bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman Spectra of Water to 400°C and 3000 bar
Authors: Kohl W. , Lindner H. A. , Franck E. U. 
Published: July 2012

AbstractA small‐size high‐temperature, high‐pressure Raman cell of about 1.6 cm3 internal volume with four sapphire windows is described. It can be used to 400°C and 3000 bar. The OD‐stretching bands around 2600 cm−1 of HDO diluted in H2O have been measured from 25°C to 400°C and in a density range between 0.04 g·cm−3 to 1.0 g·Cm−3. The critical temperature of water Tc is 374°C, the critical density ϱC = 0.32 g°cm−3. At the supercritical temperature of 400°C the OD‐band was determined at densities from 0.04 to 0.8 g·cm−3. At nearly constant densities between 1.0 and 0.8 g·cm−3 the band was recorded from 25 to 400°C. Thus the OD‐band, which depends on hydrogen bonding, could be studied in a wide range of temperatures and pressures, avoiding the immediate critical region.—At 400°C and low density the sharp narrow OD‐band has a maximum frequency of 2727 cm−1. It becomes broader and shifts to 2668 cm−1 at 0.8 g·cm−3. A very broad band occurs at 25°C and 1 g·cm−3 at 2530 cm−1. Depolarization ratios were measured, local field corrections were applied and permitted the determination of isotropic and anisotropic spectra. The transition of band shape in the wide range of temperature and density is always smooth with no prominent features. As compared with a two‐component hydrogen‐bonded and non‐bonded “mixture” model a description with a “continuum”‐model as proposed by Efimov et al. appears to be preferable. Specific interaction energies have been derived from this description.
Imidazole‐Catalyzed Hydrolysis of Substituted Benzoate Esters. A Detailed Kinetic and Mechanistic Study
Authors: Menegheli Paulo , Farah João P. S. , Seoud Omar A. El 
Published: July 2012

AbstractKinetic and mechanistic details of the imidazole‐catalyzed hydrolysis of substituted phenyl benzoates in 10% acetonitrile in water (V/V) were examined. The following 4 ester series were studied: p‐nitrophenyl p‐X‐benzoates (X = CH3, H, Cl, CN, NO2, series I), p‐Y‐phenyl p‐nitrobenzoates (Y = CH3, H, Cl, CN, NO2, series II), 2, 4‐dinitrophenyl p‐X‐benzoates (X = CH3O, H, Cl, CN, NO2, series III) and p‐Y‐phenyl 2,4‐dinitrobenzoates (Y = CH3, H, Cl, CN, NO2, series IV). Based on: catalytic rate constants, activation parameters, kinetic solvent isotope effects, Hammett (δ) values and the spectroscopic detection of the reaction intermediates, the following conclusions were reached: a) imidazole acts as a nucleophilic catalyst, i.e., the hydrolysis occurs via the intermediate formation of acylimidazole; b) the leaving group is the phenoxide ion; c) the rate limiting step is the decomposition of the tetrahedral intermediate that precedes the acylimidazole (series I, II and IV) or the attack of imidazole on the acyl group of the ester (series III).
The Dimerization Energies of the Ge2S2, Ge2Se2, and Ge2Te2 Molecules
Authors: Balducci G. , Sacconi L. Vitalini , Gigli G. 
Published: July 2012

AbstractThe germanium monochalcogenide molecules Ge2S2, Ge2Se2, and Ge2Te2 were identified in a Knudsen cell mass spectrometric study of the vapors in equilibrium over solid GeS, GeSe, and GeTe. From a second and third law evaluation of the equilibrium data the following dimerization energies ΔH0,dimo were determined: 106.5 ± 2.1, 102.1 ± 4.6, 102 ± 8 kJ mol−1 for Ge2S2, Ge2Se2, Ge2Te2, respectively. These data and literature data allow to look into trends of the bonding energetics of group IVB‐VIB gaseous compounds.
Two‐Dimensional Phase Transitions and Correlation Field Splitting in Unimolecular Layers of CO Physisorbed on NaCI(100) as Detected by Polarization Fourier‐Transform IR Spectroscopy
Authors: Heidberg J. , Suhren M. , Weiss H. 
Published: July 2012

