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Volume 35 Issue 8

Issue of Zeitschrift für Naturforschung A

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Open Access June 2, 2014

Origin of Iron Meteorite Groups IAB and IIICD

John T. Wasson, John Willis, Chien M. Wai, Alfred Kracher

Page range: 781-795

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Abstract

Several low-Ni iron meteorites previously assigned to group IAB are reclassified IIICD on the basis of lower Ge, Ga, W and Ir concentrations and higher As concentrations; the low-Ni extreme of IIICD is now 62 mg/g, that of IAB is 64 mg/g. The resulting fractionation patterns in the two groups are quite similar. It has long been established that, in contrast to the magmatic iron meteorite groups, IAB and IIICD did not form by fractional crystallization of a metallic magma. Other models have been proposed, but all have serious flaws. A new model is proposed involving the formation of each iron in small pools of impact melt on a parent body consisting of material similar to the chondritic inclusions found in some IAB and IIICD irons, but initially unequilibrated. These impact melts ranged in temperatures from ~ 1190 K to ~ 1350 K. The degree of equilibration between melt and unmelted solids ranged from minimal at the lowest temperature to moderate at the highest temperature. The lowest temperature melts were near the cotectic in the Fe-Ni-S system with Ni contents of ~ 12 atom %. Upon cooling, these precipitated metal having ~ 600 mg/g Ni by equilibrium crystallization. The Ni-rich melt resulted from the melting of Ni-rich sulfides and metal in the unequilibrated chondritic parent. Low-Ni irons formed in high temperature melts near the composition of the FeS-Fe eutectic or somewhat more metal rich. We suggest that the decreasing Ge, Ga and refractory abundances with increasing Ni concentration reflect the trapping of these elements in oxide phases in the unequilibrated chondritic material, and that very little entered the Ni-rich melt parental to the Oktibbeha County iron. The remaining elements tended to have element/Ni ratios in the melts that were more or less independent of temperature. The remarkable correlation between I-Xe age of the chondritic inclusions and Ni content of the host metal is explained by a detailed evolution of (mega)regolith in which these groups originated. The most Ni-rich melts could only be generated from an unequilibrated chondrite parent; as the continuing deposition of impact energy produced increasingly higher grades of metamorphism, the maximum Ni content of the impact melts (and their subsequently precipitated metal) gradually decreased.

Open Access June 2, 2014

Unification of Brueckner Theory and HFB Theory

Y. Gerstenmaier, D. Schütte

Page range: 796-807

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Abstract

A cluster expansion for the expectation value of operators with correlated wave functions is presented. A variational approach to the Brueckner theory with occupation probabilities is generalized and HFB theory incorporated.

Open Access June 2, 2014

Absolutmessung der kontinuierlichen Strahlung des Heliums im Lichtbogen von λ = 109 bis 540 nm / Measurement of the Helium Continuum Radiation from λ = 109 to 540 nm in an Arc Plasma

P. Thoma

Page range: 808-819

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Abstract

Absolute helium emission coefficients have been measured from 540 nm down to 109 nm in the near vuv. The radiation originates from the axis of a cylindrical He-arc of 2 mm ∅ at one atmosphere with electron temperatures between 25000 K and 26500 K. The electron densities range from 3.0 · 10 16 cm -3 to 4.0 · 10 16 cm -3 and have been determined independently from other plasma parameters by means of line shape measurements. The density of atoms and their kinetic temperature have been calculated from the energy balance of the electrons and Dalton's law. Comparison of the measured helium continuum emission coefficients with theoretical calculations in the wavelength range from 540 nm to 400 nm shows that, in this experiment, the radiation due to bremsstrahlung in the field of atoms must not be neglected. Taking into account this contribution very good agreement with theoretical calculations over the whole investigated spectral range from 540 nm down to 109 nm has been found. Thus the present experiment confirms the theoretical results for the photoionisation coefficients from the n = 2 and n = 3 levels. On the basis of these results the helium continuum radiation may be used for calibration purposes, which is of particular interest in the vuv.

Open Access June 2, 2014

Proof of Kruszewski's Rule

Ivan Gutman

Page range: 820-822

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Abstract

A rule for the stability of isomeric polycyclic conjugated compounds, which was recently formulated by Kruszewski [1], is proved.

Open Access June 2, 2014

Exciton Phosphorescence of p-Terphenyl Crystal at 300 K

Eizi Morikawa, Masahiro Kotani

Page range: 823-827

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Abstract

Exciton phosphorescence from pure p-terphenyl crystals was observed at 300 K. The 0-0 band of the phosphorescence spectrum was found at 20.4 X 10 3 cm -1 . The vibrational progression of 1.46 x 10 3 cm -1 is present. The maximum exciton lifetime observed was 200 ms. The excitation spectrum of the exciton phosphorescence differs considerably from that observed in glassy solution, but is poorly structured as well. The absorption coefficient near the origin is small. The absence of sensitized delayed fluorescence from doped tetracene suggests that the triplet energy transfer to this guest is not diffusion limited.

