bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectroscopy and Photodissociation Dynamics of Highly Vibrationally Excited Molecules
Authors: Likar M. D. , Sinha A. , Ticich T. M. , Vander Wal R. L. , Crim F. F. 
Published: March 2014

AbstractVibrationally mediated photodissociation is a technique for studying the spectroscopy and photodissociation dynamics of highly vibrationally excited molecules. One photon prepares a highly vibrationally excited molecule by excitation of a vibrational overtone transition, and a second photon of the same or different wavelength fragments the molecule by excitation to a dissociative electronic state. A third photon from a probe laser interrogates individual quantum states of the fragment by laser induced fluorescence. Applying this technique to hydrogen peroxide and nitric acid provides vibrational overtone excitation spectra in the regions of the 4υOH and 5υOH transitions in HOOH and in the region of the 4υOH transition in HONO2. The photodissociation dynamics arc modified by the participation of the highly vibrationally excited intermediate state. In both HOOH and HONO2, the OH fragment is created with more vibrational energy than in the one‐photon ultraviolet photolysis. In the dissociation of HONO2, a large fraction of the available energy appears in internal excitation of the NO2 fragment, possibly including electronic excitation.
Absorption Spectrum versus Excitation Spectrum of Pyrazine
Authors: Drabe Karel E. , Kommandeur Jan , van Herpen Willy M. , Meerts Leo W. 
Published: March 2014

AbstractThe first ME spectrum of pyrazine was measured as an excitation spectrum. Assuming the quantum yield to be constant over the spectrum it was considered as an absorption spectrum and de‐diagonalisation led to zero order energies and coupling constants of the singlet and triplet states. – By measuring the lifetimes of eight strong ME's we have now shown that the quantum yield varies by as much as a factor of three over the spectrum. With these lifetimes the excitation spectrum can be converted into a real absorption spectrum and a new and now correct set of values for the zero order energies, their widths and the coupling constants was obtained. The most important result is the fact that the zero order singlet and triplets decay non‐radiatively at different rates.
Can High‐Resolution Molecular Spectroscopy Help to Understand Intramolecular Energy Transfers?
Authors: Graner Georges 
Published: March 2014

AbstractAfter a short discussion of the exact meaning of intramolecular processes, a description is given of interactions and perturbations as they are revealed through high resolution molecular spectroscopy. The case of the 3 μm fluorescence of CH3F will be used to illustrate possible pathways for energy flows.
Intramolecular Conversions Over Low Barriers IX: Vibrational Bottle‐Necks at Statistical Equilibrium
Authors: Bauer S. H. , Borchardt D. B. , Chiu N.‐S. 
Published: March 2014

AbstractThe presence of bottle‐necks in IVR rates is indicated by the inverse dependence of a group of bimolecular rate constants on density, at low densities. The previously proposed model for relaxation times of systems in dynamic equilibrium (typical of isomerizations over low barriers) can be extended to make transparent the role of individual vibrational states. A coupling parameter can be explicitly introduced (for each molecular species) which relates the probability for intramolecular energy transfers to the amounts of energy which have to be converted from the non‐involved oscillators to the one (υα) which comprises the reaction coordinate (ζ). The essential function is f(q; E), which is the number of states within the interval E and (E + ΔE) [for a total state density g(E)] which incorporate excitation of any particular v, state. The total energy space is divided into a large number of “bands” between which both collisional and collisionless energy transfers take place. The relaxation time is obtained from the lowest non‐zero root of a large secular determinant.
Eigenstate‐resolved Vibrational State Mixing in Jet‐Cooled 1‐Butyne Near 3333 cm−1
Authors: De Souza A. M. , Kaur Devinder , Perry David S. 
Published: March 2014

AbstractIn the high resolution infrared spectrum of the acetylenic C —H stretch of 1‐butyne, considerable vibrational state mixing is observed. The multiplets of sharp features observed under cooled jet conditions (3 K) are attributed to vibrational state mixing. A dependence of the intramolecular vibrational redistribution (IVR) on the rotational quantum numbers, J and Ka, is found.
Rates of Intramolecular Singlet‐Singlet and Triplet‐Triplet Energy Transfer within One Molecule, an Anti‐Syn‐Bis‐Bimane
Authors: Kosower Edward M. , Giniger Rina 
Published: March 2014

