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Volume 40 Issue 6

Issue of Zeitschrift für Naturforschung A

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Open Access June 2, 2014

Thiophosphonyl Radicals Photolytic Generation and Reactivity Towards Olefinic Compounds

T. Sumiyoshi, W. Weber, W. Schnabel

Page range: 541-543

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Abstract

Upon irradiation with UV light (λ = 347 nm), 2,4,6-trimethylbenzoyldiphenylphosphine sulfide was found to be fragmented into free radicals by α-scission (F(k) = 0.3 ± 0.1): Flash photolysis studies revealed that the optical absorption spectrum of diphenylthiophosphonyl radicals, S = P(Ph) 2 . possesses a strong band with λ max = 340 nm and a somewhat weaker band with λ max ≈ 500 nm (e 340nm = 1.2 ± 0.2) · 10 4 1/mol cm). The reactivity towards olefinic compounds, M, is 10 to 30 times lower than in the case of O = P(Ph) 2 radicals. Typical bimolecular rate constants (in 1/mol s) of the reaction of S = P(Ph) 2 with M are: 4 x 10 6 (styrene), 6.2 x 10 5 (methylacrylate), 4.2 x 10 4 (vinyl acetate).

Open Access June 2, 2014

Glass Forming Ability of GeTeSn with Tin Concentration and Initial Conditions

B. Arcondo, G. Quintana, H. Sirkin

Page range: 544-547

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Abstract

Solid samples of (Ge 15 Te 85 ) l-k Sn k and (Sn k Ge l−k ) 15 Te 85 ternary alloys with different tin concentrations were obtained from the liquid state at different initial temperatures (T 0 ) by the splat cooling technique. They were analized by X-ray diffraction and Mössbauer spectroscopy. The results were compared with results obtained in similar studies on slowly cooled and annealed samples. The previous observation that increasing tin concentration renders the formation of the amorphous phase more difficult, is confirmed. For a fixed k, and T 0 < 800 °C, the higher T 0 the easier the glassy phase is obtained. This behaviour reverses for T 0 > 800 °C.

Open Access June 2, 2014

Mössbauer and X-Ray Studies on Splat Cooled SnGeCu Alloy

H. Sirkin, B. Arcondo, E. Duhalde, E. Nassif, G. Quintana

Page range: 548-550

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Abstract

Solid samples of (Sn k Ge 1− k ) 36 Cu 64 with different tin concentrations were produced by the Splat Cooling technique. The melted material was cooled down from different initial temperatures (T 0 ). These samples were analyzed by Mössbauer spectroscopy and X-ray diffraction. The results are compared with those obtained in similar measurements on the annealed samples and on the slowly cooled material. The fast quenched samples were all polycrystallines. The resultant phases are analized and a memory effect of the liquid state in the solid material is discussed.

Open Access June 2, 2014

Evaluation of Partial Structure Factors in the Small Q-Region with Amorphous Ni₈₀P₂₀ by Neutron Diffraction Using Isotopic Substitution

K. Schild, F. Frisius, P. Lamparter, S. Steeb

Page range: 551-558

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Abstract

Amorphous Ni 80 P 20 -alloys were produced under He-atmosphere by the melt spin technique. With three specimens produced from P with nat Ni, 62 Ni and 0 Ni elastic scattering expriments were performed using neutrons with l = 5.4 Å in the Q-region 6 · 10 −3 Å −1 ≦ Q ≦ 2.7 · 10 −1 Å −1 . The measured intensities were corrected for absorption and background, desmeared, and normalized. The partial Bhatia Thornton structure factors S NN , S CC , and S NC w e r e evaluated and allowed the following conclusions: The a-Ni 80 P 20 -alloy contains regions with radii of about 6.5 Å caused by concentration fluctuations. A method is presented which allows to determine the composition of the regions and the total content of regions within the specimen. In the small Q-region (6 · 10 −3 Å −1 ≦ Q ≦ 4 · 10 −2 Å −1 ) the run of the partial structure factors is proportional to Q −3 caused by concentration- and density-fluctuations. From the partial Fourier transforms follows a slight anisotropy concerning the chemical arrangement with correlation lengths elongated along the ribbon direction.

