bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Investigation of the Methanol Decomposition Behind Incident Shock Waves
Authors: Dombrowsky Ch. , Hoffmann A. , Klatt M. , Gg. Wagner H. 
Published: July 2012

AbstractThe pyrolysis of methanol was investigated behind incident shock waves at temperatures and densities between 1400 and 2200 K and 1 · 10−6 and 5 · 10−6 mol/cm3, respectively. Narrow band‐width laser absorption for OH radicals and ARAS technique for H atoms was used to determine the decomposition channels. For the experimental conditions described above the direct OH‐formation is found to be the main channel of about 80% of the decomposition rate. The channel leading to H and CH2OH is found to be less than 5%. There remains the possibility of channels leading from methanol to 1CH2 + H2O or to CH2O + H2.
Rate Constants for the Reactions of N2(A3Σu+,v′) with O3(X̃1A1)
Authors: Böhmer E. , Hack W. 
Published: July 2012

AbstractThe gas phase reaction of N2(A3Σu+) with O3(X̃1A1) was studied in a fast flow reactor. N2(A) was prepared by the energy transfer reaction of N2(X) with Ar* and detected by laser induced fluorescence (LIF) in the first positive system. From the depletion of N2(A,v′) as a function of the reactant concentration under pseudo‐first order conditions [N2(A)]0 < [O3], the overall rate constants of the reaction N2(A,v′ = 0,1,2, and 3) + O3(X̃1A1) → products for the specific vibronic states were determined to be: k(v′ = 0) = 2.5, k(v′ = 1) = 2.5, k(v′ = 2) = 4.8, k(v′ = 3) = 6.1 (in 1013 cm3/mol·s) at T = 298 K.—The products NO(X2Π) and O(3P) formed in the elementary reaction (1) were detected by LIF via the transition (A2Σ+ – X2Π) and by resonance absorption (RA), respectively.
Catalytic CO Oxidation over La1‐xSrxMnO3 at High CO Partial Pressures
Authors: Jaenicke S. , Chuah G. K. 
Published: July 2012

AbstractThe catalytic CO oxidation over polycrystalline LaMnO3 exhibits a bistability at high CO concentration. Under atmospheric pressure, the regime of bistability extends from 200 to 220°C and widens with increasing CO concentration. A systematic study of the solid solution system La1‐xSrxMnO3 which crystallizes in the perovskite structure, shows that the width of the bistable regime decreases with an increasing amount of strontium substitution and no bifurcation was observed for x > 0.2. A model is proposed to explain the bistability, based on a CO‐driven reconstruction of the reduced surface, leading to pairs of Mn2 ions with a Mn‐Mn distance comparable to the spacing in the metal. These pairs provide reactive sites for CO oxidation and oxygen chemisorption. Such metal‐metal pairs are not found in the perovskite lattice but are a structural feature of the closely related hexagonal 4‐layered packing which is the normal crystal structure of SrMnO3. The rate of change back to the “oxidized” surface is found to correlate with the lattice oxygen mobility. With low oxygen mobility, the transition from the active into the less active state becomes slow and hysteresis may result. Strontium substitution increases the number of defects in the oxygen lattice and leads ultimately to an oxygen deficiency (reductive nonstoichiometry). The catalytic activity of the system peaks at x = 0.2, indicating the influence of both the oxygen mobility and the oxygen nonstoichiometry on the catalytic oxidation reaction.
Suspension Structures of Deionized Colloidal Silica Spheres As Studied by the Reflection and Transmission Spectroscopy
Authors: Okubo Tsuneo 
Published: July 2012

AbstractStructural distributions of colloidal silica spheres are studied from the reflection and transmitted‐light spectrum measurements. The crystal‐like structures are suppressed when the sphere size is small and/or monodispersity index (standard deviation of the diameters divided by the mean diameter) is large; monodisperse (0.05 to 0.13 in monodispersity index) and large spheres (100 to 192 nm in diameter) give sharp peaks in the reflection and transmitted‐light spectra, which supports the existence of the crystal‐like structure in the suspensions. When the suspensions are diluted, phase transition toward liquid‐like distribution occurs. On the other hand, the deionized suspensions of polydisperse (0.20 and 0.21 in monodispersity index) and large spheres (133 to 148 nm in diameter) display the amorphous solid‐like distributions, and crystal‐like structures are not observed at any concentrations examined. By dilution the structure is transformed to the liquid‐like one. The crystal‐like and amorphous solid‐like distributions are melted out into the liquid‐like structures by the addition of a small amount of sodium chloride. The intersphere distances (D) decrease in the course of the melting. The transmitted‐light spectra for the suspensions of small spheres (45 nm in diameter) show the single broad peak, which supports liquid‐like distribution of the spheres. The D‐values of both crystal‐like and amorphous solid‐like structures agree with the mean distances calculated assuming that the spheres distribute homogeneously throughout the suspension. These results are consistent with the effective hard‐sphere model.
Reactivity of HO2· Radicals in Alcohols
Authors: Keszler Ágnes , Irinyi György , Héberger Károly , Gál Dezsö 
Published: July 2012