AbstractThe rate constants for intramolecular singlet‐singlet (anti → syn) and triplet‐triplet (also anti → syn) energy transfer in a bis‐bimane, a syn‐anti‐bis‐bimane, in which a dimethylene bridge connects the photophysically active moieties, have been estimated on the basis of radiative rate constants and quantum yields of fluorescence and phosphorescence of syn‐(1) and anti‐(2) bimanes and rate constants of intersystem crossing and photochemical reaction in an anti‐bimane.
An Investigation of Electron Transfer Reactions between Aromatic and Quinoid Systems
Authors: Goez M. , Jaenicke W. , Nickel U. 
Published: March 2014

AbstractA classical organic redox reaction is the conversion of an aromatic compound from its reduced form R to a semioxidized state S, and further to a totally oxidized (quinoid) species T. Complex redox systems are present in a reaction of quinoid and aromatic forms derived from different parent compounds. In this case, the exchange of one or two electrons in one step between T and R can be distinguished experimentally. These reactions were investigated in a stopped‐flow apparatus with optical detection. In the system N,N,N′,N′‐tetramethyl‐para‐phenylene‐diamine/N,N‐dimethyl‐para‐phenylene‐diamine the rate constants for all elementary reactions have been determined. Protonated, and unprotonated R were found to be reactive. In this system, as well as the others considered, no direct transfer of two electrons between T1and R2takes place. The essential steps of the mechanism have to be seen in a mixed symproportionation yielding S1and S2, and a subsequent fast oxidation of S2by surplus starting material T1. As a generalization, a tangent criterion has been derived to distinguish between one‐ and two‐electron steps in such mixed redox systems.
A Proton Magnetic Resonance and Gravimetric Study of Water and Isopropanol Adsorption on Microcrystalline Rutile. I. Adsorption Sites
Authors: Boddenberg B. , Horstmann W. 
Published: March 2014

AbstractThe adsorption of water and isopropanol on a pure microcrystalline rutile has been studied by means of conventional adsorption isotherm and 1H magnetic resonance intensity measurements. Evidence is obtained that irreversible adsorption of both water and isopropanol is caused by bonding to the coordinatively unsaturated Ti4+ ions of the (110) crystallographic planes which contribute by about 85% to the surface area exposed. On these planes water is displaced by isopropanol such that the amount of alcohol adsorbed is not influenced by preadsorbed water. Reversible isopropanol adsorption is attributed to bonding onto Ti4+ sites of the remaining planes exposed, most likely (100) and (101). It is suggested that isopropanol adsorption can be used to determine the specific surface area of microcrystalline rutile as well as the fraction of it which consists of the (110) crystallographic planes.
Coherence in Disordered Condensed Matter. I: Dissipative Structures in Liquids and Dynamics of Far‐Infrared Absorption
Authors: Chatzidimitriou‐Dreismann C. A. , Brändas E. J. 
Published: March 2014

AbstractThe Complex Scaling Method (CSM), in connection with Prigogine's Subdynamics predicts the spontaneous emergence of large dissipative (or: coherent) structures in amorphous matter, like liquids. The connection between these structures and the appearance of a large Jordan block (see appendix) with Segré characteristic equal to the dimension or degrees of freedom of the emerged structure, in the CSM‐transformed reduced second order density matrix, is presented and analysed in some detail. The interdependence of the present theoretical considerations with Yang's concept of off‐diagonal long‐range order (ODLRO) is stressed. – The appearance of dissipative structures is accompanied by a quantization condition for the lifetimes of the states contributing to the creation of those structures. The minimum size nmin of a dissipative structure obeys the equation nmin ≅ τrot · (2πkBT/h), where τrot represents the molecular relaxation time that is to be determined by a suitable spectroscopic experiment. – Application to far‐infrared (FIR) absorption spectroscopy is made explicitly. The above formula allows for a surprising interpretation of the well‐known anomalous temperature dependence of the FIR bands from first principles. The “size” of the dissipative structures that contribute to the FIR absorption in liquids is estimated.
Electron Excitation and Chemical Steps during Anodic Decomposition of n‐GaAs Electrodes: A Hole Injection Study
Authors: Vanmaekelbergh D. , Kelly J. J. , Lingier S. , Gomes W. P. 
Published: March 2014

