temperature calorimeter has been constructed to measure the spontaneous reactions of BaO and Na2O with MoO3 and V2O5 after ignition. With this calorimeter, the heats of formation from the component oxides have been determined for BaMoO4, BaV2O6, Na2MoO4, Na2Mo2O7, NaVO3, Na4V2O7 and Na3VO4.
Entmischungsverhalten von Ethylen und niedermolekularem Polyethylen
Authors: Spahl Roland , Luft Gerhard
Published: July 2012

The reciprocal solubility of ethylene and polyethylene‐wax was determined at temperatures from 383 to 473 K under pressures up to 200 MPa. Besides the cloud curve, the shadow and the coexistence curves have been measured. The miscibility gap is present in the whole range of concentration for pressures under 65 MPa. The heterogeneous region increases slightly with rising temperature, the critical curve remains practically unchanged with varying temperature. The solubility of ethylene in the polymer could be described with good accuracy on the bases of Henry's law and the theory of Flory‐Huggins for solutions of polymers. This description can be made by means of a simple expression for the temperature and pressure dependency of Flory's parameter. The phase behaviour of the investigated system is compared with experimental measurements and with those of other authors carried out on mixtures with ethylene and alkanes having lower molecular weights.
Reductive and Non‐Reductive Effects of Cosensitizers on the Rhodamine B‐Sensitized Charge Separation at CdS Surface
Authors: Watanabe T. , Takizawa T. , Honda K.
Published: July 2012

Origin for the enhancement effect of hydroquinone (HQ), Fe2+, I−, Br−, and Cl−(cosensitizers) on the efficiency of electron injection from excited rhodamine B (RhB) to CdS has been investigated by combination of photoelectrochemical and heterogeneous photochemical measurements. The results indicate that the enhancement of RhB‐sensitized charge separation by HQ, Fe2+, and I−is due to reductive regeneration of the dye, while that by Br−and Cl−is mainly due to increased RhB adsorption at the CdS/aqueous solution interface.
On the Use of Resonant Raman Intensities and Bond‐Order Calculations to Refine Molecular Force Fields
Authors: Peticolas Warner L.
Published: July 2012

In this paper a theory is presented for calculating the resonant Raman intensities for all 3N‐6 molecular vibrations of a molecule excited by a Π → Π* electronic transition using only the known geometry of the molecule, the force constants (i. e. force field) for the internal coordinates and a molecular orbital calculation of all of the C‐ C and C‐ N bond orders in the ground and excited electronic states. Criteria are presented for the refining of a force field on the basis of observed and calculated resonant Raman intensities. — The method has been applied to 1‐methyl uracil. excited states which occur at 260 nm and 190 nm. The calculated intensities are compared with measured resonant Raman intensities using exciting light at 266 nm, 257 nm, and 212.8 nm. The agreement is satisfactory in that only the observed resonant Raman bands are calculated to have intensity.
Structural Changes in the Retinal Chromophore of Bacteriorhodopsin Studied by Resonance Raman Spectroscopy
Authors: Alshuth Th. , Stockburger M.
Published: July 2012

Resonance Raman (RR) spectra were obtained from aqueous suspensions of the purple membrane of Halobacteria. The RR spectra reflect the photolabile retinal chromophore of bacteriorhodopsin which induces proton translocation across the membrane. RR spectra of the all‐trans chromophore BR570 and its 13‐cis component BR548 were recorded both in H2O and D2O suspension. The vibrational analysis revealed characteristic hydrogen bending modes of the Schiff base linkage by which retinal is bound to the protein. These bands are very sensitive to structural changes of the Schiff base and allow conclusions on geometrical and electronic changes of this group which play an important role in the proton translocation process.
Raman Spectra of Aqueous NaClO4 and NaBF4 Solutions
Authors: Schiöberg D.
Published: July 2012

The OD stretching vibration band in Raman spectra of liquid HOD containing ClO4− or BF4− ions is splitted into two components. The higher frequency band vw is assigned to ODw groups which are weakly H‐bonded to neighbouring anions (A): ODw = (OD... A). In Raman spectra of fully deuterated aqueous NaClO4 or NaBF4 solutions the vw band is splitted once again. The higher frequency band v3, wb is attached to the partially antisymmetric stretching vibration of unsymmetrically H‐bonded D2O molecules with a weak H‐bond at one OD group and a strong H‐bond at the other OD group (= bDODw). The lower frequency band must be assigned to the symmetric stretching vibration of D2O weakly H‐bonded to anions with both OD groups (= wDODw). The bands were separated into Gaussian‐Lorentzian product functions. The OD and D2O concentration were calculated from the band areas.
Kinetics and Mechanism of Hydrocarbon Formation in the System C2H2/H
Authors: Homann K. H. , Schweinfurth H.
Published: July 2012

The formation of C3H4(Propyne and Allene), C4H2(Butadiyne) and also of formaldehyde in the system C2H2/O with and without added H atoms was studied at 298 K and in a pressure range between 1.4 and 8.0 mbar. H atoms have a strongly positive influence on the rates of formation of these species. The results obtained for largely varying initial conditions were described quantitatively by a reaction mechanism of 25 reactions. Experiments with D atoms and with different O2concentrations gave additional evidence of the radical reactions involved.
On the Orientation of Liquid Crystals by Monolayers of Amphiphilic Molecules
Authors: Hiltrop K. , Stegemeyer H.
Published: July 2012