Open Access June 2, 2014

Die spezifische Verbreiterung der FeI-Resonanzlinie 3859,91 Å durch Stöße mit Argonatomen bei hohen Temperaturen / Specific Line-Broadening of the Iron-Resonance-Line 3859,91 Å by Collisions with Argon Atoms at high Temperatures

J. Steinwandel, V. E. Joos, M. Hauser, Th. Dietz

Page range: 828-831

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Abstract

The specific line-broadening cross section of the FeI-resonance transition at 3859.91 Å by collision with argon atoms was measured in the temperature range of 2000 K ≦ T ≦ 3500 K in a shock tube. Driving gas was Helium, shock wave carrier gas and collision partner was Argon. The free iron atoms were produced by the unimolecular decomposition of ironpentacarbonyl in the front of the incident shock wave. The initially produced iron condensate evaporates completely in the reflected shock wave to form free atoms. They are present behind the reflected shock wave in the form of a thermodynamically well defined undersaturated vapour. Thermodynamic quantities of the vapour do not change during the observation time. The line-broadening cross section σ L (T) was measured by the method of integral atomic line absorption spectroscopy on the FeI-resonance line at 3859.91 Å to (10.05 ± 1.40) x 10 -15 cm 2 . Temperature variations in σ L are smaller than experimental errors.

Open Access June 2, 2014

Investigation of Rotational Relaxation by Double Resonance and Stark Switch Techniques

W. Schrepp, H. Dreizler, A. Guarnieri

Page range: 832-840

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Abstract

For the four rotational levels J K₋K₊ = 1 01 , 1 10 ,2 12 and 2 21 of ethylene oxide all possible four level double resonance experiments for dipole allowed transitions have been performed to investigate collisional effects and to determine the relative change of signal intensity, η = ⊿I/I, due to high power pump radiation. The T 1 and T 2 -relaxation times have been measured for all dipole allowed transitions within these four levels. A combination of the data obtained from both experimental methods allows the determination of rate and bath constants taking into account only first order dipolar transitions. No further restrictions have been used. This approximation is supported by a triple resonance experiment. In addition to the pure gas investigation in the absence of external fields, rotational relaxation has been studied in the presence of a static electric field and in a mixture with hydrogen.

Open Access June 2, 2014

EPR Study of the Nematic Liquid Crystals: PEBAB and EBRA

A. S. N. Rao, P. Narayana Murty, C. R. K. Murty, T. Rs. Reddy

Page range: 841-843

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Abstract

By EPR two nematic liquid crystals PEBAB and EBBA were investigated. The experimental variation of the order parameter with temperature is corroborated with theory. In EBBA a spectrum reminiscent of glassy nature is observed at - 60° C.

Open Access June 2, 2014

Photoelectron Spectroscopy of Heterocycles 1-(Diazinyl)-2-(Pyridyl)-ethenes (Triazastilbenes)

I. Novak, L. Klasinc, J. V. Knop, Th. Bluhm

Page range: 844-847

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Abstract

The photoelectron (PE) spectra of 1-(4-pyrimidyl)-2-(3-pyridyl)-ethene 1, 1-(2-pyrimidyl)-2- (3-pyridyl)-ethene 2, 1-(4-pyridazinyl)-2-(3-pyridyl)-ethene 3, 1-(3-pyridazinyl)-2-(3-pyridyl)- ethene 4 and 1-(2-pyrazinyl)-2-(3-pyridyl)-ethene 5 all in their trans conformations have been recorded using Hel radiation. Comparisons with the PE spectra of styrylpyridines, dipyridylethenes and diazabenzenes allowed the assignment of all ionization energies, E i , corresponding to π- and nitrogen lone pair ionizations in the region of E i < 12 eV. The variations in PE spectra of five isomeric triazastilbenes studied are due to different nitrogen atom positions in the diazinyl ring.

Open Access June 2, 2014

On the Internal Motion of Iron Chloride Molecules

Magdolna Hargittai, Jon Brunvoll

Page range: 848-851

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Abstract

The vibrationally averaged structures of the iron chloride molecules may considerable differ from their equilibrium structure as a consequence of low-frequency large amplitude vibrations. Mean amplitudes of vibration and perpendicular amplitude correction terms have been calculated for FeCl 2 and FeCl 3 . Mean amplitudes of vibration have also been calculated for D2h (equilibrium structure) and C 2v (vibrationally averaged structure) symmetry forms of Fe 2 Cl 4 and Fe 2 Cl 6 -The applicability of normal coordinate analysis for high temperature systems with large amplitude motion is discussed.