AbstractPhotoinitiated liquid phase oxidation of 1‐phenyl ethanol and benzyl alcohol have been investigated in the temperature range of 50–70°C using the intermittent illumination (rotating sector) technique. The rate of oxidation was followed by gas chromatography while the rate of initiation was determined by the inhibitor method. Results were explained by assuming HO2· radicals to be the main chain carriers, supported by comparison of the results with literature data. – The termination rate constant of HO2· was calculated from the average lifetime of radicals in both alcohols:2kt = 9.91 · 1012 exp(–29.2 kJ · mol−1/RT) in 1‐phenyl ethanol and2kt = 8.98 · 1012 exp(–31.3 kJ · mol−1/RT) in benzyl alcohol.(in 1 · mol−1 · s−1, the uncertainties given by the covariance matrix, see in the text.) – The rate constants for hydrogen abstraction by HO2 from the substrate molecules have also been determined in the case of both alcohols:kp = 4.61 · 108 exp(–52.0 kJ · mol−1/RT) in 1‐phenyl ethanol,kp = 1.04 · 109 exp(–54.3 kJ · mol−1/RT) in benzyl alcohol,(in 1 · mol−1 · s−1, uncertainties see in the text.)
Photoinduced Back Electron Transfer within Geminate Radical Ion Pairs. Observation of the Marcus Inverted Region in the System Thionine with Several Aromatic Donors
Authors: Grampp Günter , Hetz Gabriel 
Published: July 2012

AbstractThe Marcus “Inverted Region” is found for back electron transfer reactions within geminate radical pairs consisting of triplet‐thionine and several aromatic donors. Measurements were performed in buffered methanol (pH = 8.6) at 295 K. The standard free energy change ΔG−et0 ranges from –54.0 to –150.5 kJ/mol by varying the donors from N,N,N′,N′‐tetramethyl‐p‐phenylendiamine, p‐phenylendiamine, p‐aminodiphenylamine, 1‐naphthylamine, diphenylamine, 9,10‐dimethylanthracene, 1,2,4‐trimethoxybenzene to 9‐methylanthracene. The rate constants start at 3.3 · 107 s−1, reach a maximum at 1.0 · 109 s−1 for 1‐naphthylamine and decrease to 1.7 · 108 s−1 for highly exergonic reactions.
Mass Spectrometric Study of Volatile Products During the Carbochlorination of Zirconia
Authors: Pasquevich Daniel M. , Amorebieta Valentín T. 
Published: July 2012

AbstractThe reaction of chlorine with zirconium oxide in the presence of carbon was studied by mass spectrometry. Volatile reaction products were measured at different temperatures and traces of oxygen were detected. We also observed that the CO2/CO ratio increases with increasing reaction temperature. The role of the Boudouard reaction in the carbochlorination process is discussed and a reaction mechanism based on chlorine atoms is suggested.
Study of Forces of Inertia Acting on the Aqueous Pore Fluid of Polyelectrolyte Gels with Negatively Charged Fixed Ionic Groups
Authors: Röttger H. , Woermann D. , Rickert H. , Kappelhoff Th. 
Published: July 2012