Open Access June 2, 2014

Temperature Dependence of Limiting Fluorescence Anisotropy of POPOP in Cellulose Acetate Film

A. Kawski, A. Kubicki, I. Weyna, I. Janić

Page range: 559-561

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Abstract

The effect of temperature (103 K < T < 303 K) upon the limiting fluorescence anisotropy r 0 of POPOP was investigated in a cellulose acetate film. A slow increase in r 0 was observed when reducing the temperature. Based on the Jabłoński theory, the frequency of the torsional vibrations of POPOP was determined to be w = 1.3 x 10 12 s −1 . The depolarization due to these torsional vibrations was found to occur immediately following excitation during the thermal relaxation of the luminescent centre, thus somewhat lowering the value of the fundamental fluorescence anisotropy r f to the limiting r 0 value.

Open Access June 2, 2014

Hyperchaos in the Post-Breakdown Regime of p-Germanium

J. Peinke, B. Röhricht, A. Mühlbach, J. Parisi, Ch. Nöldeke, R. P. Huebener, O. E. Rössler

Page range: 562-566

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Abstract

p-Ge electrically driven into the post-breakdown regime at liquid-He temperatures produces voltage oscillations which can be attributed to the formation of a chaotic attractor. Under variation of an applied magnetic field, a change in this attractor takes place which apparently reflects an increase in attractor dimensionality. A sequence of phase plots is presented which is interpreted as a transition from ordinary chaos to hyperchaos.

Open Access June 2, 2014

Pyroelectricity of Molecular Crystals: Benzene Derivatives

Tetsuo Asaji, Alarich Weiss

Page range: 567-574

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Abstract

The pyroelectric coefficient at constant stress was measured for meta-nitroaniline, meta-amino-phenol, and 2,3-dichlorophenol in the temperature range 90 Ù T/ K ⪅ % melting point. A change in sign of the pyroelectric coefficient was observed in meta-nitroaniline and 2,3-dichlorophenol. At room temperature p 3 s is 9 m Cm −2 K −1 for meta-nitroaniline, 42 m Cm −2 K −1 for meta-aminophenol, and 0.3 m Cm −2 K −1 for 2,3-dichlorophenol (at 263 K for the latter one). By a classical harmonic oscillator model the contribution to the pyroelectric coefficient due to molecular dipole librational motions was estimated to be fairly small for meta-nitroaniline. The temperature dependence of the coefficient of meta-nitroaniline is discussed on the basis of Boguslawski's theory. The importance of internal polar optical modes for the temperature dependence of the pyroelectric coefficient of molecular crystals is shown.

Open Access June 2, 2014

Determination of a High Potential Barrier Hindering Internal Rotation from the Ground State Spectrum. The Methylbarrier of Ethylbromide

J. Gripp, H. Dreizler, R. Schwarz

Page range: 575-587

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Abstract

For ethylbromide a determination of the parameters of internal rotation is given derived from the rotational spectrum of the torsional and vibrational ground state. The Br-hyperfine structure is reanalysed with higher precision. As high J transitions were measured a centrifugal distortion analysis was necessary.

Open Access June 2, 2014

Dielectric Relaxation in Binary and Ternary Mixtures of Ethanol, Water, and Benzene or n-Hexane

H. Utzel, M. Stockhausen

Page range: 588-595

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Abstract

The complex permittivity of the partially miscible systems ethanol-water-benzene and ethanol-water- n-hexane has been measured in the frequency range from 20 MHz to 36 GHz at 20 °C. The results are described as superposition of Debye-terms, which are considered as physically significant and are ascribed to (i) higher, ill-defined, fluctuating self- and hetero-associates (main term), (ii) associates of lower order, relaxing by rotational tumbling, (iii) free molecules. The demultimerization by benzene appears to be more effective than by hexane.