Open Access June 2, 2014

1,2,4-Triazole Complexes XII * . Magnetic properties of Fe (1, 2, 4-triazole)₂ (NCS)₂, a quasi two-dimensional S = ½. antiferromagnet with hidden canting.

D. W. Engelfriet, W. L. Groeneveld, G. M. Nap

Page range: 852-864

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Abstract

Fe(trz) 2 (NCS) 2 has been investigated by means of magnetic susceptibility and magnetization measurements on single crystals at temperatures 1.8-300 K, heat capacity measurements at 1.5-90 K and neutron powder diffraction at 1.2 K. The compound orders antiferromagnetically at T c = 8.46(2) K. The susceptibilities along the orthorhombic axes are strongly anisotropic, the a axis being the preferred direction. The susceptibility data along a and the heat capacity results are in reasonable agreement with the predictions for the quadratic layer, S = ½. Ising antiferromagnet, with an intralayer exchange constant J/k = - 7.2(2) K. Below T c the magnetization curve along the a axis reveals a metamagnetic transition at 1.74 kOe. In accordance with the Ising-like properties, a direct transition from the antiferromagnetic to the paramagnetic state is observed along a at 50 kOe. Hidden canting is found to be present. At 1.2 K the compound appears to be monoclinically distorted with α = 88.3° (with respect to Aba2, the space group at 300 K). The magnetic structure consists probably of four sublattices with the magnetic moments lying in the planes z = 0 and z =½ (with respect to the distorted cell in Aba2) along directions that are at an angle of 8° with the a axis. Ligand bonding parameters are discussed in terms of the angular overlap model.

Open Access June 2, 2014

Untersuchungen zur Anwendbarkeit des CNDO/S-CI-Verfahrens für die Berechnung der Anregungsenergien organischer Verbindungen am Beispiel von Phthalsäurederivaten / Investigations on the Applicability of the CNDO/S-CI method for the Calculation of Excitation energies of Organic compounds using Derivatives of Phthalic acid as Examples

Walter Fabian

Page range: 865-868

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Abstract

The influence of the choice of geometrical parameters and the approximations used to evaluate the two centre coulombic integrals upon excitation energies as calculated by the CNDO/S-or INDO/S-CI method is discussed.

Open Access June 2, 2014

Repulsion Phenomena in Thin Layers of Alcoholic Solutions of Tetrabutylammonium Iodide

G. Peschel, P. Belouschek

Page range: 869-875

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Abstract

The structural disjoining pressure of methyl-, ethyl-, n-propyl, and n-butyl alcohol was deter-mined in thin layers between highly smooth rutile surfaces when tetrabutylammonium iodide was added. The a verage thickness of the oriented solvation layers per interface turned out to be largest for methyl alcohol (about 1.5 nm) and decreases like the disjoining pressure when passing to the related alcohols with longer chain lengths. Tetrabutylammonium iodide clearly reduces the thickness of the boundary layer with increasing concentration.

Open Access June 2, 2014

Calculation of the Lifetimes of Localized Electronic Vacancies in Cyclic Molecules

R. Spehr

Page range: 876-882

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Abstract

For a benzenelike ring of six carbon atoms the dissipation of localized electron vacancies of π and of σ symmetry is calculated. The vacancies are described by Wannier sums. The calculation yields lifetimes of localization of about 10 - 16 s in both cases. These values are shorter by two orders of magnitude than any period of molecular vibrations. Therefore such transiently localized vacancies, which can be caused by irradiation or by statistical fluctuations, will not destroy any bond in organic molecules.

Open Access June 2, 2014

Limitations on Mass Separation by the Weakly Ionized Plasma Centrifuge

M. M. B. Wijnakker, E. H. A. Granneman

Page range: 883-893

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Abstract

bstract A In weakly ionized argon and xenon rotating plasmas the rotational velocity and the temperature and pressure distribution have been measured. The stationary discharge is generated by two opposed cathode-anode configurations. The arc current of 100 A is drawn across an axial magnetic field up to 0.26 T. The filling pressure ijs varied between 1 and 10 torr. The rotational velocity is found to be proportional to the discharge current and the magnetic field and inversely proportional to the viscosity of the neutral gas. The rotational kinetic energies of the particles in the argon and xenon discharge are about equal. Because the temperature of the argon discharge is lower than that of the xenon discharge, the pressure rise in radial direction due to centrifugal forces is steeper for the former. A theoretical analysis taking into account viscous dissipation as the only heating mechanism yields a heavy particle temperature T which imposes an upper limit to the ratio X =½m υ θ 2 /kT of order unity. The maximum attainable separation factor α is therefore limited in these types of centrifuges. Experimentally, in the parameter region studied, X is found not to exceed a value 0.4 in argon discharges and 0.2 in xenon discharges. A rough estimate shows that besides viscous dissipation other heating mechanisms are also important. Ohmic heating, for instance, is at least a factor 6 larger than the viscous dissipation.