The orientation of nematic liquid crystals (LC) by monolayers of suitable amphiphilic compounds on solid substrates has been studied by systematic experiments using polarizing microscopy, magnetic Freedericksz‐transition, and contact angle measurements. Orientation is influenced mainly by the following parameters: 1. temperature; 2. physical properties of the substrate surface; 3. chemical properties of the substrate surface. Molecular models describing the orientating action of amphiphilic monolayers are developed and discussed in terms of the obtained quantitative results. Changes in LC orientation with film packing density and temperature can be understood as phase transitions of the system “amphiphilic monolayer + embedded LC”.
Interfacial Phenomena of TiO2‐Photoanodes
Authors: Lam R. U. E.'t , Schoonman J. , Blasse G.
Published: July 2012

The small‐signal a.c. response of photoelectrochemical cells with Nb‐doped TiO2 anodes has been studied for frequencies in the range 10−2‐104 Hz. A non‐linear least‐squares analysis of the complex admittance/impedance data leads to a detailed equivalent circuit for the cell. The analysis and results are compared with a recently reported Relaxation Spectrum Analysis [4]. The equivalent circuit contains passive elements, and a constant‐phase‐angle (CPA) element Q = kα(iω)−α. It is shown that a “distribution of relaxation times” model, and a “universal dielectric response” model describe frequency‐dependent elements, which are of the CPA‐form. The space‐charge capacitance in the present equivalent circuit obeys the Mott‐Schottky relation, while the CPA‐element is attributed to current inhomogeneities. Solid state aspects of H2 reduction provide a rationale for the current inhomogeneity model.
Thermodynamics of (1‐Chloronaphthalene + n‐Alkane): Excess Enthalpies, Excess Volumes and Excess Heat Capacities
Authors: Grolier J.‐P. E. , Inglese A. , Roux A. H. , Wilhelm Emmerich
Published: July 2012

A flow microcalorimeter of the Picker design has been used to measure molar excess enthalpies at 298.15 K of the seven binary liquid mixtures 1‐chloronaphthalene + n‐hexane, + n‐heptane, + n‐octane, + n‐decane, + n‐dodecane. + n‐pentadecane, and + n‐hexadecane. Experiments were performed in the discontinuous mode, covering essentially the whole composition range. The overall imprecision of the measurements is characterized by standard deviations from Redlich‐Kister type smoothing equations of generally less than ± 1 per cent of the maximum value HEmax of the excess enthalpy (with respect to mole fraction). The most striking feature is that for 6 ± n ± 16 (n denotes the number of C‐atoms of the n‐alkane) HEmax decreases with increasing n, the correlation being approximately linear. – For the mixtures 1‐chloronaphthalene + n‐hexane, + n‐heptane, + n‐octane, + n‐dodecane, + n‐pentadecane, and + n‐hexadecane molar excess volumes VE at 298.15 K were obtained, as a function of mole fraction, from measurements of the density with a vibrating‐tube densimeter. The excess volumes are negative in all cases and become less negative with increasing chain length of the n‐alkane. At equimolar composition, for (1‐C10H7Cl + n‐C6H14) we find VE = ‐1.555±10−6 m3 mol−1, and for (1‐C10H7Cl + n‐C16H34), VE = ‐0.397±10−6 m3 mol−1. A Picker flow calorimeter was used to determine molar excess heat capacities at constant pressure CEp at 298.15 K for all mixtures except for 1‐C10H7Cl + n‐C10H22, and + n‐C16H34. The excess heat capacity is essentially zero for the mixture with n‐hexane, and increases with increasing chain length up to (1‐C10H7Cl + n‐C12H26); for (1‐C10H7Cl + n‐C15H32), CpE is somewhat smaller, thus indicating a trend inversion.
Effect of Deuterium Substitution on the Vapour Pressure of Acetonitrile
Authors: Jákli Gy. , Koritsánszky T. , Jancsó G.
Published: July 2012

The vapour pressure difference between CH3CN and CD3CN was measured by differential capacitance manometry between – 40 and + 80°C and the results can be expressed by the equation: In (pH/pD) = 871.8K2/T2 – 13.58K/T + 0.00687. The vapour pressure of acetonitrile between the melting point and 30°C has also been determined. The experimental data were interpreted within the framework of the statistical theory of isotope effects in condensed systems. The largest contribution to the vapour pressure isotope effect arises from the shifts in the CH stretching vibrations on condensation and these were found to undergo a blue shift with increasing temperature. The results also indicate that the rotation of the molecules about the 3‐fold symmetry axis can be considered quasi‐free whereas the rotations about the axes perpendicular to the top axis are restricted.
Messung der spezifischen Wärme und des Joule‐Thomson‐Koeffizienten von Kohlendioxid bei Temperaturen von – 40°C bis 200°C und Drücken bis 15 bar
Authors: Bender R. , Bier K. , Manrer G.
Published: July 2012

In order to improve the experimental data for the thermal properties of carbon‐dioxide, the isobaric heat capacity and the adiabatic Joule‐Thomson‐coefficient of carbon‐dioxide have been measured with a flow calorimeter in the temperature range from −40°C to 200°C at pressures up to 15 bar. In the investigated range, the accuracy is better than 0.15 per cent for the heat capacity and 0.5 per cent for the Joule‐Thomson‐coefficient. The isothermal throttling coefficients at zero pressure, obtained by extrapolation of the experimental values, are consistent with the temperature dependence of the second virial coefficient as measured by A. and C. Michels.
A Structural Investigation of Liquid Chloroform
Authors: Bertagnolli H.
Published: July 2012