AbstractA phase transition in the monolayer CO physisorbed on NaCI(100) was observed by means of polarization Fourier‐transform infrared spectroscopy. Above 35 K the spectra are in concert with molecules oriented perpendicularly to the surface, the unit cell being of p(1 × 1) symmetry. Below 35 K the molecules tilt, and a correlation field splitting appears. In this temperature range the spectra are in accordance with a p(2 × 1) structure with two equivalent molecules per unit cell, which are connected by a glide plane. Submonolayer spectra indicate random distribution of perpendicularly oriented CO molecules above 35 K, while at temperatures below 35 K ordered islands are formed.
Adsorption and Reaction of Butenes on Polycrystalline Nickel Films
Authors: Klingenberg B. , Haseneder R. , Borgmann D. , Wedler G. 
Published: July 2012

AbstractSupplementary to literature on spectroscopic investigations of butenes adsorbed on transition metal surfaces at 273 K, the gas phase which is in equilibrium with the adsorbed layer has been analysed. Isothermic reaction mass spectrometry (IRMS) and thermal desorption spectroscopy (TDS) were applied. It is shown that for cis‐2‐butene, trans‐2‐butene, 1‐butene and 2‐methyl‐propene (iso‐butene) considerable hydrogen abstraction and partly C–C‐bond cleavage takes place. In the monolayer range methane appears in the gas phase. At coverages exceeding a monolayer hydrogen, butane and butene become the main components. Thermal desorption spectroscopy after adsorption at 77 K shows only hydrogen and methane at rather high temperatures. Starting with a multilayer adsorption of butenes at 77 K leads to desorption of butene, butane, hydrogen and methane.
Adsorption and Reaction on Oxide Surfaces: CO and CO2 on Cr2O3(111)
Authors: Kuhlenbeck H. , Xu C. , Dillmann B. , Haßel M. , Adam B. , Ehrlich D. , Wohlrab S. , Freund H.‐J. , Ditzinger U. A. , Neddermeyer H. , Neumann M. , Neuber M. 
Published: July 2012

AbstractWe have investigated the adsorption of CO and CO2 on epitaxially grown Cr2O3(111) by means of EELS. LEED, ARUPS, NEXAFS and XPS. CO is found to adsorb on the oxide surface in an ordered (√3 × √3)R30° structure with the molecular axis oriented approximately parallel to the surface. CO2 on the other hand reacts with the chromium oxide to form a surface carbonate. Adsorption of CO, respectively reaction of CO2 only takes place on a clean, freshly flashed oxide surface. Preadsorption of oxygen leads to a surface which is rather inert to adsorption, likely due to electronic or steric reasons.
Volume‐Gravimetric Measurements of Binary Gas Adsorption Equilibria
Authors: Keller J. U. , Staudt R. , Tomalla M. 
Published: July 2012

AbstractAdsorption equilibria of binary gas mixtures on rigid solid adsorbents like activated carbons (AC) and molecular sieves (MS) can be measured “on line” by combining the (well known) gravimetric and the volumetric method. The resulting volume‐gravimetric method is described. Also the basic equations necessary to calculate the masses of each of the two adsorbed components are formulated. Explicit solutions for binary ideal gas adsorptives are given. The experimental device used for measurement is outlined. Data for coadsorption equilibria of a N2/CH4 mixture on activated carbon AK WS IV‐G 20575 at T = 298 K in the pressure range 1–20 bar are reported and discussed to a certain extend.
35Cl Nuclear Quadrupole Resonance and X‐Ray Studies on Mono‐, Di‐, and Trichloroacetates of Dimethylanilines
Authors: Basaran Reha , Dou Shi‐Qi , Weiss Alarich 
Published: July 2012

