bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Pressure and Temperature on the Fluorescence Quantum Yield of N-Methylacridone in Solution Interpreted in Terms of the Eyring Transition-StateTheory
Authors: Brauer H.-D. , Schmidt R. , Hammerich B. 
Published: February 2015

Abstract
The influence of temperatur and pressure on the fluorescence quantum yield of N-methylacridone (9,10-dihydro-9-oxo-10-methyl-acridine) in toluene in the range of 283-313 K and 1 bar to 2.5 kbar, respectively, has been investigated. Treatment of the data in terms of the Eyring transition-state theory leads to a consistent interpretation of the observed effect. The unusually large increase of the quantum yield with increasing pressure is attributed to a positive volume of activation, ⊿V≠, for the thermally activated S1-T2 intersystem crossing which is known to be the only deactivation process (of the Si-state) competing with fluorescence. Comparison of the values for ⊿H≠, the activation enthalpy of this process, determined at various pressures, indicates a decrease in ⊿H≠ at elevated pressures. Since ⊿H≠ can be associated with the S1-T2 energy gap involved in intersystem crossing, this result further confirms the conclusion that the change in Franck-Condon factors alone cannot account for the decrease in the intersystem crossing rate with increasing pressure.
T Torque on a Small Particle in a Nonhomogeneous Monatomic Gas
Authors: Vestner H. , Halbritter J. 
Published: February 2015

Abstract
The torque a particle experiences in a monatomic gas in non-equilibrium is calculated with the method Waldmann originally used to compute the force. For a particle which is much smaller than the mean free path in the gas this method involves the following two essential steps:
i) with the help of a boundary condition the torque is expressed by the velocity distribution function of the gas atoms approaching the particle;
ii) this undisturbed distribution function is approximated by a moments-expansion, restricted here to thirteen moments.
In the resulting expression for the torque the pressure tensor and the local vorticity in the gas occur. The geometrical factors are given for particles shaped as spheroids, cylinders and spherocylinders
Birefringence in the Boundary Layer of a Rarefied Heat Conducting Gas
Authors: Oudeman P. , Korving J. , Knaap H. F. P. , Beenakker J. J. M. 
Published: February 2015

Abstract
In a heat conducting gas of diatomic molecules enclosed between parallel plates, the second rank tensor polarization of the rotational angular momenta can be shown to be nonzero in a boundary layer near the plates, a few mean free paths thick. This phenomenon can be experimentally studied by measuring the birefringence of the boundary layer. Although the predicted effects are very small (An of the order of 10-14), the existence of this effect is clearly demonstrated and qualitative results are obtained for N2, CO and HD
A Topological Approach to the Predicting of the Electron Energy Characteristics of Conjugated Infinite Polymers. II. PPP-Calculations
Authors: Bonchev D. , Mekenyan Ov. 
Published: February 2015

Abstract
A topological extrapolation procedure is applied (within the PPP-method) to the predicting of the mean π-electron energy and energy gaps of 10 infinite polymers composed of benzenoid units
A A Tjopological Approach to the Predicting of the Electron Energy Characteristics of Conjugated Infinite Polymers. III. The Influence of Some Structural Modifications of Polymers
Authors: Bonchev D. , Mekenyan Ov. 
Published: February 2015

Abstract
The influence of acyclic conjugated branches on the π-electron energy and energy gaps of infinite polymers containing benzene rings is studied applying a graph-theoretical extrapolation scheme. It is found that methylene branches strongly reduce the energy gap of the unmodified polymers
Correlations between the Ground State and the Triplet State Character Orders of Benzenoid Hydrocarbons
Authors: Bräuchle Chr. , Voitländer J. , Vogler H. 
Published: February 2015