AbstractIt is demonstrated that pulses of the inertia‐electromotive force can be generated during the deceleration of stiff rods of water containing Polyelectrolyte gels with negatively charged ionic groups covalently bound to the gel matrix. The counter ions of the fixed charges are silver ions. Two types of gels are used for the experiments. The concentration of the fixed ionic groups of gel type 1 is larger than that of gel type 2. The value of the ratio (m/e)exp (m, e, mass and charge of one silver ion respectively) calculated from the experimentally determined voltage puls ∫ U dt (U, inertia‐electromotive force; t, time) during the deceleration with gel type 1 is nearly a factor of 4 larger than the corresponding value calculated from corresponding experiments with solid ionic conductors (e.g. RbAg45). For the gel type 2 this factor has a value of about 20. The larger values of (m/e)exp found with the gels are attributed to a larger effective mass of the silver counter ions. During deceleration, the aqueous pore fluid together with hydrated mobile silver ions is shifted relative to the hydrated stiff matrix of the gel. This situation is different from that encountered in ion conductors in which the naked mobile silver ions are shifted relative to the rigid lattice formed by the anions during deceleration.
The Role of the Microstructure of Copper Deposits During Electroless Plating in Formaldehyde Containing Alkaline Baths. Comparison of Fourier Transform Impedance Spectroscopy and Surface Enhanced Raman Spectroscopy
Authors: Bittner Alexander , Wanner Michael , Weil Konrad G. 
Published: July 2012

AbstractThe microstructure of copper deposits was in‐situ investigated by impedance measurements and by surface enhanced Raman scattering. The simultaneous determination of the copper deposition rate with a quartz microbalance and the mixed potential under electroless plating conditions allows to separate the two partial processes copper deposition and formaldehyde oxidation. Due to this combination of investigation techniques we are able to correlate responses of the partial processes e.g. caused by variation of the bath components on changes of the surface microstructure of the copper deposit. A microstructure with amplitudes of an atomic scale is only maintained during the electroless deposition process and is a specific catalyst for formaldehyde oxidation. The overall process is found to be a complex heterogeneously catalyzed system, which can be understood in synergetic terms as a selforganizing process.
Phase Behavior and Light Scattering of the System Dodecyldimethylaminoxide, n‐Hexanol and Water in the Very Dilute Region
Authors: Platz G. , Thunig C. , Hoffmann H. 
Published: July 2012

AbstractSolutions of Dodecyldimethylaminoxide (DDMAO), n‐hexanol and water show a phase behavior which is found to be typical for many surfactant‐alcohol‐water systems with lamellar phases. Three types of lamellar phases and three types of isotropic low viscous clear phases which exhibit extreme flow birefringence (L3‐phases) are found at room temperature. Both a hexanol‐rich (Lαh) and a hexanol‐poor lamellar phase (Lαl) can be diluted to iridescent solutions with bright colors. The iridescent Lαh phase is of low viscosity and forms quickly, the higher viscous Lαl phase needs 600 hours until the iridescence can be observed. — UV‐Vis and classical light scattering measurements show that the interlamellar structures or spacings of the Lαl phase are strongly and those of the Lαh phase are weakly fluctuating. The Lαh phase is much more sensitive to added electrolyte than the Lαl phase. The Lαl phase seems to be the type of iridescent phases which can be found with some ionic surfactant‐water systems. — An intermediate lamellar phase exists between the Lαh and the Lαl phase with a second order or kinetically controlled phase transition. At the lower concentration limit (DDMAO concentration around 50 mmol/l) this intermediate phase needs several months for the formation. — The Lαh phase is accompanied at some higher hexanol concentration by a L3 phase. This phase transforms quickly to an iridescent phase immediately after shear stress. Depending on concentration and temperature this iridescent phase remains stable for a few minutes to several hours. The second isotropic phase with extreme flow birefringence exists below the Lαl phase. Dilution of the intermediate lamellar phase leads to an intermediate phase of type L3 which is not in a thermodynamic equilibrium state. — The Lαl phase and the intermediate lamellar phase give slow torsion waves whose propagation can be observed between crossed polarizers. The rheologic behavior which leads to these shear waves is discussed.
Investigation of 22Na Tracer Diffusion Through a Cation‐Exchange Membrane Using a Coincidence Counting Method
Authors: Daniel Thomas , Löhr Helge , Seidel Wolfhart , Sattler Ernst Ludwig , Seibold Georg 
Published: July 2012

AbstractBy means of e+ pair annihilation radiation the diffusional transport of 22Na ions through a poly‐phenol sulfonate (PPS) membrane was observed continuously using a coincidence counter device. Compared to usual tracer methods the present one has several advantages, e.g. appreciable smaller amount of solution and less total time for an experiment. — For different salt concentrations the apparent self diffusion coefficient of 22Na+ ions was determined.
Excimer and Isomer Mediated Reactions in Ionized van der Waals Clusters
Authors: Märk T. D. , Foltin M. , Grill V. , Rauth T. , Walder G. 
Published: July 2012