Open Access June 2, 2014

CH₃ Rotational Tunnelling in Alkali Acetates and Correlation between NMR Spin-Lattice Relaxation and Neutron Scattering Data

A.-S. Montjoie, W. Miiller-Warmuth

Page range: 596-601

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Abstract

NMR spin-lattice relaxation rates l / T 1 have been measured at 15 and 30 MHz and various temperatures in polycristalline sodium and potassium acetate. The results for CH 3 COONa are characteristic of methyl group tunnelling with a frequency which is very much larger than the NMR Larmor frequency. Derived values of the torsion energy (1.1 kJ/mol) and the ground state tunnel splitting (5.6 meV) agree with data obtained from inelastic neutron scattering by Clough et al. The shape of the hindering potential and the activation energy for classical reorientation (3.2 kJ/mol) have been determined. Since the relaxation rate of CH 3 COOK is a superposition of at least two mechanisms, in this case the results are less accurate and refer to one type of CH 3 rotor only: activation energy 5.4 kJ/mol, tunnel splitting 0.23 meV. Comparison is made between tunnel splittings and classical activation energies for the acetates and various other materials: strong correlations are demonstrated and discussed.

Open Access June 2, 2014

Interrelation between Molecular Motions and Phase Transitions in Monomethylammonium Perchlorate. A Study by DSC, Proton, and Deuteron NMR

S. Jurga, H. W. Spiess

Page range: 602-610

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Abstract

Differential scanning calorimetry, the temperature dependence of proton and deuteron lineshapes and spin-lattice relaxation times are reported for the isotopic species CH 3 NH 3 ClO 4 , CD 3 NH 3 ClO 4 and CH 3 ND 3 ClO 4 of monomethylammonium Perchlorate. The data confirmed the existence of three different phase modifications in monomethylammonium Perchlorate and its selectively deuterated analogues. In addition they were used to identify the molecular motions occurring in the respective phases and to determine their activation parameters. In the low temperature phase III, stable below 320 K. the CH 3 and NH 3 groups reorient about their threefold symmetry axes C 3 with different frequencies. In the low-temperature range of this phase the deuteron quadrupole coupling constant indicates N - H ... O hydrogen bonds between the monomethylammonium and the Perchlorate ions. In the intermediate phase II, between 320 K and 451 K for CH 3 NH 3 ClO 4 and CD 3 NH 3 ClO 4 and 320 K and 437 K for CH 3 ND 3 ClO 4 , the methylammonium ions reorient about an axis inclined at an angle of 18 degrees to the C 3 axis. The analysis of the entropy changes, associated with the III- II transitions indicates that the ClO 4 − ions have a large motional freedom in phase II, presumably because of breaking or weakening of N - H . . . O hydrogen bonds. In phase I the monomethylammonium ions undergo isotropic motion along with translational diffusion between different sites of the primitive cubic unit cell.

Open Access June 2, 2014

A Reactive System with Diffusive Transport Displaying Two Different Symmetry-Breaking Dissipative Structures

Ariel Fernández, Oktay Sinanoğlu

Page range: 611-618

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Abstract

An open reactive system is modelled by coupling the chemical kinetics to diffuse transport. This system operates far from the regime of linear irreversible thermodynamics. The kinetics correspond to a certain region in the parameter space of the Oregonator for which two symmetrybreakdowns occur: a) A periodic orbit contained in an unstable manifold of the phase space. This solution is invariant under time-translations generated by a period. b) A spatial stationary dissipative structure. This solution is invariant under a subgroup of the space symmetry group. The initial time periodicity of the system is followed by a spatial pattern. The restriction to the center manifold in the phase space allows to reduce an infinitedimensional problem for the bifurcation of a semiflow to a finite dimensional system of ordinary differential equations. The ranges in the control concentrations for this dynamics is found in accord with the experimental values. We also demonstrate that if the vessel is stirred after the Turing pattern has emerged, the freezed wave is destroyed and the time-periodic behavior is achieved again.

