bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoionization and Photodissociation of Allene Clusters in a Supersonic Molecular Beam
Authors: Rühl E. , Brutschy B. , Bisling P. , Baumgärtel H. 
Published: March 2014

AbstractThe cluster photoionization mass spectrum of allene (1,2‐propadiene) (C3H4) has been measure with synchrotron radiation from the electron storage ring BESSY. Cluster cations and characteristic fragmentation patterns are observed which are differing depending on the cluster size. The allene dimer decays mainly into C3H5+ and C6H7+. The trimer fragmentation yields mainly C7H7+, C7H8+, and C8H9+. These cations are formed by abstraction of methyl, ethene, and ethyl groups, respectively. The parentage of the fragmentation products has been assigned by measuring the pressure dependence of the ion signals. The energetics of the ionization and fragmentation processes has been studied by means of appearance potential measurements. From these values intermolecular binding energies of the cationic complexes are obtained. The role of stable precursor cations and the evidence of energy barriers are discussed for the dominating cluster fragmentation reactions. The role of proton transfer reactions within allene clusters is discussed in terms of charge distributions obtained from MNDO calculations.
Intramolecular and Fragmentation Dynamics of Van der Waals Complexes
Authors: Wozny Christopher E. , Gray Stephen K. 
Published: March 2014

AbstractThe classical phase space dynamics of a simple two degree of freedom model for the vibrational predissociation (i.e. fragmentation) of van der Waals complexes is reviewed, with emphasis being placed on the role of transitions across intramolecular and intermolecular bottlenecks. A similar phase space picture is proposed to exist in van der Waals systems with three or more degrees of freedom. Evidence for this is presented with a 3D classical trajectory study of NeCl2 fragmentation. An approximate intermolecular bottleneck is explicitly constructed for this system.
Vector Correlations in Molecular Photodissociation: H2O2, HONO2 and (CH3)3COOH
Authors: August Julie , Brouard M. , Docker M. P. , Hodgson A. , Milne C. J. , Simons J. P. 
Published: March 2014

AbstractDoppler resolved, laser induced fluorescence spectroscopy has been established as a powerful probe for determining scalar energy distributions among primary photofragments. Measurements of the sensitivity to alternative excitation‐detection beam geometries and polarisations and the choice of the monitored rotational features, P↑, R↑ or Q↑ has now made LIF probing even more powerful, by revealing additional information on their momentum distributions. These are expressed in terms of a family of vector correlations: the translational anisotropy, the rotational alignment and the helicity. – New data are presented and analysed for three archetypal systems, H2O2, HONO2, (CH3)3COOH, each of which presents totally featureless U.‐V. absorption continua. Doppler resolved LIF spectroscopy of the recoiling OH fragments generated by laser photodissociation at 248 nm (H2O2, (CH3)3COOH) or 280 nm (HONO2) is used to assign the electronic transitions, the structural changes which follow excitation, and their influence on the intramolecular dynamics involved in the photodissociation process.
Dynamics of Molecular Photofragmentation
Authors: Comes F. J. , Gericke K. H. , Grunewald A. U. , Klee S. 
Published: March 2014

AbstractPhotodissociation dynamics provides a vast amount of information in understanding chemical dynamics. The obtained energy‐release data describe scalar properties of the chemical interaction which can be compared directly with the results of classical or quantum mechanical scattering calculations. However, even a complete knowledge of the product distribution provides only a limited view of the dissociation process, as long as vector correlations between observables are not taken into account. These correlations can be obtained by measuring Doppler profiles of the products using polarized light and different excitation and detection geometries. – The correlation between the transition dipole moment μ in the parent and the recoil velocity v of the fragment, as well as the correlation between μ and the rotational vector J of the product, may reveal the symmetry and geometry of the dissociative state. Any decrease in fragment anisotropy of directional properties caused by parent rotation gives information on the lifetime of the parent excited state. Very recently a substantial progress in the field of photodissociation dynamics has been achieved by observing not only the <μJ> and <μv> correlation but also the correlation between the rotational and translation motion of the fragment, <μJ>, and between μ, v, and J. – Observation of fragment anisotropy can also be used to discriminate between two different dissociation channels. If two electronic states are responsible for the dissociation process, the observed line shape is a linear combination of two Doppler profiles. The bipolar moments of the <μv> correlation for each contributing parent dissociation channel can be used to calculate the product state distribution referring to the two different fragmentation channels. As an example, the dynamics of the photofragmentation of the H2O2 and D2O2 is analyzed by a characterization of scalar and directed properties of the recoiling OH fragments.
Width Distributions for Random Interstate Coupling
Authors: Dietz W. 
Published: March 2014

