bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass Spectrometric Studies on the Vapour Phase Composition over Solid and Fused Cs3Sb
Authors: Busse Bernd , Weil Konrad G. 
Published: July 2012

AbstractKundsen cell mass spectrometric measurements are reported on the composition of the vapour over solid and fused Cs3Sb. The main constituents of the vapour are species which are also present over the pure metals, Cs, Cs2, Sb, Sb2, and Sb4. Besides these a number of signals are recorded which can be attributed to intermetallic molecules and their fragments. Careful studies of the ionisation curves for the different species made it possible to evaluate the complete fragmentation scheme. It leads to the conclusion that the following intermetallic species are present in the equilibrium vapour: Cs2Sb4, CsSb2, Cs2Sb, and Cs2Sb2. From that it can be concluded that the interactions which stabilize the compounds are different from those in the condensed phases, where Cs3Sb, CsSb, and Cs3Sb7 are congruently melting compounds.
Equation of State for Gaseous H2S
Authors: Rau Hans , Mathia Wolfgang 
Published: July 2012

AbstractPVT‐measurements on gaseous H2S up to 760 K and 600 bar were performed. The hot gas was in contact with silica only, so that no corrosion occurred. The results together with literature data were compared with equations of state, the parameters of which had been fitted by least‐squares‐methods. The Redlich‐Kwong‐equation is recommended for calculations, because values computed from this equation do not differ more from the measured values than those computed from equations with more than two parameters.
Proton Magnetic Resonance Study of Ligand Exchange on Tetrakis (Methylmethylphenylphosphinate) Beryllium(II) and Tetrakis (Dimethylmethylphosphonate) Beryllium(II) in Non‐Aqueous Solvents
Authors: Thaczuk M. N. , Lincoln S. F. 
Published: July 2012

AbstractLigand exchange on tetrakis(methylmethylphenylphosphinate)beryllium(II), [Be(mmpp)4]2+, and its dimethylmethylphosphonate analogue, [Be(dmmp)4]2+, has been studied in CD3NO2, CD3CN, and CD2Cl2 solvents using 1H (90 MHz) NMR methods. When the solvent is CD3CN or CD2Cl2 ligand exchange on [Be(mmpp)4]2+ exhibits a rate independence of [mmpp]free whereas when the solvent is CD3NO2 the ligand exchange rate = k2 4[Be(mmpp)2+4][mmpp]free where k2 (298.2K) = 0.22 ± 0.01 dm3 mol−1 s−1, ΔH≠ = 68.7 ± 0.9 kJ mol−1, and S≠ = −26.1 ± 2.7 J K−1 mol−1. When the solvents is CD2Cl2 ligand exchange on [Be(dmmp)4]2+ exhibits a rate independence of [dmmp]free whereas when the solvent is CD3CN the ligand exchange rate = 4(k1 + k2 [dmmp]free) [Be(dmmp)2+4] where k1 (298.2 K) = 0.93 ± 0.04 s−1, ΔH≠ = 64.3 ± 1.2 kJ mol−1, ΔS* = −29.7 ± 3.7 J K−1 mol−1, k2 (298.2 K) = 0.33 ± 0.05 dm3 mol−1 s−1, ΔH≠ = 69.4 ± 4.4 kJ mol−1, and ΔS≠ = ‐ 21.3 ± 13.1 J K−1 mol−1. These data are interpreted in terms of dissociative (D) and associative (A) ligand exchange mechanisms and the effect of the solvent on mechanism is discussed. An apparent ΔH≠/ΔS≠ isokinetic relationship is used as the basis of a comparison of the lability of beryllium(II) with other metal centres.
On the Interplay between Geometry and Mobility in Intramicellar Kinetics
Authors: Hatlee Michael D. , Kozak John J. , Grätzel Michael 
Published: July 2012

AbstractThe role of geometry in influencing reaction‐diffusion processes in spherical versus rod‐shaped micellar aggregates is studied. Previously‐reported data on pyrene excimer fluorescence in dodecylammonium chloride (DAC) micellar solutions is analyzed by applying a theory proposed by Adam and Delbrück to account for timing effects associated with the reduction of dimensionality in diffusion‐controlled processes. Our results show that the overall dynamics are governed by an interplay between the characterizing geometry of the host micellar aggregate and the mobility of the solubilized probe molecules in the assembly.
The Thermal Conductivity of Mixtures of Hydrogen with Nitrogen
Authors: Kestin J. , Nagasaka Y. , Wakeham W. A. 
Published: July 2012