Open Access June 2, 2014

Konformationsuntersuchungen an Tetrahydroisochinolin- und Tetrahydronaphthalin-Semichinonen durch ESR-Spektroskopie

Klaus Scheffler, Klaus Stolze, Hartmut B. Stegmann

Page range: 619-626

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Abstract

Semiquinones of 6,7-dihydroxy- 1,2,3,4-tetrahydroisoquinolines and -naphthalenes are investigated by ESR-spectroscopy in the presence of diorganothalliumhydroxide. The ESR-spectra show a significant temperature dependence of the coupling constants of the β-methylene protons due to ring inversion of the partially hydrogenated ring. Computer simulation of the spectra gave the rate constants and the activation parameters for this ring inversion process. The heterocyclic compounds show considerably lower rate constants due to implication of N-inversion. In comparison to analogous cyclohexene-semidione systems, our systems showed rate constants about 10 times higher than those of their monocyclic counterparts.

Open Access June 2, 2014

Megahertz Dielectric Relaxation in the Nematic Phases of 4,4′-di-n-propyloxyazoxybenzene and 4,4′-di-n-pentyloxyazoxybenzene

Nguyen X. Phuc, W. Otowski, J. Chruściel, H. Kresse, S. Urban, S. Wróbel

Page range: 627-631

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Abstract

The dielectric properties of the third (3. OAOB) and fifth (5. OAOB) members of the PAA homologous series have been investigated in the frequency range from 0.1 to 12 MHz. Negative dielectric anisotropies have been obtained in the nematic phase of both substances. For the dielectric relaxation processes observed parallel to the nematic director, the relaxation times and activation energies have been estimated and discussed.

Open Access June 2, 2014

Effect of Pressure on Strongly Polar Liquid Crystals

S. Krishna Prasad, S. Pfeiffer, G. Heppke, R. Shashidhar

Page range: 632-635

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Abstract

The effect of pressure on several mesogens which possess a strongly polar terminal group (CN or NO 2 ) is studied. In all cases the partially bilayer smectic A (A d ) gets bounded while the nematic phase gets more stabilised at high pressures. In the case of reentrant nematogens, the maximum pressure of smectic stability is seen to be related to the temperature range of the nematic phase at 1 bar.

Open Access June 2, 2014

On Topology-Property Relations of Polycyclic Aromatic Hydrocarbons

M. Zander

Page range: 636-638

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Abstract

The hydrogen-depleted graphs of polycyclic aromatic hydrocarbons contain two types of vertices (with regard to their degree) and correspondingly three types of edges. The respective sums of these edges reflect the molecular topology of the hydrocarbons and were used for constructing a new topological index for kata-annellated aromatic hydrocarbons that correlates well with their topological resonance energies per electron. Dependent on the degrees of their first neighbours, the vertices of degree 2 of polycyclic hydrocarbons can be distinguished as to high, medium and low chemical reactivity of the corresponding carbon atoms, in agreement with the results from MO theory and experiments.

Open Access June 2, 2014

Coriolis Coupling Constants and Inertia Defect of Urea

M. Campos-Vallette, C. A. Acevedo-Gonzalez, G. Diaz F., R. Peña C.

Page range: 639-643

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Abstract

Coriolis coupling constants and the inertia defect for urea have been calculated using force constants obtained by the iterative consistency method. The Coriolis coupling constants are very sensitive to the force constant variation and the value of the inertia defect is calculated to be 0.0119 umaÅ 2 .

Open Access June 2, 2014

An Intermolecular Potential Function for Cyclen-Water Derived from Ab-Initio Molecular Orbital Calculations

Supot V. Hannongbua, Bernd M. Rode

Page range: 644-648

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Abstract

An interaction pair potential function for 1,4,7,10-tetraaza-cyclododecane (cyclen) and water has been derived from ab-initio molecular orbital computations. The 250 computed points of the energy surface for the water-cyclen interaction have been fitted with an analytical potential of the form where A, B. C, and D are constants, and q i , and q j are the atomic charges of the i-th atom of water and the j-th atom of cyclen at infinite separation.