AbstractThe 35Cl NQR spectra of 15 mono‐, di‐, and trichloroacetates of dimethylanilines [2,3‐, 2,4‐, 2,5‐, 2,6‐, 3,5‐(CH3)2C6H3NH3⊕] [Cl3‐nHn CCOO⊖],n = 0,1,2, have been studied in the range 77 ≤ T/K ≤ Tb (Tbleaching out). – 35Cl NQR signals are observable for trichloroacetates of dimethylanilines in the range 77 ≤ T/K ≤ 200, dichloroacetates of dimethylanilines in the range 77 ≤ T/K ≤ Tdecomposition, and for monochloroacetates of dimethylanilines in the range 77 ≤ T/K ≤ room temperature. – The crystal structures of [2,3‐(CH3)2C6H3NH3⊕] [Cl2HCCOO⊖] and of [2,4‐(CH3)2C6H3NH3⊕] [Cl3‐nHnCCOO⊖], n = 1,2, were determined at room temperature. Crystal structures and 35Cl NQR spectra are compared and discussed.
Photoelectrochemical Investigations on Al and In Co‐doped ZnS Thin Film Electrodes in an Aqueous Electrolyte
Authors: Döring H. , Hashimoto K. , Fujishima A. 
Published: July 2012

AbstractAl doped and Al‐In co‐doped ZnS thin film electrodes were grown by electron‐beam evaporation on ITO (indium‐tin oxide) glass substrate, and their photoelectrochemical properties were investigated. These thin films were also characterized by optical absorption, X‐ray diffraction (XRD) and X‐ray photoelectron spectrum (XPS) measurements. The doping of the ZnS film with Al alone did not result in a satisfactory n‐type semiconductor. For Al‐In co‐doped ZnS thin films prepared by the thermal diffusion of a thin In layer which was deposited previously on the ITO‐glass substrate, however, the barrier resistance between ITO and ZnS was lowered, and a clear n‐type semiconductor characteristic was observed. The efficiencies of both the photocurrent and photocorrosion of ZnS in an aqueous electrolyte were increased with higher Al concentration.
The Photochemistry of α‐Phenoxyacetophenones Investigated by Flash‐CIDNP‐spectroscopy
Authors: Palm W.‐U. , Dreeskamp H. , Bouas‐Laurent H. , Castellan A. 
Published: July 2012

AbstractThe photochemistry of 14 different substituted α‐phenoxyacetophenones (1) was studied by CIDNP‐spectroscopy using an XeCl excimer laser (308 nm) and a 250 MHz 1H‐NMR spectrometer. To characterize the excited states the electronic absorption and emission spectra as well as disappearance quantum yields were investigated also. – Two reaction channels were established: 1) β‐cleavage from the singlet state; and 2) the formation of acetophenones via the respective enol forms where the origin of the polarization remains unclear. It is concluded that these are the main reaction channels, since all products formed show polarizations in the CIDNP‐spectra. – In contrast to the current assumptions for the typical acetophenone reaction of (1) leading to the β‐cleavage, we are led to interprete the CIDNP‐spectra of (1) as a result of a reaction due to the phenoxy part with all characteristics of a photo‐Claisen reaction.
Structural Properties of Mixed Langmuir‐Blodgett Films of 11‐(9‐Carbazolyl)undecanoic Acid and Palmitic Acid Deposited from Compressed Monolayers
Authors: Nagamura Toshihiko , Kamata Shigenobu , Ogawa Teiichiro 
Published: July 2012

AbstractThe surface pressure‐molecular area isotherms for various mixtures of 11‐(9‐carbazolyl)undecanoic acid (CUA) and palmitic acid (PA) showed plateau at about 13 mN · m−1 at 15°C. The width of plateau increased with the molar fraction of CUA. A bilayer structure due to the squeezing‐out of CUA from mixed monolayers at the air/water interface was suggested from π‐A isotherms and the limiting area. The structure of Langmuir‐Blodgett (LB) films of a 1:2.7 mixture of CUA and PA deposited at 15°C and 20 mN · m−1 by a vertical dipping method was studied by the small‐angle X‐ray scattering, absorption, and capacitance measurements These results showed that LB films deposited at 20 mN · m−1 were usual Y‐type composed of a monolayer unit. It was strongly suggested that CUA partially squeezed‐out at the air/water interface was reorganized to mixed monolayers during a transfer process.
Electroreduction of Substituted Naphthylhydrazones in DMSO
Authors: Vasudevan D. , Venkatachalam C. S. , Kalidas C. 
Published: July 2012