AbstractDifferential probability distribution functions are calculated for the widths of oscillator carrying (light) states perturbed by statistically independent background states. Simple analytical expressions are given for the most probable value and fluctuation in case of dense or sparse background manifolds. In these limits the rescaled distributions are independent from model parameters. As example the model is applied to the 1410120 vibronic band of benzene. The results are compared with a previous, more specific model.
New Order Out of the Chaotic Bath of Highly Vibrational States of C2H2
Authors: Pique J. P. , Lombardi M. , Chen Y. , Field R. W. , Kinsey J. L. 
Published: March 2014

AbstractUsing a Statistical Fourier Transform (SFT) technique we show the first evidence of a very soft mode (5.5 cm−1) out of the chaotic vibrational spectrum of C2H2 at 26500 cm−1 above the ground state.
Multiphoton Ionization Studies of Energy Transfer in Highly Excited Ground State Molecules
Authors: Luther K. , Reihs K. 
Published: March 2014

AbstractA multiphoton ionization method, the “kinetically controlled selective ionization” (KCSI), is presented which is suitable for observations of the time evolution of molecular populations at selected vibrational energies even in cases of unresolvable high densities of states. In collisional energy transfer this technique allows the first experimental determination of 〈ΔE2〉, and therefore of a population distribution of highly excited molecules during the relaxation. In addition it provides sensitive detection of 〈ΔE〉, the average amount of energy transferred per collision, and its energy dependence. Examples of such measurements are shown and discussed.
A Proton Magnetic Resonance and Gravimetric Study of Water and Isopropanol Adsorption on Microcrystalline Rutile. II. Hydration and Hydroxylation
Authors: Boddenberg B. , Horstmann W. 
Published: March 2014

AbstractBy means of1H magnetic resonance the time domain line shapes of water adsorbed on a microcrystalline titania (rutile) at three different coverages were measured as function of temperature (77 to 350 K) and resonance frequency (21 to 90 MHz). Evidence is obtained that dissociation of chemisorbed water even on the (110) surface planes amounts to not more than about 33%. Except at the lowest coverage measured the spectra indicate rapid proton exchange processes to occur which average out the static dipolar interaction energy.
Photochemistry of Colloidal Semiconductors 28. Photo‐Electron Emission from Cadmium Phosphide Particles in Aqueous Solution
Authors: Haase Markus , Weller Horst , Henglein Arnim 
Published: March 2014

AbstractLaser illumination (308 nm) of small Cd3P2 particles in aqueous solution leads to the formation of hydrated electrons which are detected by their strong optical absorption. The yield increases with decreasing particle size. A quantum yield of 0.04 electrons per photon absorbed was observed for yellow Cd3P2. The absorption of the holes remaining was also observed. Trapped holes and electrons live several 100 ns on the colloidal particles, their recombination being accompanied by fluorescence. – The photo‐electron emission is a complex two‐photon process. A mechanism is proposed according to which an electron is emitted upon the interaction of the two excitonic states (electron‐hole pairs) produced by successive photon absorptions in a colloidal particle. The first state is already relaxed and acts as a fast recombination center for the delocalized second state, the recombination energy being used for the promotion of an electron into the aqueous solvent. This kind of photo‐electron emission thus follows a mechanism different from the two‐photon reactions yet known in laser photochemistry.
Measurements and Analysis of Excess Enthalpies of Alkyl Acetates + 1‐Chloroalkanes Using the Unifac Model
Authors: Ortega Juan 
Published: March 2014