AbstractElectron impact ionization of rare gas clusters Rn (Nen, Arn) has been found to result via multiple collisions of the incoming/outgoing electrons in the production of cluster ions R containing R excimers. Radiative decay of these excimers leads to violent fragmentation of the respective cluster ions. Energetics, kinetics and dynamics of these reactions will be discussed. Moreover, a new technique – cluster autoscavenging spectroscopy – based on the excitation of neutral electronic states in the production process of mixed cluster anions (e.g. (XeSF6)−, (ArO4)−, (ArO3)−) will be introduced. Finally, a novel metastable decay reaction – observed for ionized hydrocarbon clusters of propane and butane – originating from an isomerization reaction of a single ion constituent within the cluster (e.g. C3H7+ and C4H7+ respectively) will be presented.
Chemical Reactions in Molecular Cluster Ions
Authors: Stace A. J. 
Published: July 2012

AbstractThe promotion and observation of chemical reactions in molecular cluster ions is discussed in terms of results from three recent experimental studies. The presence of “magic numbers” in cluster ions of the type Arn · X+, where X is either a reactant or fragment ion, provides evidence of molecules occupying sites on or close to the surface of a cluster. Results from experiments on excitation transfer are used to discuss the possibility that a single chemical reaction in an ion Y+, could be promoted through the selective excitation of a host cluster of the form XnY+. Finally, results are present from a new experiment designed to study laser‐induced chemical reactions in mass‐selected cluster ions. Preliminary data are given for photoinduced reactions in cluster ions of 1,3‐butadiene.
The Structure of Mixed Reactive Aggregates Studied by the Combination of IR Depletion and Resonant Two‐photon Ionization (R2PI) Spectroscopy
Authors: Riehn Ch. , Lahmann Ch. , Wassermann B. , Brutschy B. 
Published: July 2012

AbstractWe report on a molecular beam experiment combining the methods of IR depletion and resonant twophoton ionization (R2PI) spectroscopy. Mixed molecular aggregates of fluorobenzene (FB) and methanol (MeOH), viz. (FB)(MeOH) and (FB)(MeOH)2, are characterized. After photoionization these clusters show size‐dependent reaction channels. By comparing our IR depletion spectra with those of free methanol aggregates an assignment of the neutral precursors is feasible. For the system in question, the (1:2) aggregate is identified as the neutral precursor for both, the fragmentation product (1:1)+ and the reaction product anisole+.
Correlated‐Pair Fragmentation and Charge‐Transfer of CO2 Clusters from Atom‐Specific 1s Core Level Excitation
Authors: Dietrich H.‐J. , Jung R. , Waterstradt E. , Müller‐Dethlefs K. 
Published: July 2012

AbstractCorrelated pair fragmentation processes, for C 1s core level excitation of free CO2 molecules and CO2 clusters, have been investigated by “Zero Kinetic Energy” (ZEKE) electron spectroscopy and a (triple) ZEKE electron‐ion‐ion coincidence technique. For free CO2, the main fragmentation channels observed are the correlated ion pairs C+/O+, O+/O+, O+/CO+. These correlated pairs of cations originate from fragmentation of a CO2 dication which is formed by Auger‐type relaxation of the primary 1 s−1 core hole state. Surprisingly, for CO2 clusters this fragmentation channel is quenched, and correlated pair formation between intact cluster ions, i.e. CO2+/CO2+, CO2+/(CO2)2+ and (CO2)2+/(CO2)2+, become the dominant channels. This observation is explained by a fast charge transfer within the cluster, leading to redistribution of the two positive charges. For excitation to the CO22πu(π*) resonance, a possible mechanism for this intra‐cluster charge transfer is the participator valence Auger process following Auger core hole relaxation.
Decay Kinetics and Binding Energies of Benzene Clusters
Authors: Krause Harald , Ernstberger Bernhard , Neusser Hans Jürgen 
Published: July 2012

AbstractDissociation energies for monomer evaporation from small (n ≤ 4) neutral and ionized molecular clusters are experimentally determined from the measured ionization potentials and the appearance potentials of the respective metastable decay channels of each cluster ion. The results strongly support a sandwich structure for benzene dimer and trimer ions. For larger benzene cluster ions up to n = 23 the dissociation energies are deduced from the measured intensities of their metastable decay applying the evaporative ensemble model combined with a restricted RRKM formalism. The dissociation energies are discussed as a function of cluster size and interpreted in terms of the interaction mechanism and the structure of the complex.
Electronic Structures and Related Properties. Electron Impact Ionization Potentials of Gold and Silver Clusters Men, n ≤ 22
Authors: Jackschath C. , Rabin I. , Schulze W. 
Published: July 2012