Starting from neutron scattering experiments on the species CDCl3, CD35Cl3, CD37Cl3 and CHCl3 the expansion coefficients of the generalized pair correlation function g00000(R), g00101(R), g00202(R), and g00110(R) are determined and analyzed quantitatively, thus providing preferred positions and orientations of the molecules in liquid chloroform. From the same set of experimental data the chlorine‐chlorine pair correlation function and the weighted sum of the chlorine‐hydrogen and chlorine‐carbon pair correlation functions are evaluated. The most probable configuration between two chloroform molecules in the liquid phase is derived from the position of the first peak of the corresponding pair correlation function. Both ways of description yield a consistent structural picture; namely the dipole axes are inclined and the hydrogen atoms point into the hollow between two chlorine atoms.
Tracer Experiments on the Exchange Equilibrium of Tritium between Hydrogen Gas and the Hydrogen‐Storage Material TiMn1.5‐Hydride
Authors: Sicking G. , Magomedbekov E. , Hempelmann R.
Published: July 2012

The equilibrium distribution of3H between hydrogen gas and the intermetallic hydrogen storage material Ti0.4Mn0.6Hn, being in equilibrium with the light hydrogen, was determined by tracer experiments in the α‐phase region and in the temperature range from 23°C. to –60°C. The equilibrium separation factors follow the relationshipThe values of the separation factors show up an enrichment of tritium in the solid solution, whereas in the PdHn‐system the opposite observations are made. It is shown that the isotope distribution at higher hydrogen contents is not only determined by energy differences of vibrational states. but may also be influenced by non‐idealities within the solid solution. From the non‐idealities calculated in case of P‐PdH” together with the equilibrium separation factor measured in the P‐phase, a local mode energy of the interstitial hydrogen ofis derived ‐ For Ti0.4Mn0.6Hnin the α‐phase region a value about twice as highturns out, which we confirmed by neutron scattering experiments. From these results H is concluded to occupy interstitial tetrahedral holes in Tio,Mno”H, . ‐ From hydrogen sorption isotherms at low equilibrium pressures, measured in addition to the exchange experiments with a‐Tio,Mno,6H” contributions from “surface hydrogen” are deduced. These contributions are not reflected by the values of the separation factor because of the vibrational frequencies of “surface hydrogen” are similar to those of H in tetrahedral holes. With systems, however, dissolving hydrogen in octahedral positions (as e.g. PdH,), an inversion of the isotope effect is observed going from “bulk”‐ to “surface hydrogen”.
Oxygen Reduction on Transition‐Metal Porphyrins in Acid Electrolyte I. Activity
Authors: van Veen J. A.R , van Baar J. F. , Kroese C. J. , Coolegem J. G. F. , De Wit N. , Colijn H. A.
Published: July 2012

The oxygen reduction characteristics of metalloporphyrins adsorbed at monolayer levels on a high surface area carbon, Norit BRX, have been studied in 8 N H2SO4 and also in 6N KOH. In an acid, oxygen reduction activity is found to be correlated with the MeII/MeIII redox potential. Most Co complexes have too high a redox potential, while too low a redox potential is observed for Fe, Ru, Os, Mn, and Cr. Ir porphyrins have the highest activity. In KOH, Ru porphyrins show the best performance. A heat treatment improves activity and stability strongly in an acid, but only mildly in an alkaline solution. A mechanism is proposed for oxygen reduction on transition metal chelates, both in acid and in alkaline solutions.
Oxygen Reduction on Transition‐Metal Porphyrins in Acid Electrolyte II. Stability
Authors: van Veen J. A. R. , Colijn H. A.
Published: July 2012

The stability of untreated and heat‐treated Co and FeT(p‐OCH3)PP/Norit BRX (T(p‐OCH3)PP = meso‐tetra(p‐methoxy)phenylporphyrin) has been studied under a variety of conditions: in pure electrolyte (6N H2SO4), in the presence of H2O2, and under a current load (O2 reduction); all at various temperatures. It appears that the heat‐treated Co catalyst has adequate stability for most low‐temperature applications (6NH2SO4, T ≤ 60°C, i ≤ 30 mA/cm2).
Einfluß von Tensiden auf Strömung und Stoffübergang in einer flüssig/flüssig‐Kanalströmung
Authors: Ollenik R. , Nitsch W.
Published: July 2012

Measurement of flow and mass transfer were performed in a two‐phase liquid/liquid‐channel arrangement in absence and presence of soluble surface active substances (Sodium‐dodecylsulfate).—Laser‐Doppler‐velocimetry was used to measure interfacial velocities and velocity profiles perpendicular to the interface in the water and in the solvent phase. Mass transfer measurements are related to the transfer of aceton across the plane interface between water and carbontetrachloride. It is shown that below the critical micell concentration (cmc) an almost rigid interface is formed with a highly suppressed mass transfer, near the cmc an increase of mass transfer and interfacial velocities was observed, and above the cmc mass transfer behaviour and interfacial flow is corresponding to an absolutely clean interface.—The compression of the surfactant layer was calculated applying the equation for Newtonian shear stress on the measured flow profiles. The resulting gradients of interfacial pressure are in good agreement with the interfacial pressures, calculated on the basis of the so‐called “cmc‐effect”.
Validity of Macroscopic Concepts for Fluids on a Microscopic Scale
Authors: Alder B. J. , Alley W. E. , Pollock E. L.
Published: July 2012