Abstract
The relative localization of the n-conjugation of benzenoid hydrocarbons in the ground state So and the lowest excited triplet state Ti is described by means of character orders. For molecules with the same unmber of electron sextets a linear correlation could be found between the mean character orders of So and Ti indicating the similarities in the electron distribution of these states. The relevance of this similarity for an earlier explanation of the zero-field splitting in Ti is given
Microwave Double Resonance Investigation of Rotational Relaxation of Methyl Iodide-d3
Authors: Schrepp W. , Dreizler H. 
Published: February 2015

Abstract
For a study of rotational relaxation of methyl iodide, CD3I, the method of microwave modulated four-level double resonance has been used. The manifold of the J = 1,2 and 3 levels has been investigated and the η-values have been determined. An experimental procedure to overcome disturbancies produced by the dynamic Stark-effect is described. The sign of the η-values is interpreted in terms of first order dipole and quadrupole type rate constants. The experimental results are in accordance with theoretical results of Rabitz et al. Further a derivation of collisional selection rules for molecules with a nuclear quadrupole moment is given
Thermoreversiblej Photo Valence Isomerization of 9-t-Butylanthracene to its 9,10-Dewar-Isomer
Authors: Dreeskamp H. , Jahn B. , Pabst J. 
Published: February 2015

Abstract
On excitation the first excited singlet state (1La), 9-t-butylanthracene (1) reacts in dilute (10-6-10-3 mole · 1-1) heptane solution with a quantum yield of Φ = 0.016 ± 0.002 to its valence isomer 1-t-butyl-dibenzo-2,5-bicyclo-(2,2,0)-hexadiene (9-t-butyl-9,10-Dewar-anthracene) (2). UV-spectroscopic and 1H-NMR-data of educt and product confirm the proposed isomerization. The reaction is thermoreversible. The first order rate constant of the back reaction was determined in the temperature range of 293 K to 343 K and yielded the activation enthalpy ΔH≠ = 91 ± 3 [kJ · mole-1] and the activation entropie ΔS≠ = - 25 ± 8 [J · mole-1 · K-1] in heptane and 94 ± 3 [kJ · mole-1] and - 17 ± 8 [J · mole-1 · K-1] in ethanole
Experimental and Quantum Mechanical Investigation on Dipole Moments of Some Oxazole Derivatives in Lowest Singlet Excited State
Authors: Gryczyński I. , Jung Ch. , Kawska-Kubicka H. 
Published: February 2015

Abstract
Electric dipole moments in the ground and lowest singlet excited state of four axazole derivatives were calculated theoretically using the PPPCI method, and determined experimentally on the basis of solvatochromic shifts in the electronic spectra
Zur Schwingungsstruktur der Shpolskii-Spektren von Naphthalin in n-Pentan bei 77 K (Fluoreszenz, S0 → S1- und S0 → S2-Absorption) *
Authors: Bałuk P. , Kawski A. , Kałas M. 
Published: February 2015

Abstract
The fluorescence, So -> Si-and So -> S2-absorption spectra of naphthalene in n-pentane at 77 K were measured. The Franck-Condon-Factors are evaluated using equilibrium geometries and normal coordinates of the molecule in the ground (So), in first (Si) and secound (S2) excited singlet states which were calculated by the QCFF/PI-method and by taking the Dushinskii-Efekt into acount. These results were compared with experimentally determined frequencies and estimated relative intensities.
Semiempirical Calculations of Valence Force Constants in C2X4, C3X4 and C4X4 Compounds
Authors: Fleming G. Díaz , Kosmus W. , Kalcher K. 
Published: February 2015

Abstract
e m ie m p iric a l C a lc u la tio n s o f V a le n c e F o rc e C o n s ta n ts in C 2X 4 , C3X4 a n d C 4X 4 C o m p o u n d s Valence force constants were calculated for C2X4, C3X4 and C4X4 (X = H, F, Cl, Br) with a point charge model using CNDO data. The magnitude of the valence force constants is discussed in terms of the polarization of the static electron distribution.
A Heisenberg Ferromagnet With Biquadratic and Dipol-octupol Interactions
Authors: Ba̮k Z. 
Published: February 2015