AbstractThe paper reports absolute measurements of the thermal conductivity of mixtures of hydrogen and nitrogen in the pressure range 0.7 to 10 MPa at a nominal temperature of 27.5 °C. The experimental results have an estimated uncertainty of ±0.3%. The mixture thermal conductivity in the limit of zero‐density can be described with the aid of the available kinetic theory only if empirical adjustments are made to some of the collision‐integral ratios characteristic of the unlike interactions. The need for these adjustments is taken as evidence that the available kinetic theory formulae are not sufficiently accurate for gas mixtures in which the mass ratio of the molecules is large. At elevated densities the calculation scheme of Mason and his coworkers cannot provide a description of the experimental data within their uncertainty, even when empirical adjustments of a parameter characteristic of the unlike interactions are allowed.
Determination of the Rotational Correlation Time of Water by Proton NMR Relaxation in H217O and Some Related Results
Authors: Lankhorst D. , Schriever J. , Leyte J. C. 
Published: July 2012

AbstractAnalysis of the1H‐17O dipolar contribution to the proton longitudinal relaxation rate in17O‐enriched water yields a correlation time for re‐orientation of the O–H vector τrOH= (1.71 ± 0.07) ps in H2O at 25 °C. This result is insensitive to uncertainties in the calculated intermolecular relaxation contribution. From1H, D, and17O relaxation rates in H2O/D2O mixtures deuterium isotope effects on the correlation times were estimated. The quadrupole coupling constants of D and17O in liquid water were determined.
Distribution of Chloride and Bromide Counterions of Cetyltrimethylammonium Micelles in Water. A Fluorescence Study
Authors: Wolff Thomas , Von Bünau Günther 
Published: July 2012

AbstractRelative fluorescence intensities of anthracene, fluorene, and 9,10‐dimethylanthracene in aqueous solutions of cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC) have been measured as functions of surfactant concentrations. Fluorescence was found to be quenched by bromide but not by chloride ions. At low total concentrations (cs < 0.01 M) of CTAB/CTAC‐mixtures quenching efficiencies depend linearly on the CTAB‐mole fraction. Deviations from linearity are observed for higher cs‐values and attributed to preferential binding of bromide ions to the micelles. Additional deviations at cs > 0.3 M are connected with changes in micelle shape (rod formation).
Magnetic Circular Dichroism and Molecular Orbital Studies on the Intramolecular Charge‐Transfer Transitions in the Bridged Tropylium Cations
Authors: Tajiri Akio , Hatano Masahiro , Nakazawa Tomoo , Nakasuji Kazuhiro , Murata Ichiro 
Published: July 2012

AbstractThe magnetic circular dichroism (MCD) spectra of the bridged tropylium cations have been measured at room temperature. Very weak MCD bands have been observed in the longest wavelength region and assigned to the intramolecular charge‐transfer (CT) transitions arising from the electronic excitations from the highest occupied MO(HOMO) of the remote chromophore to the lowest vacant MO(LVMO) of the tropylium cation. In the shorter wavelength region, four distinct MCD bands with alternating sign have been detected, clarifying four π→π* transitions in the perturbed tropylium moiety.
Absorptions‐ und Fluoreszenzspektren sowie Dissoziationskonstanten der Grund‐ und ersten angeregten Singulettzustände von 4′‐Hydroxyflavon und 4′‐Methoxyflavon [1]
Authors: Wolfbeis Otto S. , Schipfer Rudolf 
Published: July 2012

AbstractThe absorption and fluorescence spectra of 4′‐hydroxyflavone and 4′‐methoxyflavone have been studied as a function of the acidity (pH or Ho) of the solution. Dissociation constants have been determined for the ground and first excited singlet state. The values are compared with those obtained from Förster‐Weller calculations.—The pKa's obtained by fluorimetry are rather similar to the ground state pKa's, which indicates a rapid deactivation of the S1‐state, before prototropic equilibration is complete.—On changing from protic to deuterated solvents partially strong effects are observed with respect to the fluorescence intensity, but also to the shape of the curves. It is evident, that proton transfer processes in the excited state significantly contribute to fluorescence quenching, thus making the fluorescence quantum yields strongly acidity dependent.
Energetics of Negative Ion Formation in Dissociative Electron Attachment to CCl4, CFCl3, CF2Cl2, and CF3Cl
Authors: Illenberger E. 
Published: July 2012