By Fourier decomposition of the appropriate fluctuation it is possible within the regime of linear response to extend the concept of both thermo‐dynamic quantities and transport coefficients to their dependence on both wavelength and frequency. Experimentally these generalized macroscopic properties are accessible through neutron diffraction and, as examples, the dependence of the sound speed on wavelength and the diffusion coefficient on time are discussed. Through the molecular dynamics computer method the dependence of the viscosity on wavelength is calculated and applied with spectacular success to predict the dependence of the friction coefficient on the size of a Brownian particle all the way to atomic dimensions. On the other hand, the dielectric constant continuum concept, as applied to a charge or dipole in a cavity, generally fails to predict even the correct field at large distance from the charge. Avoiding the introduction of a cavity cures that problem, but the generalized dielectric constant fails badly in predicting the field at shorter distances from the charge.
Transport Properties of Liquids. II. Self‐Diffusion of Almost Spherical Molecules in Athermal Liquid Mixtures
Authors: Vogel Herbert , Weiss Alarich
Published: July 2012

By 1H‐NMR spin‐echo spectroscopy the self‐diffusion coefficients Dte of almost spherical test molecules—Sn(CH3)4, Si(OCH3)4, Ti(OtBu)4, and SnOct4—in the solvents—CCl4, Si(OCD3)4, and Si(O1Pr)4‐d28—were studied as a function of temperature and concentration.—The excess volumes of the mixtures investigated are approximately zero. The measurements show:

If the diameter dte of the test molecule is larger than, or equal to, that of the solvent molecule (dso), Dte∞ (infinite dilution) approaches Dso0.

If dte < dso, then Dte∞ > Dso0.

The activation energy of the self‐diffusion process of the test molecules at infinite dilution approaches the activation energy for the diffusion process of the solvent molecules.

Application of the free‐volume model to the experimental results is quite satisfactory except the situation of large test molecules diffusing in solvents composed of small molecules (dte > dso).
Formation of Clusters in 1‐Propanol/Water‐Mixtures
Authors: Großmann Georg H. , Ebert Klaus H.
Published: July 2012

Very sensitive and accurate elastic light scattering (LS) measurements have been carried out on mixtures of water with methanol, ethanol, 1‐propanol and 2‐propanol. Methanol showed no particular effect, while ethanol, 2‐propanol and 1‐propanol showed signs of increasing cluster formation at a composition of 1 alcohol molecule to 5 water molecules. For the mixture of 1‐propanol with water, additional measurements of the quasielastic light scattering have been made and the hydrodynamic radii of the clusters have been calculated. This led to the suggestion of a cluster consisting of 8 1‐propanol molecules and a solvation envelope of about 40 water molecules. The concentration of this cluster was determined by elastic LS to be 83% of the total solution weight at 25°C and a composition of 40% by weight 1‐propanol in water. The clusters appear to be rather stable, as the hydrodynamic radius showed no significant variation with temperature in the 5° to 50°C range. The concentration was however temperature dependent, as could be shown with elastic LS.
The Mercury Sensitized Photolysis of Tetramethylsilane in the Temperature Range 650 K – 800 K. The Heat of Formation of 2‐Methyl‐2‐Silapropene
Authors: Potzinger P. , Reimann B. , Roy R. S.
Published: July 2012

(CH3)3SiCH2 radicals, formed in the primary process (1)

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decompose according to (4)

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in the temperature range 650 K ‐ 800 K. The activation energy for process (4) has been measured to be 170 ± 8 kJ/mol. This value allows one to calculate an upper limit for the heat of formation of 2‐methyl‐2‐silapropene ΔHf0 ≤ ‐2 kJ/mol which is in very good agreement with other values calculated from literature data and supports earlier findings that the back reaction (‐4) has a negligible activation energy. The combined average from our results and the literature is ΔHf0 ((CH3)2Si = CH2) = 2−13+9 kJ/mol.—Furthermore it is shown that 2‐methyl‐2‐silapropene is more stable than the corresponding silylene and carbene isomers. The ζ bond energy has been estimated to be 189 kJ/mol, in excellent agreement with calculations by Ahlrichs and Heinzmann [20].
Über das magnetische Verhalten von Cs2ASmF6 (A = Na, K, Rb)
Authors: Urland W.
Published: July 2012

The magnetic behaviour of Cs2NaSmF6, Cs2KSmF6 and Cs2RbSmF6 has been studied in the temperature range between 3.0 and 251.3 K. The magnetic data are interpreted by means of a previously developed model in which the influence of the crystal field is theoretically described by the angular overlap model. The angular overlap parameter eπ (R) is determined for given ratio eπ (R)/eπ (R). As basis the 66 state functions of the ground term 6H as well as the 108 state functions of the sextet terms 6H and 6F are used. The dependence of the angular overlap parameters eπ (R) and eπ (R) on the basis is investigated. The energy. The energy values of the crystal‐field levels of the two lowest states 6H5/2 and 6H7/2 are calculated.
Self Diffusion in Carbon Dioxide Near the Critical Point
Authors: Krynicki K. , Meragi A.‐L. , Powles J. G.
Published: July 2012

Measurements of the self diffusion coefficient, D, by the nuclear‐magnetic‐resonance field‐gradient method for carbon dioxide (13CO2) are reported for the coexisting liquid from the triple point to the critical point and for the fluid at the critical density from the critical temperature upwards. No anomaly in D is observed near the critical point and the behaviour is similar to that of other liquids. It seems likely that the previously reported anomalous behaviour (Duffield and Harris, 1976), in 14CO2, measured by the capillary method, is erroneous.
Zum thermischen unimolekularen Zerfall von Methanol
Authors: Spindler K. , Gg. Wagner H.
Published: July 2012

The thermal unimolecular decomposition of methanol was investigated behind reflected shock waves in the temperature range 1600 to 2100 K, using argon as a diluent and monitoring CH3‐ and OH‐absorption signals. —Methanol decomposes in the main channel according to

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The reaction takes place in the fall off region when total densities are varied from 1.1 · 10‐6 to 5.6·10−6 5.6·10‐5 mol/cm3. Using the theory of unimolecular reactions the rate constants