Abstract
A Heisenberg S - 3/2 ferromagnet with isotropic biquadratic exchange and dipole-octupol coupling is discussed. The conditions for the exact ferromagnetic ground state are derived. The thermodynamical behaviour in the molecular field approximation is discussed. Collective excitation spectra and the 1/z correction to the free energy are found.
Analysis of the Microwave Spectrum of Tricarbon Oxide Sulfide, 0 = C = C = C = S, in Highly Excited Bending States
Authors: Winnewisser Manfred , Peau E. Walter , Yamada Koichi 
Published: February 2015

Abstract
In The microwave spectrum of tricarbon oxide sulphide (3-thioxo-l,2-propadiene-l-one), 0=C= C=C=S, has been measured in the frequency range from 8 to 40 GHz and includes vibrational satellite lines arising from the vibrational manifold of the lowest-lying doubly-degenerate bending mode i>7. The method of analysis followed the theory of rotation-vibrational interaction as devel-oped by Nielsen and Amat. The spectroscopic constants B v and D v as well as several vibration-rotational constants for each vibrational state vy = 0 to 7, = 1 and vq = 1 were determined with the aid of a newly written least squares program. The program structure relies on the cor-relation of the symmetry classification of energy levels in linear and bent molecules, and follows closely the analysis of asymmetric rotor spectra. From the «»vibrational spectrum of C3OS in excited states of vy up to t'7 — 7 and 1 — 6 the sign and magnitude of the effective vibrational anharmonicity constant xi t i t were determined. The interpretation of these results yields the infor-mation that in C3OS the potential function describing the two-dimensional oscillator of the vj bending mode is very harmonic and does not contain a perturbing hump. The dynamic behaviour of C3OS, a classical example of a linear molecule, is thus in sharp contrast to the quasilinear be-haviour of C3O2 •
Schwingungsspektren der Tetraphosphortetrasulfide
Authors: Bues W. , Somer M. , Brockner W. 
Published: February 2015

Abstract
The solid-state i.r. and Raman spectra of the crystalline tetraphosphorus tetrasulphides -α -P4S4 and β-P4S4 - and the Raman spectrum of the α-P4S4 melt have been recorded. The observed frequencies of α-P4S4 were tentatively assigned to P4S4 molecules of the cradle type, possessing D2d symmetry. An assignment of the β-P4S4 frequencies to a cage-like P4S4 unit with Cs symmetry is proposed and based on comparison with similar P-S-compounds such as P4S3 and α-P4S5. All the tetraphosphorus tetrasulphides decompose during melting into P4S3, P4S7 and β-P4S6.
Schwingungsberechnungen der käfigstrukturierten Moleküle P4Se3 , AS4S3, As4Se3 und PAs3S3 / Molecular Vibration Analysis of the cage-like Molecules P4Pe3, As4S3, As4Se3 and PAs3S3
Authors: Brockner W. , Somer M. , Cyvin B. N. , Cyvin S. J. 
Published: February 2015

Abstractn
The P4Se3, As4S3, As4Se3 and PAs3S3 molecules are supposed to have a cage-structure of the C3V symmetry. Normal coordinate analyses for these molecules were performed, based on a very simple initial force field transferred from P4S3. The force field was refined by adjusting the symmetry force constants to fit exactly observed frequencies. The force fields were used to calculate the mean amplitudes of vibration and Coriolis coupling constants. The standard thermodynamical functions from spectroscopic data are also given.
Photocatalytic Splitting of Liquid Water by n-TiO2 Suspension
Authors: Vonach Waltraud , Getoff Nikola 
Published: February 2015