AbstractThe contribution of electron excitation to the anodic dissolution of the n‐GaAs electrode was studied quantitatively by measuring the increase in the anodic blocking current when hole‐injecting agents such as Ce4+ or Fe(CN)3−6 were added to the electrolyte solution. The experimental relationship between the anodic current and the cathodic hole injection current was interpreted on the basis of the anodic decomposition mechanism, including a chemical step, proposed previously to explain stabilization results. This mechanism is complemented by an electrochemical step involving electron excitation from a decomposition intermediate occurring in parallel to the chemical step.
The Pressure Dependence of Self Diffusion in Supercooled Light and Heavy Water
Authors: Prielmeier F. X. , Lang E. W. , Speedy R. J. , Lüdemann H.‐D. 
Published: March 2014

AbstractMeasurements of self‐diffusion coefficients D in H2O and D2O at pressures up to 400 MPa and temperatures down to 200 K are reported. Upon cooling molecular motions are strongly retarded leading to a pronounced non‐Arrhenius temperature dependence of D. In contrast, initial compression of cold water facilitates translational and rotational motions. Unexpectedly, the rates of translational diffusion increase less dramatically than those of rotational diffusion. These results are discussed in relation to the peculiar structure of the hydrogen bond network of cold water. Further all dynamic isotope effects can be removed by shifting all temperature scales by ∼ 7 K in going from H2O to D2O.
Correlation of Second Virial Coefficients of Pure Components and Mixtures
Authors: van Nhu Nguyen , Kohler Friedrich 
Published: March 2014

AbstractA correlation is given for second virial coefficients on the basis of one‐center Lennard‐Jones potential parameters, which are determined from vapour pressure and orthobaric liquid densities. The anisotropy of the molecules is taken into account via Pitzer's acentric factor. The correlation works well when the preferred orientations are not too different between liquid and gas, i.e. when dipole moments are practically absent and when the acentric factor is smaller than 0.35. For liquid mixtures the unlike interaction is adjusted via the equimolar excess Gibbs energy. This procedure enables the correction for gas phase nonideality in vapour‐liquid equilibria measurements.
Scaling of Shear Viscosity of Nitro‐benzene/Isooctane Mixtures in the Critical Region
Authors: Jaschull G. , Müller‐Kirschbaum Th. , Woermann D. 
Published: March 2014

AbstractResults of measurements of the temperature dependence of shear viscosity of seven nitro‐benzene/isooctane mixtures of different compositions in the critical region are reported. The analysis of the viscosity data of the mixture of the critical composition in terms of critical exponent gives a value of φη = 0.048 ± 0.001. It is higher by about 20% than the theoretical value based on dynamic renormalization group theory calculations. The shear viscosity data of the non‐critical mixtures are in agreement with the scaling concepts of critical phenomena.
The Electrochemical Behaviour of Iron(II/III) on NAFION Coated Electrodes
Authors: Ye Jianhui , Doblhofer Karl 
Published: March 2014

AbstractThe redox‐system Fe2+/3+ in aqueous H2SO4 electrolytes was investigated with platinum electrodes coated with a perfluorosulfonate polymer (“Nafion”). The partitioning of the redox ions into the membrane‐type coating can be described by a classical ion‐exchange mechanism involving largely electrostatic forces. The apparent heterogeneous charge‐transfer standard rate constant was determined by a transient impedance technique in 0.05 to 0.5 M H2SO4 to be of the order of k0′ ≈ 1 · 10−3 cm s−1. At the lower H2SO4 concentrations the analysis of the charge‐transfer kinetics was not conducted because in this case the redox‐ion transport does not proceed by a simple diffusion mechanism. The diffusion coefficients of the redox ions in the membrane are of the order of 10−7 cm2 s−1. The known phase‐separation phenomena of the considered polymer are not noticeable in the electrochemical behaviour of the coated electrodes in this electrolyte.
Modell zur Berechnung von Kapazitäten bei Bleiakkumulatoren mit festgelegtem Elektrolyten
Authors: Teutsch U. , Böttcher F. , Winsel A. 
Published: March 2014