AbstractMolar excess enthalpies at 298.15 K and atmospheric pressure are reported for eight binary liquid mixtures of alkyl (methyl and propyl) acetates + 1‐chloroalkanes (pentane, hexane, heptane and octane). The experimental results along with literature data of ethyl acetate with the same 1‐chloroalkanes are examined by a version of the UNIFAC model. In general, the model reproduces the experimental data within the limits of error. The maximum discrepances are observed in those mixtures where the acetate with the largest alkyl radical intervenes; however, the average overall error of the twelve systems analysed here is less than 6.5 per cent.
Recent Advances in the Theory of the Electric Double Layer
Authors: Schmickler Wolfgang 
Published: March 2014

AbstractRecent progress in the theory of the electric double layer at a metal/solution interface is reviewed. In the absence of specific adsorption the system may be represented as jellium in contact with an ensemble of hard sphere ions and dipoles; results of explicit model calculations are compared with experimental data. When ions are specifically adsorbed, the induced change in the surface dipole potential is of particular interest. Due to the effective screening of the adsorbate charge by the solvent and by the metal electrons, the corresponding dipole moments are relatively small. Finally, isotherms for ionic adsorption are considered in the limit of vanishing bulk concentration.
Thin Films of Conjugated Polymers for Photoelectrochemical and Electronic Devices
Authors: Garnier Francis , Horowitz Gilles , Roncali Jean , Lemaire Marc 
Published: March 2014

AbstractOrganic conjugated polymers can be deposited as thin films on semiconducting or conducting electrodes, and, owing to the large potential offered by varying their physical and chemical properties, new devices can be envisionned. Thus CdS and CdSe are interesting photoanodes for the photoelectrochemical conversion and storage of light energy, but they require to be protected against their very fast corrosion in aqueous solution. This is achieved by thin layers of composite conducting polymers, in which the conductivity the catalytic activity and the hydrophobic character can be controlled. Besides, conjugated polymer films possess in their undoped state semiconducting properties, and when deposited on inorganic semiconductors, they lead to new “organic‐on‐inorganic” electronic junctions. The electric characteristics of these junctions can be easily tuned by subtle chemical modifications in the polymer structure and doping level. Finally, the recent development of functionalized organic conducting polymers, in which various prosthetic groups bearing selective functions are homogeneously distributed along the conducting chains, will allow the realization of new chemically selective electronic devices.
Oxygen Reduction Electrocatalysis by Chevrel Phase Sulfides Supported on Carbon Paste Electrodes
Authors: Schubert B. , Vante N. Alonso , Gocke E. , Tributsch H. 
Published: March 2014

AbstractMolecular oxygen reduction studies in acid medium have been performed with cluster materials of the Chevrel phase type supported on carbon paste electrodes. It was found that the metal intercalated in the channels between Mo6 clusters enhances their catalytic activity. This is explained by the formation, during oxygen reduction, of peroxo intermediates bonded both to the transition metal cluster and to the intercalated atom. The advantage of the resulting bimetallic catalysis is even more pronounced using mixed clusters. The increasing activity of differently intercalated cluster materials can be correlated with their structural parameters.
Elektrochemie neuer Speichersysteme
Authors: Beck F. 
Published: March 2014

AbstractChemistry and material science predominate in the development of new storage batteries. Nevertheless, no perspective systematics is possible without the fundamental electrochemical aspects. The present review consequently tries to verify this feature and it generally avoids the descirption of individual systems. The industrial state of the art is characterized by energy densities of about 100 Wh/kg−1 and by satisfying cyclabilities.
Electron Spectroscopic and Electrochemical Investigations of Chemically Modified Iron Surfaces
Authors: Volmer M. , Czodrowski B. , Stratmann M. 
Published: March 2014

AbstractIron surfaces, chemically modified by n‐decanethiol (n‐DMc), have been investigated in order to get a better understanding of the corrosion protection of reactive metals by organic coatings, as investigations of the phase boundary substrate/organic coating are possible only if just monolayers of an organic monomere are adsorbed onto the metal. Electron spectroscopic (XPS, AES) and electrochemical analyses (cyclovoltammetry, rotating ring‐disc‐electrode) have shown that a stable bond between iron and n‐DMc and a well defined orientation of the organic molecules towards the surface are only observed, if the thiol is adsorbed at an oxid free substrate. In this case the oxidation of the thiol by air to disulfide, sulfenate, and sulfonate is highly inhibited. Similar results are obtained regarding the electrode reactions like metal dissolution/passivation, and H+‐reduction in an Ar‐purged borate buffer (pH = 8.5). Only oxygen can be reduced on the modified surface with high rates, the kinetics being completely different from the one on clean iron surfaces. It is proposed, that as part of the O2‐reduction the thiol is transformed into disulfide, which then catalyses the oxygen reduction but still inhibits the rate of metal dissolution and H+‐reduction. After prolonged O2‐reduction the disulfide is oxidized to sulfonate, which then desorbs from the metal surface.
Impedance Analysis of Quartz Oscillators, Contacted on One Side with a Liquid
Authors: Beck Ralf , Pittermann Udo , Weil Konrad G. 
Published: March 2014