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in the high pressure limit and

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in the low pressure limit could be obtained. A computer simulation of the decomposition of methanol and the consecutive reactions was carried out.
Transformations in Ag2+δS and Ag2+δSe: A Calorimetric Study
Authors: Shukla A. K. , Sen P. , Sarma D. D.
Published: July 2012

Calorimetric studies of transformations have been carried out in single crystals of Ag2+δS and Ag2+δSe of coulometrically controlled compositions. The entropy changes accompanying the α‐β transitions of these solids with different degrees of non‐stoichiometry are discussed in the light of crystal structures and statistical arguments.
Surface Enhanced Raman Scattering of Cyanide Chemisorption Layers on Silver/Electrolyte Interfaces. Part II
Authors: Plieth W. , Roy B. , Bruckner H.
Published: July 2012

The dependence of the surface enhanced Raman signal of CN− ions on silver/electrolyte interfaces at 2114 cm−1 was investigated by varying the laser intensity, the laser frequency, the angle of incidence, and the angle of observation. The Raman signal was also observed on electrolytic deposits of silver on gold substrates.
Capacity and Photocurrent Measurements at Passive Titanium Electrodes
Authors: Schultze J. W. , Stimming U. , Weise J.
Published: July 2012

The capacity and photocurrent behaviour of passive titanium electrodes has been investigated in dependence on the film thickness and the electrode potential, the photocurrents additionally on the wavelength. From capacity measurements a high donor concentration of 1020 cm−3 and a dielectric constant of D = 9 can be concluded. Compared to bulk TiO2 electrodes, the onset of the photocurrent is shifted to higher photon energies. The band gap is estimated to be Eg = 3.4 eV. At constant electrode potential ε the photocurrent decreases with increasing film thickness though the absorption of the film should be higher. This indicates the strong influence of the field strength in the film on the photocurrent which increases with thickness at constant field.
Flash Photolysis in Aqueous Periodate‐Solutions
Authors: Wagner I. , Strehlow H.
Published: July 2012

In the flash photolysis of periodate in the pH‐range 2.44 to 4.90 using conductometric detection three reactions are observed with time constants of the order 10−4 s, 10−2 s and 1 s (at 298 K and pH = 3). The fastest reaction is attributed to the general acid catalyzed hydration reaction of IO−4 to H4IO−6. The two slower reactions are due to the hydrolysis of I2O8 and I2O6. The relative amounts of these latter reactions depend on the concentration of oxygen in the solution. Oxygen atoms formed rapidly by the photolysis of periodate are scavenged by oxygen with the production of ozone. Ozone oxidizes IO3 to IO4 which dimerizes to I2O8.
Photo‐Degradation and Fluorescence of Colloidal‐Cadmium Sulfide in Aqueous Solution
Authors: Henglein A.
Published: July 2012

Colloidal cadmium sulfide deposited on 13 nm silicon dioxide particles shows a weak fluorescence with a maximum at 620 – 660 nm (depending on the sample). Oxygen does not quench the fluorescence. All anions exert a quenching effect at concentrations below 10−3 M, S2‐, Br−, and I− being the most effective ones. Tl+, Ag+, Pb2+, and Cu2+ strongly quench the fluorescence at concentrations below 10−4 M. Nitrobenzene quenches at higher concentrations in the 10−3 M range. Quenching is attributed to adsorbed ions or molecules. In the case of the anions, a mechanism is proposed in which positive hole‐anion pairs are formed at the surface of the colloidal particles before neutralization by electrons takes place. In the case of the cations and of nitrobenzene, quenching is explained by electron capture. Colloidal CdS doped with less than 1% Cu2+ or Ag+ showed a much stronger fluorescence than undoped samples.—Colloidal cadmium sulfide is degraded by light only in the presence of oxygen the quantum yield in aerated solution being 0.04. The action of oxygen is mainly attributed to a reaction with intermediates of the sulfide oxidation by positive holes. In the presence of Tl+ or Pb2+ ions at some 10−5 M, the photo‐degradation is drastically promoted up to a quantum yield of 0.24. Cu2+ and Ag+, however, retard the degradation. Both effects are understood in terms of electron scavenging by the adsorbed metal ions and reoxidation of the reduced metal by oxygen or by positive holes. Sodium sulfide protects cadmium sulfide from degradation. In the absence of air, small amounts of hydrogen are formed in Na2S containing solution.
Dynamics of Simple Gas‐Surface Interaction. I. Rotationally Inelastic Collisions at Smooth Surfaces
Authors: Polanyi J. C. , Wolf R. J.
Published: July 2012

We report a trajectory study of the rotationally inelastic scattering of initially rotationless molecules BC at a smooth (uncorrugated) rigid surface. The potential energy function (p.e.fn.) was either purely repulsive (a “truncated Lennard‐Jones” potential) or embodied a 0.2 eV well. Mass combinations corresponded to N2, CO or HF. Examination of the final rotational state, jf, as a function of initial angle of BC to the surface, xi, showed how the outcome of a gas‐surface encounter altered with a systematic shift in location of the centre of mass of BC, for a given p.e.fn. The changing pattern of rotational rainbows was recorded, and differing types of gas‐surface encounter were analyzed and identified. Introduction of wells in the p.e.fn. gave rise to indirect trajectories, with a consequent reduction in average rotational energy of the BC (CO masses) scattered indirectly. This may have a bearing on the experimentally observed lag of rotational temperature for surface scattered molecules, as compared to surface temperature.
Progress and Prospect in Elementary Reaction Kinetics/Dynamics of Polyatomics
Authors: Kaufman Frederick
Published: July 2012