AbstractNegative ion formation from CCl4, CFCl3, CF2Cl2, and CF3Cl under low energy (0–10 eV) electron impact has been studied mass spectrometrically. Electron affinities of negative ion fragments resulting from dissociative electron attachment are determined by measuring both the appearance potentials and the translational excess energies over the resonances. For the process e− + CF3Cl → Cl− + CF3 the decomposition of the negative ion intermediate CF3Cl−* shows a strong non statistical behaviour which may be explained by the short lifetime of the negative ion state with respect to autodetachment of the extra electron.
Kinetics and Equilibria of Alkali Metal Complexes with Benzo‐Substituted (2,2,2) Cryptands in Propylene Carbonate
Authors: Cox B. G. , Garcia‐Rosas J. , Schneider H. 
Published: July 2012

AbstractStability constants and formation and dissociation rate constants of alkali metal complexes with (2B,2,2) and (2B,2B,2) cryptands in propylene carbonate have been obtained. The incorporation of benzene rings in the ether bridges of the (2,2,2) molecule has the effect of reducing the stability and increasing the dissociation rates of the complexes. The results are compared with previous studies on these and other cryptands in water and methanol. The difference in the stability constants of the complexes on changing the solvent from methanol to propylene carbonate is discussed in terms of the different solvation of the species involved. For a given metal (except for Cs+), it was found that the stability constants of complexes with several cryptands in propylene carbonate can be linearly correlated with the corresponding values in methanol.
The Interaction of Protic Compounds with Thioindigo
Authors: Karstens T. 
Published: July 2012

AbstractBy measuring the temperature dependence of fluorescence intensities and lifetimes a principal difference in the quenching behaviour of thioindigo with aliphatic and aromatic protic compounds is observed. From absorption and IR spectra, an interaction in the groundstate between thioindigo and phenol has to be assumed. Using various substituted phenols the influence of α‐electron density on complex formation is shown.
Diatomics‐in‐Molecules: A Present‐Day Extension of the LEP Formalism
Authors: Kuntz P. J. 
Published: July 2012

AbstractThe relationship of the DIM method to the LEP formalism provides insight into the ways of extending the semi‐empirical description of chemical relations to systems involving complex electronic structures. It is also shown how ab initio ondiatomicmolecules can guide one in choosing an optimum DIM model for a polyatomic system.
Transition State Theory and Beyond — A Constrained Phase Space Approach
Authors: Pollak E. , Levine R. D. 
Published: July 2012

AbstractThe information‐theoretic, maximum entropy formalism for the computation of reaction rates is reviewed, with several applications and computational examples. Attention is focused on the essential ideas and, for simplicity, the analytical development is carried out only for collinear collisions at a given total energy. Particular attention is given to the theories which are of maximal entropy subject to a constraint on the mean number of times n that a critical surface enroute from reagents to products is crossed by the system. Transition state theory is derived as the special case when the mean number of crossings is taken to be unity. The approximation n = 1 is often exact in the threshold region, but as the energy increases it rapidly deteriorates. When n > 1, it is found not to be a dominant constraint. Rather, the nonuniform distribution of trajectories in phase space is the major restriction on the reaction rate. It proves possible to treat this case analytically, and explicit results, illustrated by the H + H2 and F + H2 reactions, are provided.
ESR‐spektroskopische Untersuchungen der Reaktion von O(3P)‐Atomen mit Dichlormonoxid
Authors: Wecker D. , Johanssen R. , Schindler R. N. 
Published: July 2012

AbstractThe kinetics of the reactionmagnified imagewas studied using a fast flow system with ESR‐detection to monitor the O‐atom concentrations. Model calculations were employed to take into account secondary reactions of the intermediates. From investigations in the temperature range 233 to 297 K the room temperature rate constant k1 = (3,1 ± 0,5) · 10−12 cm3 s−1 and an apparent activation energy of EA = (5,8 ± 1,2) kJ/mol−1 were derived.
pVT Data for Fluid Sulphur up to 1200°C and 1000 bar
Authors: Fischer R. , Schmutzler R. W. , Hensel F. 
Published: July 2012

AbstractThe paper presents the first experimental results of the equation of state and its derivatives such as isothermal compressibility, thermal expansion coefficient and thermal pressure coefficient for fluid sulphur which extend over the entire liquid‐vapour range, including the supercritical region up to 1200°C and 1000 bar. Sulphur has a critical point at Tc = 1040°C, pc = 203 bar and pc = 0.58 g/cm3.
Thermodynamic Investigations on Menshutkin Complexes III. Excess Function of Liquid SbCl3/Benzene Mixtures
Authors: Sondern Chr. , Perkampus H.‐H. 
Published: July 2012