AbstractWe use a vector analyzer to investigate the impedance of a quartz oscillator, one face of which is exposed to a liquid. An aqueous LiCl – solution can be used to vary density and viscosity of the liquid over a wide range. The solution acts as an additional impedance with as well a real as an imaginary part. Furthermore, different electrical driver circuits have been used to excite the crystal vibrations. In most cases, our experimental results deviate from the predicted dependence of the crystal frequency from density and viscosity. These deviations are different for different driving circuits, but they do not change with the properties of the liquid.
The Dependence of the Redox Potentials in the System Ru[(CnH2n+1)2bpy]23+/3+ /Methylviologen2+/+ on the Hydrocarbon Chain Length and on the Ratio of Water and Acetonitrile in the Solvent
Authors: Greiner G. , Wörner M. , Rau H. 
Published: March 2014

AbstractThe redox potentials of hydrocarbon‐substituted Ru[(CnH2n+1)2bpy]3 complexes with n = 0, 1, 5 and 7 have been measured with cyclic voltammetry in acetonitrile. There is a marked decrease of the redox potential on substitution but the chain length has no strong effect. The free enthalpy of electron transfer for the reaction between the oxidized complexes and reduced methylviologen RuL33+ + MV+ → RuL23+ + MV2+ has been obtained by differential pulse voltammetric measurements of the redox partners in the same solutions of different water/acetonitrile composition. The electron transfer is less exergonic for the substituted complexes and there is a minimum in the ΔG° vs. χ plots for the unsubstituted and methyl‐substituted complex. The effect of the supporting electrolyte on ΔG0 is shown for the methyl‐substituted complex. The relevance of these results for the photoinduced electron transfer reaction is pointed out.
Electrochemical and Structural Behaviour of Pd+ Implanted TiO2‐Films in Dependence on the Pd+‐Concentration
Authors: Elfenthal L. , Schultze J. W. , Delplancke J.‐L. 
Published: March 2014

AbstractAccording to our recent investigations, ion implantation into oxide films yields an increase in capacity, an enhancement of ETR and a decrease in the band gap. These effects are now measured in dependence on the implanted Pd+‐concentration. Due to doping or metallization by Pd as well as to radiation damage and amorphization, the implantation effects increase up to 1 to 3% Pd+ but then saturation is observed. Saturation of amorphization is due to fast annihilation of the Frenkel defects during implantation, but saturation of doping by Pd may be caused by the Pd‐cluster formation. The defect states of the oxide films can be annihilated during the andic polarization (repassivation). – The interface Ti/TiO2 is mixed by the implanted Pd+‐ions. The surface structure and grain boundaries of the oxide films disappear during Pd+‐implantation. This can be seen with Scanning Electron Microscopy and measured by localized photocurrent and Transmission Electron Microscopy. The implanted films are reconstructed by repassivation, and an additional oxide is grown at the interfaces of the oxide. The latter can be concluded from Rutherford Backscattering Spectroscopy (RBS). The Pd‐enrichment at the surface, at intermediate repassivation potentials, is measured by X‐ray Photoelectron Spectroscopy (XPS) and it can be correlated exactly with the results of ETR experiments. XPS ad RBS show that all implanted Pd+ disappears during repassivation up to the oxide formation potential.
Forces and Torques Acting on Two Parallel Dielectric Cylinders in a Periodic Transverse Field. B. Frequency Dependence
Authors: Schlögl Reinhard W. 
Published: March 2014