Abstract
By illumination (λ>300 nm) of a suspension of n-TiO2 (grain size ≦0.06 mm, 3 to 15 mg/ml) in aqueous acid solutions, containing 10-3 mol · dm-3 Ce4+ -ions an enhanced evolution of oxygen is observed. Its yield is dependent on the amount of TiO2 in the suspension and on the temperature. Using n-TiO2 suspended in diluted sulfuric acid, hydrogen and oxygen were produced in a ratio of about 2: 1. In both systems n-TiO2 is acting as an efficient electron donor. For the explanation of the processes probable reaction mechanisms are proposed.
Dipole Moments and Polarizabilities of Benzophenones Estimated from Spectroscopic Measurements
Authors: Stori M. 
Published: February 2015

Abstract
The effect of microenvironment on the absorption spectra of benzophenone and its aminoderivatives in n-heptane/n-butanol and n-heptane/benzene mixtures was investigated. The local dielectic constants, the composition of the solvatation shell, the Onsager cavity radius "a" and the values of a/a3 (α - the polarizability of solute molecules) have been evaluated from the spectral shifts.
On the Order-Disorder Phase Transformation of Anilinium Halides.
Authors: Fecher Gerhard , Weiss Alarich , Heger Gernot 
Published: February 2015

Abstract
The crystal structure of the low temperature phase of anilinium bromide, C6H5NH3
⊕Br⊖, was studied by neutron diffraction at T = 100 K. The refinement supports an ordered structure. The structures of the low and high temperature phases are compared and the mechanism of the phase transformation is discussed.
Influence of Environment on the Electronic Spectra of Donor-Acceptor-Substituted trans-Stilbenes in Solvent Mixtures
Authors: Kawski A. , Ostrowska B. , Ston M. 
Published: February 2015

Abstract
The effect of n-heptane and n-butanol mixtures upon the absorption and fluorescence spectra of donor-acceptor-substituted trans-stilbenes is investigated. The electronic-vibration spectra of these compounds depend upon the magnitude of the electric dipole moments in the ground and excited states, upon the relation between the mean lifetime τf
w and the time of dielectric relaxation τR, and upon the environment around the solute molecule.
Ultrasonic Studies in N-(p-n-butoxybenzylidene)-p-n-butylaniline
Authors: Rao J. V. , Murty C. R. K. 
Published: February 2015

Abstract
The ultrasonic velocity in the SG(SH), SB, SA, Nc , N0 and isotropic liquid phases of N-(p-n-butoxybenzylidene)-p-n-butylaniline (BBBA) has been measured as a function of temperature. A transition in the nematic phase seems to indicate the existence of an ordinary nematic and a cybotactic nematic phase. The transition SG-SB has been found for the first time with the ultra-sonic velocity method. The adiabatic compressibility βad and the molar sound velocity Rn (Rao number) have been determined using the experimental density and ultrasonic velocity.
Thermische Oszillationen und chaotisches Verhalten bei der Oxidation von Kohlenmonoxid an Pd-Kristalliten im Inneren einer Zeolithmatrix / Thermal Oscillations and Chaotic Behaviour at the Oxidation of CO on Pd Crystallites within a Zeolite Matrix
Authors: Jaeger N. I. , Möller K. , Plath P. J. 
Published: February 2015

Abstract
The oxidation of CO on a Pd supported catalyst was investigated in a differential reactor. The catalyst consisted of a homogeneous distribution of Pd crystallites (∅ =8 - 10 nm) within a zeolite matrix (Faujasite type X). Depending on the temperature of the reactor and the CO con-centration in the feed gas bistable, periodic and chaotic behaviour of the temperature of the catalyst bed could be observed.
Activity Coefficients and Excess Molar Gibbs Functions of Liquid Alkali Halide + Silver Halide Mixtures at Varying Temperature and Composition
Authors: Richter J. , Conradt R. , Becker R. 
Published: February 2015