AbstractStudies on the electroreduction of 4‐chloro‐1‐naphthylhydrazonodimedone (4‐Cl‐1‐NHD), 4‐sulpho‐1‐naphthylhydrazonodimedone (1‐NHD‐4‐SO3H) and 2‐hydroxy‐4‐sulpho‐1‐naphthylhydrazonodimedone (2‐OH‐1‐NHD‐4‐SO3H) have been carried out in 0.1 M TEAI‐DMSO using various electrochemical techniques. Each depolariser exhibits three polarographic dc waves, ac peaks or CV peaks, respectively, the nature of which have been discussed. Further, from the results of microcoulometry and macroscale cpe. a complex mechanism has been suggested for the electroreduction of these hydrazones. The mechanism has been supported by in‐situ EPR measurements, evaluations of the charge‐transfer rate constants and chromatographic analysis (by TLC and HPLC) on the products of macroscale cpe.
Heat of Dilution in Aqueous and Methanolic Formaldehyde Solutions
Authors: Hasse Hans , Maurer Gerd 
Published: July 2012

AbstractAs part of an ongoing project dealing with thermodynamic properties of formaldehyde containing fluid mixtures, heats of dilution of formaldehyde, water, methanol and trioxane containing mixtures have been measured in a heat flow calorimeter at temperatures between 298 and 363 K. New mixing cells, allowing pressurization and avoiding vapor‐space, were used to take over 300 data points covering binary, ternary and quarternary mixtures. The observed heats of dilution are generally small (less than 250 J/mol). They are correlated using a physico‐chemical model. Physical effects are considered by the UNIFAC‐group contribution method, reaction enthalpies are used for the description of the chemical contributions. The model allows a good representation of most of the binary data, extrapolations to multicomponent systems using binary data alone are, however, only qualitatively correct.
Power‐Law Behavior in the Frequency dependence of the Electrical Conductivity of Poly(L‐Glutamic Acid) Aqueous Solutions
Authors: Bordi F. , Cametti C. , Paradossi G. 
Published: July 2012

AbstractThe electrical conductivity of poly(L‐glutamic acid) in aqueous solutions was measured in the frequency range from 0.5 MHz to 100 MHz, following the entire helix‐coil transition induced by change of pH. The frequency behavior of the conductivity can be described by a power law whose exponent varies from 2 at low degree of ionization (full‐helix conformation) to about 1 at higher degrees of ionization (full‐coil conformation). A possible mechanism involving the motion of polar side chains is proposed.
A Molecular Dynamics and X‐ray Diffraction Study of MgCl2 in Methanol
Authors: Tamura Y. , Spohr E. , Heinziger K. , Pálinkás G. , Bakó I. 
Published: July 2012

AbstractA recently developed flexible three‐site model for methanol was employed to perform a Molecular Dynamics simulation of a 0.6 molal MgCl2 solution. The ion‐methanol and ion‐ion potential functions were derived from ab initio calculations. The structural properties of the solution are discussed on the basis of radial and angular distribution functions, the orientation of the methanol molecules, and their geometrical arrangement in the solvation shells of the ions. The dynamical properties of the solution are calculated from various autocorrelation functions. Results are presented for the influence of the individual ions on self‐diffusion coefficients, hindered translations, and internal vibrations of the methanol molecules. The comparison of calculated X‐ray structure and pair correlation functions with those got from a newly performed X‐ray measurement on the same solution shows good agreement.
Calculation of High Pressure Phase Equilibria of Mixtures of Ethylene, Vinylacetate and an (Ethylene‐Vinylacetate) Copolymer
Authors: Finck Udo , Wohlfarth Christian , Heuer Tilo 
Published: July 2012