AbstractThe frequency dependence of forces and torques acting on two parallel cylinders in a periodic field is investigated. The permittivities are assumed to have imaginary parts a) due to an electric conductance or b) due to a single Debye relaxation. At the transition frequencies a change of the sign of the force components or of the torque can take place. Marked deviations from the “long distance laws” occur for small cylinder distances.
Photochemistry of Azide Complexes of Gold, Silver, Platinum, and Palladium. Generation of the Metallic State
Authors: Vogler A. , Quett C. , Kunkely H. 
Published: March 2014

AbstractThe photochemistry of the following azide complexes in organic solvents has been investigated: [Au(N3)4]−, [Au(N3)2]−, [Ag(PPh3)2N3], [Pt(N3)6]2, [Pt(N3)4]2−, [Pd(N3)4]2−, and [Pd2(N3)6]2−. All complexes underwent a photochemical reduction of the metal and oxidation of azide upon ligand to metal charge transfer excitation. The photolysis of the complexes with the metals in the lower oxidation states (Au(I), Ag(I), Pt(II), Pd(II)) led ultimately to the generation of free metals which form colloids. These colloids were characterized by their absorption spectra which showed the typical plasmon bands in the case of gold and silver. Pt(0) and Pd(0) produced during the photolysis can be intercepted with allyl chloride to form [Pt(π‐allyl)Cl]4 and [Pd(π‐allyl)Cl]2. Most photoreactions took place with rather large quantum yields.
Synthesis of highly luminescent mercaptosuccinic acid‐coated CdSe nanocrystals under atmospheric conditions
Authors: Dong Meiting , Xu Jingyi , Liu Shuxian , Zhou Ying , Huang Chaobiao 
Published: March 2014

ABSTRACTHere we report a facile one‐pot method for the preparation of high‐quality CdSe nanocrystals (NCs) in aqueous solution under an air atmosphere. Compared with the traditional use of NaHSe or H2Se, the more stable sodium selenite is utilized as the Se source for preparing highly luminescent CdSe nanocrystals. By using mercaptosuccinic acid (MSA) as the capping agent and borate–citrate acid as the buffering solution, CdSe nanocrystals with high quantum yield (up to 70%) have been synthesized conveniently. The influence of different experimental parameters, such as the pH of the precursor solution, the molar ratio of Cd2+ to Na2SeO3 and Cd2+ to MSA on the CdSe nanocrystals, has been systematically investigated. The prepared CdSe NCs were spherical with a size of ~ 5 nm. Copyright © 2014 John Wiley & Sons, Ltd.
Most lobular carcinoma in situ and atypical lobular hyperplasia diagnosed on core needle biopsy can be managed clinically with radiologic follow‐up in a multidisciplinary setting
Authors: Middleton Lavinia P. , Sneige Nour , Coyne Robin , Shen Yu , Dong Wenli , Dempsey Peter , Bevers Therese B. 
Published: March 2014

AbstractWe evaluated the efficacy of using standard radiologic and histologic criteria to guide the follow‐up of patients with lobular carcinoma in situ (LCIS), lobular neoplasia (LN), or atypical lobular hyperplasia (ALH). Patients with high‐risk benign lesions diagnosed on biopsy were presented and reviewed in a multidisciplinary clinical management conference from 1 November 2003 through September 2011. Associations between patient characteristics and rates of upgrade were determined by univariate and multivariate logistic models, and times to diagnosis carcinoma were calculated. Of 853 cases reviewed, 124 (14.5%) were lobular neoplasms. In all, 104 patients were clinically and/or radiographically monitored. In 20 patients, who were found to have LN on core biopsy and were recommended to have immediate surgical excision, a more significant lesion was identified in 8 (40%) of the excised specimens. Factors associated with a more significant lesion on excisional biopsy included whether the lobular lesion had been targeted for biopsy and whether the extent of disease involved three or more terminal duct lobular units. Of the 104 patients radiographically and clinically monitored, the median follow‐up time was 3.4 years with a range of 0.44–8.6 years. Five patients under surveillance were subsequently diagnosed with breast malignancy (three of the five at a site unrelated to the initial biopsy). Patients with incidental lobular lesions identified on percutaneous core needle biopsy have a small risk of upgrade and may not require an excisional biopsy. Clinical management of low‐volume lobular lesions in a multidisciplinary setting is an efficacious alternative to surgical excision when radiologic and histologic characteristics are well‐defined.