AbstractSmall noble metal clusters were produced by a gas aggregation technique and were investigated mass spectrometrically using electron ionizing energies ranging from 100 eV down to the threshold region. For energies above approximately 20 eV electronic effects are displayed, that characterize a stable cationic distribution, i.e. enhanced stability is found for odd numbered clusters posessing an even number of electrons, furthermore, shell closing appears at n = 3, 9, 21… On the other hand, the electronic effects found while investigating the threshold energy region have to be attributed to neutral clusters, i.e. even numbered clusters are more stable.–The vertical ionization potentials in this region clearly demonstrate the manifestations of shell effects as well as distinct even‐odd oscillations. For both Ag and Au a dramatical drop in the ionization potential is observed from dimer to trimer. The overall size‐dependence of the ionization energies differs from that of alkali clusters due to the presence of d‐electrons.
Electronic Supershells in Metal Clusters
Authors: Genzken O. , Brack M. , Chabanat E. , Meyer J. 
Published: July 2012

AbstractWe present selfconsistent calculations of the supershell structure of sodium, lithium, indium and aluminium clusters, by using the spherical jellium model in LDA and solving the Kohn‐Sham equations for up to N ≈︁ 3000 electrons. While the agreement with the experimental results is very good for alkali metal clusters (Na and Li), it is rather poor in the case of aluminium. We also present quantum‐mechanical calculations for a recently suggested phenomenological Woods‐Saxon potential for the valence electrons of aluminium clusters.
Theory for the Ionization Potential of Clusters of Rare Gas Atoms
Authors: Stampfli P. , Bennemann K. H. 
Published: July 2012

AbstractWe present a theory for the ionization potential of clusters of rare gas atoms. It accounts for the polarization of the rare gas atoms and the delocalization of the hole. Results for the vertical ionization potential are obtained for very large cluster sizes. A comparison with experiments indicates that a gradual size‐dependent transition from adiabatic ionization (for small clusters) to vertical ionization (for bulk and large clusters) has been observed.
High‐Resolution UV Spectroscopy of Molecular Complexes
Authors: Neusser H. J. , Sußmann R. , Smith A. M. , Riedle E. , Weber Th. 
Published: July 2012

AbstractInformation on the structure, the rigidity and the intermolecular potential of molecular complexes is essential to our understanding of the physical and chemical properties of molecular complexes. In this work we would like to demonstrate that rotationally resolved UV spectroscopy provides precise new information on these topics. In particular, the structure and van der Waals bond length of benzene‐X complexes (X = Ne, Ar, Kr, Xe, N2) have been experimentally determined. In the benzene‐N2 complex with its parallel‐stacked configuration, the two constituents, benzene and N2, can rotate against each other. Rotationally resolved vibronic van der Waals bands allow the clear assignment of the excited van der Waals vibrations. Their anharmonicity and the vibrationally averaged rotational constants provide basic information on the intermolecular potential. For the example of the benzene‐Ar2 trimer it is shown that isomeric structures exist that are rigid on the nanosecond time scale.
Kinetics of Formation and Vibronic Spectroscopy of H‐Bonded Clusters in Supersonic Jets
Authors: Wolf K. , Kuge H.‐H. , Schmitt M. , Kleinermanns K. 
Published: July 2012

AbstractMass‐selected two‐photon resonant ionization spectra of supersonically cooled p‐cresol · (H2O)n are reported. Cluster spectra with n = 1–4 water molecules attached can be unambiguously assigned. The excellent agreement between the experimental curves of cluster densities as function of H2O pressure and the corresponding calculated curves obtained from numerical integration of the master equation system assuming successive cluster formation further subsidizes the cluster size assignment.–The cluster spectra all lie on the red side of the monomer spectrum but exhibit an irregular red and blueshift relative to each other. Simple molecular orbital (HOMO‐LUMO) considerations based on ab initio calculations quantitatively show this to be due to the H‐bond induced change in the inductive effect of the phenolic O‐atom on the π*‐π transition. The oxygen atom of p‐cresol acts a proton donor in the n = 1 cluster and additionally as proton acceptor in the n = 2 clusters, while the H2O‐subunits in the n = 3 and 4 clusters form a cycle. These structures are further substantiated by extensive ab initio calculations and the measured H‐bond stretch frequencies in the S0 and S1‐state.