Open Access June 2, 2014

Notizen: A Note on the Stratified Turbulent Flow with no Shear

A. K. Chakraborty, H. P. Mazumdar

Page range: 649-650

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Open Access June 2, 2014

Notizen: Elementary Derivation of the Dirac Equation. IX

Hans Sallhofer

Page range: 651-652

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About this journal

Objective
A Journal of Physical Sciences: Zeitschrift für Naturforschung A (ZNA) is an international scientific journal which publishes original research papers from all areas of experimental and theoretical physics. Authors are encouraged to pay particular attention to a clear exposition of their respective subject, addressing a wide readership. In accordance with the name of our journal, which means “Journal for Natural Sciences”, manuscripts submitted to ZNA should have a tangible connection to actual physical phenomena. In particular, we welcome experiment-oriented contributions.

Manuscripts considered for publication in A Journal of Physical Sciences: Zeitschrift für Naturforschung A undergo high-level refereeing. Mere formal correctness of a paper is not sufficient for its acceptance. Moreover, articles reporting a merely marginal extension of already existing knowledge are considered unsatisfactory. Instead, the key quality a publication in A Journal of Physical Sciences: Zeitschrift für Naturforschung A should possess is that it makes a genuine contribution to the advancement of its topic.

Topics

Atomic, Molecular & Chemical Physics
Dynamical Systems & Nonlinear Phenomena
Gravitation & Cosmology
Hydrodynamics
Quantum Theory
Solid State Physics & Materials Science
Thermodynamics & Statistical Physics

Article formats
Original research articles, research notes, letters and review articles from all areas of theoretical and experimental physics

Information on submission process

Volume 40 Issue 6

Issue of Zeitschrift für Naturforschung A

Thiophosphonyl Radicals Photolytic Generation and Reactivity Towards Olefinic Compounds

Abstract

Glass Forming Ability of GeTeSn with Tin Concentration and Initial Conditions

Abstract

Mössbauer and X-Ray Studies on Splat Cooled SnGeCu Alloy

Abstract

Evaluation of Partial Structure Factors in the Small Q-Region with Amorphous Ni80P20 by Neutron Diffraction Using Isotopic Substitution

Abstract

Temperature Dependence of Limiting Fluorescence Anisotropy of POPOP in Cellulose Acetate Film

Abstract

Hyperchaos in the Post-Breakdown Regime of p-Germanium

Abstract

Pyroelectricity of Molecular Crystals: Benzene Derivatives

Abstract

Determination of a High Potential Barrier Hindering Internal Rotation from the Ground State Spectrum. The Methylbarrier of Ethylbromide

Abstract

Dielectric Relaxation in Binary and Ternary Mixtures of Ethanol, Water, and Benzene or n-Hexane

Abstract

CH3 Rotational Tunnelling in Alkali Acetates and Correlation between NMR Spin-Lattice Relaxation and Neutron Scattering Data

Abstract

Interrelation between Molecular Motions and Phase Transitions in Monomethylammonium Perchlorate. A Study by DSC, Proton, and Deuteron NMR

Abstract

A Reactive System with Diffusive Transport Displaying Two Different Symmetry-Breaking Dissipative Structures

Abstract

Konformationsuntersuchungen an Tetrahydroisochinolin- und Tetrahydronaphthalin-Semichinonen durch ESR-Spektroskopie

Abstract

Megahertz Dielectric Relaxation in the Nematic Phases of 4,4′-di-n-propyloxyazoxybenzene and 4,4′-di-n-pentyloxyazoxybenzene

Abstract

Effect of Pressure on Strongly Polar Liquid Crystals

Abstract

On Topology-Property Relations of Polycyclic Aromatic Hydrocarbons

Abstract

Coriolis Coupling Constants and Inertia Defect of Urea

Abstract

An Intermolecular Potential Function for Cyclen-Water Derived from Ab-Initio Molecular Orbital Calculations

Abstract

Notizen: A Note on the Stratified Turbulent Flow with no Shear

Notizen: Elementary Derivation of the Dirac Equation. IX

Evaluation of Partial Structure Factors in the Small Q-Region with Amorphous Ni₈₀P₂₀ by Neutron Diffraction Using Isotopic Substitution

CH₃ Rotational Tunnelling in Alkali Acetates and Correlation between NMR Spin-Lattice Relaxation and Neutron Scattering Data