AbstractSome new measurements of the high pressure demixing behaviour have been done in the system ethylene, vinyl acetate and an (ethylene‐vinylacetate) copolymer. Calculations of phase equilibria using the chain‐of‐rotators equation of state are compared with these new experimental data The miscibility gap of the ternary mixture can be predicted on the basis of a group contribution approach using interaction parameters from low molecular weight binary mixtures only. The model describe the phase separation (besides of polydispersity effects) sufficiently accurate up to high pressures. The derivation of the spinodal equation for ternary mixtures facilitates the calculation procedures applied. The model calculations detect a closed miscibility gap at higher pressures than in the binary subsystem composed of ethylene and the (ethylenevinylacetate) copolymer. Experimental evidence for this behaviour is open, however.
Solvent Induced Broadening of Fluorescent Electronic Transitions of Paraterphenyl
Authors: Sander R. , Menzel R. , Naumann K.‐H. 
Published: July 2012

AbstractWe investigate the solvent influence to the inhomogeneous broadening of the fluorescent electronic transitions of paraterphenyl. The broadening is described in a phenomenological way by modeling the measured spectra with a sum of Gaussian functions. Lorentzian functions are also tested. Although the solvent properties are varied considerably the halfwidth of these subbands only changes about ± 12%. Molecular dynamic calculations predicted an influence of geometric solvent parameters like packing density and solvent diameter to the inhomogenous broadening. A method for the calculation of these parameters from thermodynamic properties of the solvents is presented. The halfwidths of the fitted subbands are discussed as functions of several solvent parameters (e.g. dielectric constant, geometric solvent parameters). By normalizing the halfwidths to a constant packing density of solvent molecules the correlations can be improved. It becomes evident, that geometric solvent properties do have at least a similar effect to inhomogeneous broadening of the measured electronic transitions than other solvent parameters.
A STM Investigation of Pt‐Single Crystal Surfaces in Air and Electrolyte Solutions
Authors: Vogel R. , Kamphausen I. , Baltruschat H. 
Published: July 2012

AbstractWe describe the construction of a beetle‐type scanning tunneling microscope optimized for in situ measurements. The influence of the crystal preparation technique on the surface structure is reported. Whereas annealing of platinum single crystals in iodine vapour yields smooth surfaces for the low index faces, which are protected from contamination in air by the adsorbed iodine, facetting occurs in the case of stepped surfaces. — The iodine adlattices are resolved both in air and electrolyte: Pt(111) (3 × 3)‐I and Pt(100) (√2 × 5√2)R45°I, thus confirming previous LEED results.
Electric Double Layer at the Membrane/Solution Interface: Distribution of Electric Potential and Estimation of the Charge Stored
Authors: Manzanares J. A. , Mafé S. , Bisquert J. 
Published: July 2012

AbstractThe classical equations for the equilibrium electric double layer (EDL) at the charged membrane/solution interface have been solved and distributions of the electric potential and estimations of the charge stored are presented for some typical situations. The theoretical treatment is based on the full, non‐linearized Poisson‐Boltzmann equation, and includes partition coefficients and an adsorption isotherm for the concentration‐dependent fixed charge in a membrane immersed in a ternary electrolyte system. The physical trends observed for the Donnan and surface potentials and for the charge stored when the characteristics parameters of the EDL are varied have been discussed. Finally, the results obtained with the depleted layer model with concentration‐dependent fixed charge are compared to those resulting from the diffuse double layer model.
Kinetics of the Dehydration of the β‐Cages of Sodium Faujasites as Studied by H‐NMR Spectroscopy
Authors: Basler W. D. , Lechert H. T. , Carboo D. , Knöchel A. 
Published: July 2012