In certain temperature ranges, the e.m.f. of binary molten salt concentration cells without transference can be described by a mole fraction expansion with three constants depending linearly on temperature.
With the six constants it is possible to calculate the activity coefficients, the thermodynamic factor, and the excess molar Gibbs function of liquid alkali halide + silver halide mixtures at given temperatures and compositions. The precision of the representation corresponds to an accuracy in the e.m.f. data of 0.5 mV to 1.2 mV.
Iteration-Perturbation Theory of Covalent Bonding in Crystals
Authors: Krasko Genrich L. 
Published: February 2015

An iteration-perturbation approach is suggested which enables the calculation of the binding energy and equilibrium lattice parameters of non-metallic crystals. Making use of the single­band-gap model, the selfconsistent Schrödinger equation can be solved in terms of the effective matrix elements, W(g)′s, which, in general, satisfy the set of nonlinear equations. The latter are solved for those reciprocal lattice vectors g for which the perturbation theory requirements are violated. Since the matrix elements of ion-electron interaction are not small for some g’s the screening of all the interactions in the crystal is not linear. The exchange-correlation contributions both in the screening and in the total energy are accounted for by means of the Kohn-Sham density-functional-formalism. A charge transfer is shown to result in excluding part of the electrons from the screening processes. The theory allows also for the possibility of a strongly non-homogeneous electron density distribution in the crystal.
The results of the calculation for magnesium hydride MgH2 are presented in paper II.
Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations
Authors: Palmer Michael H. , Simpson Isobel , Wheeler J. Ross 
Published: February 2015

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.
Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.
Application of Multichannel Scattering Theory to Pionic Reactions Within the Lee Model
Authors: Sawicki M. , Schütte D. 
Published: February 2015

Abstract
The multichannel scattering theory is applied to the (2,2) sector of the (non-static) Lee model. Rigorous expressions for the transition amplitudes for two-fragments channels are derived. These expressions contain all effects of off-shell renormalization in a complete and consistent way. With suitable identification of the elementary fields of the model the reactions considered correspond to a simplified description of elastic proton-proton and pion-deuteron scattering and to pion absorption on the deuteron. We obtain a two-body equation for the description of the elastic proton-proton scattering and an extension of the two-potential formula for the pion-deuteron scattering, which can be cast into the form of the multiple-scattering series.
Internal Rotation Spectrum in the Ground State of cis Propionyl Fluoride
Authors: Scappini F. , Dreizler H. 
Published: February 2015

Abstract
The microwave ground state spectrum of cis propionyl fluoride has been investigated expanding, with respect to a previous study, the range of the quantum numbers of the transitions, J up to 40 and K up to 18. At low K the spectrum resembles that of an asymmetric rigid rotor, except in a number of cases where the lines are split into A, E doublets. At intermediate and high K the mixing of the if-doublet rigid rotor wave functions makes forbidden transitions appear. The results of the analysis of the methyl top internal rotation ground state splittings are: V3 = 2350 ± 11 cal/mole, ≮ (i, a) = 32.7° ±2.0°, and Iα = 3.18 ± 0.03 uÅ2.
Structure of the Benzene-Argon Complex in the Gas Phase at 3 Kelvin
Authors: Fung K. H. , Selzle H. L. , Schlag E. W. 
Published: February 2015

Abstract
The structure of the benzene-argon complex is determined from a high resolution band contour of the ν6 transition of the complex measured in a hypersonic jet. It is shown that the argon is located on the main symmetry axis of the benzene molecule. The distance from the center of the benzene ring is found to be 3.4 Å.
Wavelengths of the M X-Ray Spectra of Uranium, Neptunium, Plutonium, and Americium
Authors: Kleykamp H. 
Published: February 2015

Abstract
The M series of the X-ray spectra of uranium, neptunium, plutonium, and americium have been measured between 250 and 520 pm by means of a linear spectrometer. The relative intensities of the lines have been normalized to the respective Mα1 lines of the actinides.
Investigation of the Nitrogen Hyperfine Structure of Vinylisocyanide by Microwave Fourier Transform Spectroscopy in the X-and Ku-Band
Authors: Bestmann G. , Dreizler H. 
Published: February 2015