The present state of knowledge of two‐body elementary reaction rates of polyatomics is examined using five specific reactions as examples: OH + H2 → H2O + H, Cl + CH4 → HCl + CH3, OH + CH4 → H2O + CH3 and nine Cl, F‐substituted CH4 reactions, OH + HNO3 → H2O + NO3, and HO2 + O3 → OH + O2 + O2. For each reaction, experimental and theoretical results are given, and their accuracy is evaluated. Progress in experimental measurements seems to have outrun that in theoretical description. Ab initio quantum chemical calculations of potential energy surfaces, quantum tunneling corrections, and error and sensitivity analyses are greatly needed to improve our understanding of rate parameters.
Analysis of the Resonance in the Three Dimensional F + H2 Reaction
Authors: Wyatt Robert E. , McNutt Joe F. , Redmon Michael J.
Published: July 2012

Quantum mechanical resonance structure in the three‐dimensional F + H2 reaction is analyzed in several ways: wavefunction density and flux maps in the transition state region, Argand diagrams which show the energy variation of S‐matrix elements, the time delay computed from the energy derivative of the phase of S‐matrix elements, and the energy variation of nodes in the product channel translational wavefunctions. In addition, differential cross sections for the v = 0 → v' = 2 reaction, computed from quantum reaction probabilities in an optical model, are compared with experimental data. These results are correlated with other recent theoretical results on this reaction, and some remaining theoretical problems are discussed.
Micellar Properties of 4‐Alkylamido‐2‐Hydroxybenzoic Acids
Authors: Pelizzetti Ezio , Pramauro Edmondo , Barni Ermanno , Savarino Piero , Corti Mario , Degiorgio Vittorio
Published: July 2012

A series of 4‐alkylamido‐2‐hydroxybenzoic acids, containing 8–16 carbon atoms in the alkylamido group, has been synthetized and characterized. Surface tension measurements on aqueous solutions have been used to estimate the critical micellar concentrations and the area per molecule at the liquid‐air interface. Light scattering measurements allowed to calculate the aggregation number and the hydrodynamic radius of the micelles.
VUV Flash Photolysis Study of the Reaction of HO with HO2 at 1 atm and 298 K
Authors: Braun M. , Hofzumahaus A. , Stuhl F.
Published: July 2012

Equal concentrations of HO and H were generated by flash photolysing small amounts of H2O diluted in N2 at a pressure of about one atmosphere. Using sensitive detection by resonance absorption, the HO radicals were monitored in the presence and in the absence of O2. In the presence of O2, the radicals were found to disappear significantly faster than in the absence of O2. This enhanced decay is attributed to the fast reaction of HO with HO2. Using simple kinetic arguments and computer modeling, the rate constant, k1, for the title reaction is estimated to be 1.1 · 10−10 cm3 s−1 (+25%; −35%).
Vibrational Energy Flow and Distribution in CF3J and CF3 after Infrared Multiphoton Excitation
Authors: Kauer Matthias , Kleinermanns Carlo
Published: July 2012

Time and wavelength‐resolved infrared emission techniques are used to study the multiphoton excitation and dissociation of CF3J. Fluorescence is detected from the v1‐(sym. CF3‐stretch), v4‐(asym. CF3‐stretch), and v2‐(sym. CF3‐deform.)‐vibrational modes of CF3J and at laserenergies exceeding the dissociation threshold also from CF3 radicals and excited iodine atoms J*(2P1/2 → 2P3/2). – The pumped v1‐ladder of states (v1, v ≧ 1) is populated collision‐free as the fluorescence rise times show. Strikingly different, the v4(v = 1)‐mode is populated via collisions, while the higher v4‐states are populated collision‐free. The v4(v = 1)‐population rate is measured to be (7.1 ± 2). 1013 cm3 mol−1 s−1. – The v1‐ and v4‐emissions show a red‐shift of the band peak and band broadning with increasing laser energy according to higher quanta excitation. – To longer observation times the v1‐ and v4‐bands shift blue again and narrow somewhat according to vibrational relaxation. However at higher laser energies both band peaks do not shift back to their fundamental frequencies, but only decrease in intensity to longer times. This is interpreted as relaxation of these modes by coupling to low frequency modes like the C‐J‐vibrations, which can be easier V‐R, T deactivated. – At laser energies exceeding the dissociation threshold a new emission band is found at 1245 cm−1, due to the C‐F‐stretch of the vibrationally excited CF3‐radical. The rise of the fluorescence signal consists of two parts arising from initially vibrationally hot CF+3 and initially cold CF3, which is subsequently excited by collisions with a rate of (1.7 ± 0.5) · 1013 cm3 mol−1 s−1. – Activation‐ and deactivation rates for various spectral features of the vibrationally excited CF3J molecule and CF3 radical are presented.
Transport Properties of Liquids. IV. Self‐Diffusion, Viscosity, and Density of Irregular Liquid Mixtures: Crown Ether/Alcohol
Authors: Vogel Herbert , Weiss Alarich
Published: July 2012