AbstractThe kinetics of the dehydration of the β‐cages of sodium faujasites have been studied by NMR methods. For Na — Y type (Si/Al > 2) the rate of passing from the β‐cages into the supercages is slow and only weakly dependent on temperature (activation energy EA = 4.1 kJ/mol). This is in contrast to the strongly temperature dependent (Ea = 100 kJ/mol) rate of penetration from the supercages into the β‐cages. A model is proposed assuming the formation of a water‐ion complex. The slow rate is explained by a negative complex formation entropy (−40R) due to spatial constraints in the β‐cages. The activation energy is small because the enthalpy of the penetration is nearly canceled by the negative complex formation enthalpy.
Thermodynamic Activation Parameters for Viscous Flow in Acetonitrile‐Water‐Electrolyte Systems
Authors: Kumar Gopu 
Published: July 2012

AbstractFeakins‐Lawrence extension of Eyring's transition state theory for viscosity of electrolyte solutions has been applied to aqueous acetonitrile solutions of potassium halides and tetraalkylammonium bromides at 5, 15, 25 and 35°C. The molar contributions of the electrolytes namely free energy (Δμ3o*), enthalpy (ΔH3o*) and entropy (ΔS3o*) to the activation parameters for viscous flow of the ternary system were evaluated using viscosity data. The results are discussed in terms of ion solvent bond‐making, bond‐breaking and in the light of the recently proposed new theory of Feakins.
Contact‐Complex Formation Reaction between Solvent Molecules in Square‐Well Fluids 1. One‐Dimensional Fluid
Authors: Yoshimura Y. 
Published: July 2012

AbstractContact‐complex formation reaction between solvent molecules in square‐well fluids has been studied for the one‐dimensional system. The packing effect due to the hard repulsive interaction stabilizes the contact complex, while the effect of the attractive interaction always restrains the contact‐complex formation in one‐dimensional fluids. The density dependence of the equilibrium constant shows an interesting behavior due to the trade‐off between these two factors. When the attractive interaction is sufficiently large, the equilibrium constant may decrease with increasing density. On the other hand, the equilibrium constant of the contact‐complex formation converges to that in the hard rod fluid at the high density limit. The results qualitatively agree with the findings for the solvent effects on the electron‐donor‐acceptor‐complex formation reaction.
Photoisomerization Dynamics of 3,3′‐Diethyl Oxacarbocyanine. Intramolecular and Solvent Viscosity Effects
Authors: Ponterini Glauco , Caselli Monica 
Published: July 2012

AbstractThe dynamics of photoisomerization and of ground‐state back isomerization of 3,3′‐diethyl oxacarbocyanine (DOC) in linear alcohols are analyzed. “Intramolecular” activation energies are obtained and compared with those of the corresponding dicarbocyanine (DODCI) in an attempt at establishing the consequence of the polymethine chain lengthening on the isomerization dynamics. The activation energy for the photoisomerization of DOC is slightly lower than that of DODCl, whereas the reverse is found for the ground‐state back isomerization. The coupling of the internal twisting coordinate with solvent drag is analyzed within the framework of the hydrodynamic Kramers model. Although this approach does not provide a fully satisfactory description of the experimental points, it has been taken as a reference model: the parameters obtained from the data fitting have been assigned a semi‐quantitative significance and a number of possible reasons of breakdown of the hydrodynamic Kramers description have been considered and qualitatively discussed.
CARS Measurements and Numerical Simulation Results for Methane/Air Counterflow Flames
Authors: Dießel E. , Dreier T. , Lange B. , Wolfrum J. , Behrendt F. , Warnatz J. 
Published: July 2012

AbstractIn extension of previous work a comparison has been made between experiments and numerical simulation results across the flame front of an atmospheric pressure methane/air counterflow diffusion stabilized in the forward stagnation region of a cylindrical porous burner plate. Temperature profiles have been measured by CARS spectroscopy on molecular nitrogen. The experimental data are compared with results of numerical calculations using a computer code based on a one‐dimensional boundary layer approximation. This work covers pure diffusion flames at different strain rates as well as partially premixed flames at two stoichiometries and strain rates. The results indicate good agreement between measured and calculated temperature profiles with regard to peak temperature location of the flame front, temperature gradients and overall shape of the non‐premixed and partially premixed flames, respectively.