Abstract
In memory of W. H. We discuss the features of a microwave Fourier transform spectrometer in the X-and Ku-band as applied to the investigation of the hyperfine structure of rotational transitions. The Nitrogen-hyperfine structure of vinylisocyanide was measured and analysed.
The Concentrational Changes of the Fluorescence Decay Time of Rhodamine B in Ethanol
Authors: Bojarski C. , Żurkowska G. , Tyrzyk J. 
Published: February 2015

Abstract
The photoluminescence decay time τ of neutral solutions of rhodamine B in ethanol was mea-sured for concentrations c from 10-5 mol 1-1 to 10-2 mol 1-1 at 295 K. The τ(C) curve observed is atypical, showing two regions of decreasing r. The drop over the range 4 X 10-4 to 10-3 mol 1-1 was explained by the presence of two ionic forms of rhodamine B, and that at concentrations greater than 4 X 10-3 mol 1-1 - by rhodamine B dimers.
Decay Instability of an Electromagnetic Wave Incident on a Weakly-Inhomogeneous Magnetised Plasma
Authors: Shivamoggi Bhimsen K. 
Published: February 2015

Abstract
This paper considers the parametric decay of an electromagnetic wave incident on a weakly-inhomogeneous magnetised plasma into a Langmuir wave and an ion-acoustic wave. The Vlasov model is used in order to calculate the low-frequency electron-density perturbation produced by the beating of the side-band modes with the pump wave. The results show that the threshold value of the pump wave to undergo a decay instability drops in the presence of an inhomogeneity in the plasma.
Nuclear Quadrupole Perturbations in 51V NMR Spectra of Oxovanadium(+V) Complexes
Authors: Paulsen Kurt , Rehder Dieter 
Published: February 2015

Abstract
Nuclear electric quadrupole coupling constants e2qQ/h have been obtained by evaluation of quadrupole perturbations in 51V NMR spectra of various vanadyl esters and esterchlorides of the general formula VOCl3-n(OR)n (n=0-3; R = Me, Prn , Prn, Bun and Bui). e2qQ/h values have been calculated from (i) 2nd. order quadrupole splittings of the 51V NMR signals in pseudo-polycrastalline samples, (ii) 1st. order quadrupole splittings in nematic liquid crystals and (iii) line widths A ⊿ν1/2 of the 51V and 35Cl NMR signals in the liquid isotropic state and e2qQ/h(35Cl) obtained by pure NQR measurements. The influences of the asymmetry parameter η and the orientation of the crystallites in powder spectra are considered, and temperature and concentration effects upon ⊿ν1/2 and 51V shielding (isotropic phases) and the ordering factor Sa (meso-phases) are discussed.
X-ray Diffraction Study of the Coordination of Fe(III) in a Highly Hydrolyzed Solution of Iron(III) Chloride
Authors: Piccaluga G. 
Published: February 2015

Abstract
A highly hydrolyzed solution of iron(III) chloride is investigated by X-ray diffraction. The occurrence of six O atoms in the first coordination shell of iron(III) is demonstrated. The structural similarity of hydrolyzed solutions of Fe(III) chloride and nitrate is pointed out.
63 Cu NMR Studies of Copper (I) Complexes in Solution: Influence of Anion, Solvent and Temperature on the Linewidth and Chemical Shift of the Copper Resonance
Authors: Kroneck Peter , Kodweiß Jürgen , Lutz Otto , Nolle Alfons , Zepf Daniela 
Published: February 2015

Abstract
The behaviour of the 63Cu nuclear magnetic resonance signals in tetrahedrally coordinated copper(I) complexes has been investigated as a function of temperature, solvent and anion. From the strong dependence of the linewidth and the chemical shift on these parameters, exchange processes with complexes of lower symmetry are concluded.