Open Access June 2, 2014

Über einige präparative Probleme zum Hexachlorotechnetat und ihren Einfluß auf die Messung der Zerfallskonstanten des ^99mTc in Hexahalogenokomplexen / About some preparative problems concerning hexachlorotechnetate and their influence on the measuring of the decay constant of ^99mTc in hexahalogeno complexes.

K.-P. Dostal, B. Bayerl

Page range: 894-895

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Abstract

A discrepancy between theoretical and experimental values concerning the variation of decay constant of 99m Tc is cleared up. A new preparation of hexachlorotechnetate complex by reduction of pertechnetate ion with hydrazine is given. The corrected experimental results are λ(TcO 4 -) -λ(TcCl 6 --) = (1,93 ± 0,12) · 10 -3 1λ, λ(TcO 4 -) -λ(TcBr 6 --) = (2,44 ± 0,30) · 10 -3 λ, λ(TcO 4 -) -λ(TcJ 6 --) = (3,22 ± 0,29) · 10 -3 λ.

Open Access June 2, 2014

Die Viskositätsabhängigkeit der Fluoreszenz - Anisotropie und der Lebensdauer von Trans-Stilben / Influence of Viscosity upon the Anisotropic Fluorescence and Lifetime of trans-Stilbene

M. Alicka, R. K. Bauer, A. Kawski

Page range: 896-897

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Abstract

The fluorescence anisotropy r and lifetime τ F of trans-stilbene in different solvents has been measured and the dielectric relaxation time from Perrin and Debye equations has been determined. The fluorescence lifetime in the viscosity region from 0.321 to 61.92 Nm -2 s, varies between 30 and 152 ps.

Open Access June 2, 2014

Errata

Page range: 898-898

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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

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

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Volume 35 Issue 8

Issue of Zeitschrift für Naturforschung A

Origin of Iron Meteorite Groups IAB and IIICD

Abstract

Unification of Brueckner Theory and HFB Theory

Abstract

Absolutmessung der kontinuierlichen Strahlung des Heliums im Lichtbogen von λ = 109 bis 540 nm / Measurement of the Helium Continuum Radiation from λ = 109 to 540 nm in an Arc Plasma

Abstract

Proof of Kruszewski's Rule

Abstract

Exciton Phosphorescence of p-Terphenyl Crystal at 300 K

Abstract

Die spezifische Verbreiterung der FeI-Resonanzlinie 3859,91 Å durch Stöße mit Argonatomen bei hohen Temperaturen / Specific Line-Broadening of the Iron-Resonance-Line 3859,91 Å by Collisions with Argon Atoms at high Temperatures

Abstract

Investigation of Rotational Relaxation by Double Resonance and Stark Switch Techniques

Abstract

EPR Study of the Nematic Liquid Crystals: PEBAB and EBRA

Abstract

Photoelectron Spectroscopy of Heterocycles 1-(Diazinyl)-2-(Pyridyl)-ethenes (Triazastilbenes)

Abstract

On the Internal Motion of Iron Chloride Molecules

Abstract

1,2,4-Triazole Complexes XII * . Magnetic properties of Fe (1, 2, 4-triazole)2 (NCS)2, a quasi two-dimensional S = ½. antiferromagnet with hidden canting.

Abstract

Abstract

Repulsion Phenomena in Thin Layers of Alcoholic Solutions of Tetrabutylammonium Iodide

Abstract

Calculation of the Lifetimes of Localized Electronic Vacancies in Cyclic Molecules

Abstract

Limitations on Mass Separation by the Weakly Ionized Plasma Centrifuge

Abstract

Abstract

Die Viskositätsabhängigkeit der Fluoreszenz - Anisotropie und der Lebensdauer von Trans-Stilben / Influence of Viscosity upon the Anisotropic Fluorescence and Lifetime of trans-Stilbene

Abstract

Errata

1,2,4-Triazole Complexes XII * . Magnetic properties of Fe (1, 2, 4-triazole)₂ (NCS)₂, a quasi two-dimensional S = ½. antiferromagnet with hidden canting.