AbstractThe discharge capacity of a lead‐acid accumulator with immobilized electrolyte is essentially limited by depletion of sulfuric acid in the porous positive electrode. A rather simple macrohomogeneous, one‐dimensional model including consumption, migration and diffusion of sulfuric acid is used to predict discharge capacities as a function of cell parameters, temperature and discharge current density. Calculated capacities agree satisfactorily with experimental data if the final voltage is approximately 350 mV lower than the initial voltage. In addition to these numerical calculations a simple analytical function to approximate discharge capacities is given. The capacity calculations can be completed by another analytical function that gives an estimate of the change of capacity when a different final voltage is applied. The model calculations facilitate the development of new lead‐acid cells designed for special requirements.
Laser Induced Electrical Transients at Semiconductor Electrodes
Authors: Willig F. 
Published: March 2014

AbstractLaser‐induced electrical transients (LET) are described in a model with two capacitors in series, two current source terms, a measuring resistor, and a resistor for the system. Calculated and experimental LET signals at semiconductor electrodes are shown for characteristic kinetic situations in three different time windows t < τ, t comparable to τ, and t > τ, where τ represents the RC response time of the circuit.
The Underpotential Deposition of Lithium Ions from Acetonitrile Solutions with Small Amounts of Water
Authors: Gerischer H. , Wagner D. 
Published: March 2014

AbstractVoltammetric and coulometric studies have been performed of the underpotential deposition of Li+ ions from solution in acetonitrile. This process does not result in a Li monolayer if only small amounts of water are present. The deposited lithium reacts with water, primarily forming a LiOH layer. Underneath this layer, further Li+ reduction leads to the formation of a lithium hydride. This hydride with an excess of Li can in parallel form a lithium gold alloy. The reoxidation of the lithium hydride results either in the formation of Li+ ions and hydrogen or Li+ and H+ ions depending on the oxidation potential.
Photoelectrochemical Study on the Ternary Semiconductors AgInS2 and AgInSe2
Authors: Odenweller T. , Grabner E. W. 
Published: March 2014

AbstractPolycrystalline samples of the ternary semiconductors AgInS2 and AgInSe2 are prepared by melting of the elements in quartz ampoules and characterized by physical and electrochemical methods. A maximum photovoltage of 0.28 V for AgInS2 and a maximum photocurrent of 10 mA/cm2 for AgInSe2 are observed using a light intensity of 34 mW/cm2 (250 W halogene lamp). Action spectra suggest a direct transition to occur in AgInSe2 and an indirect one in AgInS2. A photoelectrochemical cell with AgInSe2 as photoanode, Pt as counter electrode, and I−3/I− in H2SO4 (pH 2) as electrolyte reveals a conversion efficiency of 1.6%.
Impedance Measurements on Illuminated p‐Indiumphosphide During Hydrogen Evolution
Authors: Kühne H.‐M. , Schefold J. 
Published: March 2014

AbstractImpedance measurements are presented on single crystalline, illuminated p‐type indiumphosphide photoelectrodes. The experiments show a shift of the flatband potentials towards more negative values during photoevolution of hydrogen. This shift amounts, both in acid and alkaline solution, to about −0.7 V at AM1, if no catalyst is deposited on the electrode surface. After platinum deposition, differences in the flatband potential are reduced to less than 100 mV, accompanied by a positive shift of the photocurrent onset for hydrogen evolution. – The results are interpreted in terms of electron trapping at the semiconductor‐electrolyte interface. The rate of charge transfer to the electrolyte (hydrogen evolution) is increased by platinum deposition, resulting in a decrease of the steady state concentration of trapped minority carriers. The model is linking the measured flatband potential shift under illumination to the kinetic overvoltage of multielectron transfer reactions at the semiconductor surface.
Multilayer Adsorption
Authors: Ruiz J. De D. Casquero , Guil J. M. , Masiá A. PÉRez , Paniego A. Ruiz 
Published: March 2014

AbstractUsing an exponential distribution function for the energy of the adsorption sites on a heterogeneous surface, an equation for multilayer adsorption is obtained. The basic assumptions are similar to those of the Frenkel‐Halsey‐Hill model (FHH). The equation deduced here is however somewhat different: a (θ + B)r term appears instead of the FHH θr term, where θ is the coverage, B is a constant related to the parameters of the exponential distribution function, and r is the exponent governing the decrease of energy with increasing distance from the surface. The addition of constant B to θ improves the linearity of the usual logarithmic plot of the equation and increases the value of r as compared with that from the FHH equation. The model is applied to the analysis of adsorption isotherms of N2 at 77 K on SiO2 and Sc2O3. Values obtained for r are close to 3, the theoretical exponent for the interaction due to dispersion forces.
Interrelations Between Thermodynamic Equations of State of Single‐ and Multi‐Component Adsorbates
Authors: Keller J. U. 
Published: March 2014