AbstractThe excess functions of liquid SbCl3/benzene mixtures have been determined for the temperature range 333 ≦ T/K ≦ 363. For the calorimetric investigation of the heats of mixing a special mixing cell was constructed to be used with a microcalorimeter. The activity coefficients of the components in the mixture were determined by measuring the total equilibrium pressure as a function of temperature and concentration and applying Gibbs‐Duhem's law. All excess functions show negative signs and the same dependence on concentration, thus establishing complex formation between the two components in the liquid state. (HE = ‐ 3.6 kJ mol−1, SE = −7.83 JK−1 mol−1 at xbenzenemax = 0.4).
Electrochemical Determination of Local Hydrogen Concentration in a Metal
Authors: Schoonman J. , Franceschetti D. R. , Hanneken J. W. 
Published: July 2012

AbstractAn electrochemical method for the determination of the local hydrogen activity, and indirectly the local hydrogen concentration, in a metal sample is described. The sample is employed as part of a concentration cell, with the remainder of the cell contained in a movable probe designed so that the electrolyte contacts only a small portion of the sample surface. Two such probes are described, one using an aqueous electrolyte, the other a solid proton conductor. As examples of the method, activity measurements are reported for a palladium wire nonuniformly loaded with hydrogen, and for pressed pellets of Zr powder and crystalline and amorphous samples of intermetallic compounds loaded with hydrogen by both physical and electrochemical means.
Photophysical Processes in Cyanobiphenyl Derivatives. II. Cyanobiphenyl Derivatives as Fluorescent Probes in Micellar Environment
Authors: David C. , Szalaí E. , Baeyens‐Volant D. 
Published: July 2012

AbstractTwo 4‐cyano‐4′‐alkoxybiphenyl derivatives (3 COB‐8 COB) have been used as fluorescent micellar probes in four different surfactants (SDS, CTAB, NPh‐EO‐9, and NPh‐EO‐30) the concentration [S] of which varies in a broad range around the CMC. The distribution constant K for the solubilization of the probes between micelles and water and the solubility S in the surfactant are obtained from the absorption spectra after saturation of the sample either by stirring at room temperature or by ultrasonication. CMC values in agreement with those reported in the literature are determined from the curves λmax = f[S]. According to the saturation method, a different type of aggregate is formed below the CMC in the case of 8 COB. The emission spectra demonstrate that the COB derivatives are preferentially solvated in polar environment (polarity > ethanol). The assignment of the observed enhanced line width as compared to homogeneous solutions reveals the existence of several types of sites with different polarities and indicates inhomogeneous locations in the micelle with exchange times slower than about 1 nanosecond. – The results are tentatively interpreted according to the Fromherz's surfactant‐block model of the micelle.
Über die Phasenumwandlung von Monoschichten des synthetischen Phospholipids DPPA und Vergleich mit DPPC
Authors: Erbrich Uwe , Septinus Manfred , Zimmermann Herbert W. 
Published: July 2012

AbstractThe monolayer phase transition from the liquid‐condensed to the liquid‐expanded phase of the unusual synthetic phospholipid DPPA has been studied with the Langmuir film balance and compared with literature data of DPPC. DPPA and DPPC have different head groups. DPPA has a quarternary acridine orange (AO) residue instead of the quarternary nitrogen atom of DPPC. – The equilibrium pressure π of the phase transition of DPPA increases linearly with the transition temperature Tu: dπ/dTu = 3.1 · 10−5 N cm−1 K−1. The area change ΔFu = 6.6 · 10−16 cm2 per molecule DPPA at the phase transition is within the limits of error independent of π, in contrast to DPPC and other phospholipids. The transition entropy ΔSu = 125 J K−1 mol−1 and transition enthalpy ΔHu = 38 kJ mol−1 are large in comparison to DPPC under equal experimental conditions. The difference is related to the association of the head groups of DPPA in condensed phase. It agrees qualitatively with the thermodynamic parameters of the dissociation of dimers of AO and N‐alkyl AOs.
The Influence of a Miscibility Gap on the Reaction Behaviour of the Quasiternary System HgkCd(1‐k)TelSe(1‐l)
Authors: Leute V. , Schmidtke H. M. , Stratmann W. 
Published: July 2012

AbstractAssuming a regular behaviour of the quasiternary alloy HgkCd(1‐kTelSe(1‐l) we determined the mean molar free enthalpy, the coexistence curve and the spinodal curve. From the concentration profiles taken by an electron microprobe, we calculated the reaction paths for reaction couples of CdTe and HgSe for several reaction times and annealing temperatures. The occurrence of phase separation, precipitations and regions of uphill diffusion is discussed with regard to the influence of the miscibility gap on these phenomena.
63Cu‐, 35Cl‐, and 79,81Br Nuclear Quadrupole Resonance in Copper(II) Complexes with Amino Alcohols
Authors: Okuda Tsutomu , Weiss Alarich 
Published: July 2012