The dynamic viscosities, the activation energies of the viscous flow Eηa, and the mass densities ϱ were measured for the binary systems 12‐crown‐4/D2O, 12‐crown‐4/ethylene glycol, 12‐crown‐4/methanol, 15‐crown‐5/D2O, 15‐crown‐5/ethylene glycol, and 15‐crown‐5/methanol as a function of temperature T and mole fraction x1 of the crown ether. – Mixtures with bifunctional “alcohols” (D2O, HOCH2CH2OH) showed “broad maxima” in their isotherms η(x1, T = const) and Eηa(x1, T = const), respectively. Correspondingly, the self‐diffusion coefficients D1 of the crown ethers in these mixtures pass a minimum. Quite different is the transport behaviour of the crown ether/methanol system; it behaves with respect to η and D1 almost as ideal system. – The results are discussed by assuming association in the systems, and such a model is also valid for dioxane/H2O and dioxane/ethylene glycol mixtures.
The Temperature Dependence of the Properties of Electrolyte Solutions. IV. Determination of Cationic Transference Numbers in Methanol, Ethanol, Propanol, and Acetonitrile at Various Temperatures
Authors: Barthel J. , Ströder U. , Iberl L. , Hammer H.
Published: July 2012

Cationic transference numbers and conductance data of KSCN and Me4NSCN in methanol (‐15°C to + 25°C), KSCN in ethanol (‐5°C to + 25°C) and propanol (+ 10°C and +25°C), Me4NClO4 and Et4NClO4 in acetonitrile (‐35°C to +25°C) were determined at electrolyte concentrations from 10−3 to 10−2 mol · kg−1. The transference numbers obtained by a moving boundary method were corrected for the changes of the calibration volume resulting from anodic reactions, conductance of the solvent and Joule heating. The data are discussed on the basis of transport equations which take into account short range interactions in the ion distribution functions.
Electrochemical Conversion and Storage of Solar Energy
Authors: Schoonman J.
Published: July 2012

In this study it is shown that the integration of a solid‐state electrode, comprising a proton conducting solid electrolyte and a hydride forming metal, into a photoelectrochemical cell makes solar energy conversion, and in situ storage of hydrogen feasible. The conversion and storage cell is built up of bulk‐, or surface‐doped n‐type SrTiO3 photoanodes, and Zr or Ti cathodes, which are separated from the aqueous electrolyte by the solid proton conductor hydrogen uranyl phosphate tetrahydrate (HUP). The analysis of photocurrent‐voltage characteristics along with the radiation intensity dependence, and of conductivity studies on HUP points to conditions for the improvement of the cell construction. The surface‐ and bulk‐doped SrTiO3 photoanodes employed here will not lead to efficient photoelectrolysis of water due to severe bulk recombination. The influence of electrolyte composition on the photoresponse is discussed. The conversion and storage concept introduced here allows the use of other types of stable photoanodes, and proton conducting solid electrolytes, provided that the solid electrolyte is stable against aqueous electrolytes and metallic hydrides.
Nature of the Electron‐Hole Pair in the System Anthracene Crystal/Rhodamine B Adsorbed from Aqueous Solution Part II: Dependence of Kinetics and Spin‐Dynamics on Shallow Surface Traps
Authors: Papier G. , Charl K.‐P. , Willig F.
Published: July 2012

The dependence of the rhodamine B sensitized hole current (SHC) and of its magnetic field modulation (ΔSHC) on the applied electric field has been measured in anthracene single crystals with different concentrations of shallow surface traps. Our theoretical model for the influence of the magnetic hyperfine effect (HF effect) on the charge carrier kinetics has been extended to account for the effect of shallow traps. The model predicts in agreement with the experimental finding as effect of shallow surface traps, firstly an increase in the magnitude and secondly an increase in the halfwidth of the magnetic field modulation of the SHC, and thirdly a weakened influence of the electric field on these two signals. The smallest concentration of shallow surface traps was found on naturally grown surfaces of sublimation crystals, whereas solution grown crystals showed in general a higher concentration of such traps. It was found that shallow hole traps can be induced with carbazol molecules.
Influence of Titanium Suboxides on the Photoelectrochemical Efficiency of Oxidized Titanium Electrodes
Authors: Antonucci V. , Miceli P. , Giordano N. , Bart J. C. J.
Published: July 2012

Pure titanium laminae were oxidized in CO2 atmosphere between 300°C and 700°C and used as electrodes in the photodecomposition of water. X‐ray diffraction and the method of interference indicators have been exploited to characterize the initial stages of the oxidation of titanium. Metallic interstitial suboxides TiO0+x are essentially photoinactive but promote the efficiency of an overlaying non‐stoichiometric rutile scale.
Ansätze zur Beurteilung des isothermen Umsatzverhaltens von “Supported Liquid‐Phase Catalysts”
Authors: Hesse D.
Published: July 2012

The investigation of isothermal conversion behavior of supported liquid‐phase catalysts has shown that the reaction rate as a function of liquid loading always reaches a maximum value, if the pore volume of the porous solid is filled between 40% and 60% with the catalyst solution. In order to interpret this particularity, a so‐called ideal SLP catalyst in which the pore space cannot be blocked by the impregnation process is discussed first. The results obtained lead to the conclusion that the conversion behavior of real SLP catalysts is mainly influenced by the blocking process. Its effect upon the reaction rate can be described by means of a parameter which values depend on the extent to which the permeability of the support changes with liquid loading. This function can be determined by measuring the overall effective gas diffusivity in the porous material loaded with the pure solvent.
Matrix Isolation Studies on Some Molecular Oxo‐anion Salt Vapours
Authors: Ogden J. S.
Published: July 2012

In this presentation examples are discussed to illustrate how matrix isolation may be used in the characterisation of high temperature molecules. It is evident that in addition to the stabilisation afforded by trapping in an inert environment at low temperatures, an important feature is the ability to obtain well‐resolved vibrational isotope data. For small, light molecules, this information can lead to estimates of bond angles, whilst for more complex species, the observation of characteristic isotope patterns produces a valuable indication of molecular shape.
Magic Numbers in Mass Spectra of Xe, C2F4Cl2 and SF6 Clusters
Authors: Echt O. , Reyes Flotte A. , Knapp M. , Sattler K. , Recknagel E.
Published: July 2012