AbstractInterrelations of thermodynamic equations of state of adsorbed phases are considered. These relations are consequences of the fact that an adsorbate, assumed to be a thermodynamic system in the sense of Schottky, has a number of degrees of freedom which compared to that of a bulk phase is reduced by one. Depending on the choice of independent variables several forms of these interrelations can be formulated. Here especially relations between the adsorption isotherms of a multi‐component adsorbate, using the partial pressures and the temperature of the surrounding adsorptive as independent variables are considered. By these relations the number of independent parameters included in the isotherms is reduced considerably. This is demonstrated by discussing multi‐component adsorption isotherms of the Langmuir‐Freundlich – and of a generalized BET‐type.
Time Evolution of the Potential Distribution in Earth Alkaline Titanates under de Voltage Stress
Authors: Raith A. , Reijnen P. , Waser R. 
Published: March 2014

AbstractEarth alkaline titanates which are commonly used as dielectrics in ceramic capacitors may exhibit a long‐term degradation of the insulation resistance under simultaneous dc field and temperature stress. In order to study the nature of this process, it is necessary to detect the time evolution of the potential distribution between anode and cathode. A method is introduced which allows the determination of the potential distribution by the electrostatic deflection of an electron beam close to the edge of a current‐carrying sample. The results are used to evaluate various models which have been proposed to explain the mechanism of the degradation process.
Electrochemical Grafting of Poly‐3‐Methylthiophene on Platinum in Acetonitrile Studied by In‐Situ Ellipsometry and Electrochemistry
Authors: Lang P. , Chao F. , Costa M. , Lheritier E. , Garnier F. 
Published: March 2014

AbstractThe first steps of the electropolymerization of methyl‐3‐thiophene on polycrystalline platinum electrode in acetonitrile‐LiClO4 has been analysed, using in‐situ differential ellipsometry and rotating disk voltammetry. The optical method showed that the first step is the formation of oligomers in the solution. These oligomers precipitate onto the electrode surface when they reach a minimum length corresponding to a trimer, forming then nuclei. The polymer chain growths then by coupling with the newly electrogenerated radical cations. The rotating disk electrode study shows the influence of the forced convection on the grafting which under limit conditions, doesn't occur.
Zones of Sparingly Soluble Inorganic Salts with Membrane Properties in Gels
Authors: Choi Jung‐Gyun , Newrzella D. , Woermann D. 
Published: March 2014

AbstractPolyacrylamide gels containing potassium oxalate (sodium oxalate) are brought into contact with aqueous solutions of Pb(NO3)2, CaCl2, SrCl2 and BaCl2 respectively. The electrolyte concentrations in the gel phase and in the solutions are varied systematically. There exists a system specific characteristic concentration c̃s below which advancing precipitation zones of PbOx, CaOx, SrOx, and BaOx (Ox: oxalate) within the gel are observed. Above c̃s the precipitation zones do not grow after advancing for about 2 mm maximally. Such precipitation zones have membrane properties (e. g. Impermeability to ions forming the precipitate, osmotic property). c̃s corresponds to a supersaturation ratio of the order 103. The experiments indicate that the precipitation zones with membrane properties are generated by homogeneous nucleation. – The kinetics of formation of oxalate precipitates in cellophane skins is studied by measurements of the membrane potential as function of time. In these systems precipitate is formed by interdiffusion of two solutions containing the appropriate ions. A system specific delay time Δtdel is observed after which the precipitation zones acquire membrane properties. It is found that this time is related to the rate of formation of precipitate which is a function of the solubility product and the square of electrolyte concentration. The precipitation zone acquires membrane properties as soon as the local concentration of precipitate has reached a value of the order 10−3 mol cm−3. The existence of the characteristic concentration c̃s and of the delay time Δtdel are interpreted in terms of an absorption charge model proposed by Hirsch‐Ayalon.