Abstract63Cu‐, 35Cl‐, and 79,81Br nuclear quadrupole resonances were observed in α‐ and β‐bromo(2‐diethylaminoethanolato)copper(II), α(β)‐Cu2Br2(C6H14NO)2, in chloro(2‐diethylaminoethanolato)copper(II), Cu2Cl2(C6H14NO)2, and in chloro(3‐dimethylaminopropanolato)copper(II), Cu2Cl2(C5H12NO)2, at various temperatures. The results are discussed in the frame of the Townes‐Dailey treatment, assuming hybridization of d and p atomic orbitals on Cu. – In the range 160 ≦ T/K ≦ 230 the nuclear quadrupole resonances of 63Cu in α‐Cu2Br2(C6H14NO)2 and in Cu2Cl2(C5H12NO)2 disappear. Also the 35Cl resonance in Cu2Cl2(C6H14NO)2 fades out. The former disappearance is probably due to short spin‐lattice relaxation time T1 and the latter one is caused by a phase transition. A change of signal intensity with temperature was observed for Cu2Cl2(C5H12NO)2.
The Rotation‐Inversion Spectrum of Isocyanamide, H2N — NC, in the Millimeter Wave Region
Authors: Schäfer Eckhard , Winnewisser Manfred 
Published: July 2012

AbstractThe rotation‐inversion spectrum of isocyanamide, H2N — NC, has been investigated in the frequency range 100 to 400 GHz. Due to the near C2v symmetry of the inverting molecule two types of dipole transitions have been observed: 1) intrasystem a‐type transitions and 2) intersystem or rotation‐inversion c‐type transitions connecting the two energy manifolds of H2N — NC belonging to the inversion states O+ and O−, respectively. The inversion splitting was found to be 0.369 cm−1, indicative of a high barrier to inversion. Pure inversion transitions are not allowed. The rotation‐inversion analysis was carried out for 240 a‐type and c‐type transitions using S‐reduced Hamiltonians according to Watson for the O+ and O− inversion states separated by the inversion splitting E1nv. The analysis yielded the following spectroscopic constants:magnified imageplus centrifugal distortion constants. The present data and their analysis provide an excellent basis for a radioastronomical search for H2N — NC.
Influence of the Finite Nuclear Size on the Electronic and Rotational Energy of Diatomic Molecules
Authors: Tiemann E. , Knöckel H. , Schlembach J. 
Published: July 2012

AbstractThe difference of the Coulomb potential for a pointlike and for an extended nucleus is taken as a perturbation of the molecular energy. Correction terms, which are dependent on the mean square nuclear charge radius, are introduced for the molecular energies. The observability of the resulting isotope shift in the molecular spectra is discussed in comparison to the usual mass shift. Some examples for the pure electronic and rotational energy are presented using high precision laser and microwave experiments on Pb‐ and Tl‐compounds.
Photoelektronen‐Spektroskopie an “in situ”‐dargestellten Molekülen
Authors: Bock H. 
Published: July 2012

AbstractPhotoelectron spectroscopy has proven valuable for the analysis and optimization of numerous gas phase reactions in flow‐systems — especially in search for heterogeneous catalysts, which can be tested within a single day using gas mixtures of varying composition over the temperature range from 300 K to 1300 K. In academic research, this real‐time measuring probe allows one to determine — with millimol quantities and within a few hours — the temperatures for different decomposition channels. Simultaneously, main products can be characterized by the comparison of their ionization fingerprints with calculated (SCF) eigenvalue sequences making use of Koopmans theorem. If need be, the yield of a certain reaction product e. g. a short‐lived intermediate can be improved by optimizing the reaction conditions aiming at maximum intensity of the corresponding bands. In this way, many short‐lived and/or reactive molecules such as thioformaldehyde, P2 or silabenzene, which are discussed as examples, have been detected or reaction channels like vinyl azide→2H‐azirineacetonitrile visualized, PE‐spectrometers are well‐suited for on‐line connection to computers; portable instruments for laboratory use are under development.
Laser Multiphoton Ionization of Molecules and Application
Authors: Stuke M. 
Published: July 2012

AbstractExamples for the application of Laser Multiphoton Ionization (MPI) are given. Experimental results on the MPI of gaseous MoF6 and WF6 by an ArF excimer laser show production of Mo2+ and W2+ ions. In the case of WF6 and for an intensity of several GWcm−2, W2+ is the dominating ion.