Mass spectra of xenon clusters show pronounced intensity maxima for cluster sizes n* = 13, 19, 25, 55, 71, 87, and 147. The occurrence of these “magic numbers” is explained by shell closure of clusters growing in the icosahedral structure. Magic numbers in mass spectra of 1,2‐dichlorotetra‐fluoroethane are n* = 13 and 19. The only intensity maximum of sulfurhexafluoride clusters occurs at n* = 13, whereas a minimum is observed at n* = 18. In contrast, the size distributions of clusters of 17 other molecular gases decrease strictly monotonically with increasing size. The origin of these effects is discussed.
Thermodynamics and Electrochemistry of Simple Ions in Ammonia
Authors: Schindewolf U.
Published: July 2012

A compilation of the thermodynamics of simple ions in ammonia is given, based on thermodynamic data of their salts, on some electrochemical data and on those of solvated electrons. The final data are expressed in terms of the solvation enthalpies, solvation entropies and electrode potentials of the ions. With the uncertainties of the work function of the metals and that of the surface potential of the solvent, the concept that solvated electrons are partner of any redox equilibria allows the calculation of the “absolute” electrode equilibrium potential of any electrode in contact with the solution of any redox pair. This is exemplified for a cesium and a silver electrode in ammonia. ‐ Finally the differences in the kinetics of solvated electrons in water and in ammonia with respect to the reaction with the solvent are expressed qualitatively by the transition state theory making use of the thermodynamic data of the solvated electrons. The high stability of electrons in ammonia is due to their very high positive partial molar entropy.
Energetics and Stabilities of the IIB/VIA‐Compounds at High‐Temperature Equilibrium Conditions
Authors: Grade M. , Hirschwald W.
Published: July 2012

Equilibrium vaporization behaviour of twelve IIB/VIA‐compounds of the type MeX was studied by means of high‐temperature mass spectrometry. In all cases except HgTe the existence of stable MeX(g)‐molecules was established. Bond energies D0(MeXgas) were determined by the thermodynamic third‐law method and range as follows: ZnO(g) (280.1 kJ/mol)/ZnS(g) (224.8)/ZnSe(g) (170.8)/ZnTe(g) (117.7)/CdO(g) (230.3)/CdS(g) (208.5)/CdSe(g) (127.7)/CdTe(g) (100.1)/HgO(g) (221.1)/HgS(g) (217.3)/HgSe(g) (144.5). ‐ Comparison of the third‐law bond energies with existing experimental data, upper limits of D0 given by other authors, and semi‐empirical estimates shows basic agreement. Data for the heat of dissociative vaporization ΔH0R, the heat of atomization ΔH0at, the parameter magnified image, and the chemical stabilities of the IIB/VIA‐systems are also presented.
Photoelectrochemical Studies of Electrodes Coated with Merocyanine Dye
Authors: Mizutani Fumio , Iijima Sei‐Ichiro , Sasaki Kanji , Shimura Yukio
Published: July 2012

Deposited films of merocyanine dye (3‐carboxymethyl‐5‐[2‐(3‐octadecyl‐2‐benzothiazolinylidene)ethylidene]‐2‐thioxo‐4‐thiazolidinone) show various kinds of intra‐ and intermolecular changes when they are heated and/or soaked in a neutral aqueous solution. The effect of such changes on photocurrent has been examined using electrodes coated with the dye film. A remarkable high quantum efficiency (above 10%) for cathodic photocurrent has been obtained when the dye film shows red‐shifted absorption bands owing to the dye aggregation. The high photoactivity is attributable to the high transfering ability of excitons in the aggregates.
Role of Solvation and Desolvation in Polymer “Catalysis” [1]. VI. Influence of Ionic Valencies of Reactants on the Desolvation Effects in the Spontaneous and Hg2+‐Induced Aquation of Co(NH3)5SO4+, Co(NH3)5Br2+ and Cr(NH3)5Br2+ [2]
Authors: Okubo Tsuneo , Yamamura Yoshio , Ise Norio
Published: July 2012

Spontaneous and Hg2+‐induced aquation reactions of Co(NH3)5SO4+ are studied in the presence of sodium polyethylenesulfonate and sodium polystyrenesulfonate under high pressure. The spontaneous aquation rates are in the order of Co(NH3)5SO4+, Co(NH3)5Br2+ and Cr(NH3)5Br2+ and is accounted for in terms of the Brönsted‐Bjerrum theory. The volume of activation (ΔV#) of both spontaneous and Hg2+‐induced aquations of Co(NH3)5SO4+ greatly increased by addition of the macroions, which is attributed to stronger desolvation of the activated complex than the reactant in the strong electrostatic field of the macroions.
The Thermal Conductivity of Mixtures of Methane with Carbon Dioxide
Authors: Kestin J. , Ro S. T. , Nagasaka Y.
Published: July 2012

The paper is an addendum to two previous papers which contained data on the thermal conductivity of the systems H2‐ N2and N2‐ CH4. The present system is CH4‐ CO2, thus forming a natural progression in the complexity of the molecular structure of the set of binary systems under investigation. The system chosen for study is still characterized by nearly spherical intermolecular force potentials. — The results extrapolated to zero density show excellent agreement with the Monchick‐Pereira‐Mason theory and continue to demonstrate that the inelastic‐collision term is small (∼ 1%), thus asserting that the Hirschfelder‐Eucken approximation is acceptable. — At higher densities, the version of the Thorne‐Enskog theory due to Mason et al. gives a systematic deviation of only — 2% over the whole composition range.