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Volume 42 Issue 7

Issue of Zeitschrift für Naturforschung A

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Open Access June 2, 2014

An Intuitive Understanding of Black-Hole Evaporation by Viewing it in Terms of More Familiar Quantum-Field Effects in Flat Spacetime

R. M. Nugayev

Page range: 657-662

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Abstract

The article is aimed at an intuitive understanding of the recently explored deep connections between therm al physics, quantum field theory and general relativity. The physical effects involved in particle creation by a black hole are viewed in terms of more familiar quantum -field effects in flat spacetime. Black hole evaporation is investigated in terms of temperature correction to the Casimir effect. T he application of the Casimir effect results and those for accelerated mirrors reveals that a black hole should produce the blackbody radiation at a temperature that exactly coincides with Hawking’s result. Its blackbody nature is due to the interaction of virtual positive-energy particles with the surface of a “cavity” formed by the Schwarzchild gravitational field potential barrier. The virtual particles are “squeezed out” by the contraction of the potential barrier and appear to an observer at J + as the real blackbody ones.

Open Access June 2, 2014

Why is G the Least Precisely Known Physical Constant?

C. C. Speake, G.T. Gillies

Page range: 663-669

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Abstract

CODATA has recently published its readjustment of the fundamental physical constants and assigns a relative precision of 128 x 10 -6 to G, the Newtonian constant of gravitation. Given that most of the other constants in physics have relative precisions of ~10 -6 or better, we examine the reasons why the value for G remains so imprecise: The role of G in physics in general is considered and the most recent experimental determinations are examined. Constraints are given for perturbing effects in G measurements and a key result is that horizontal ground movements must be taken more carefully into account in future more precise terrestrial experiments.

Open Access June 2, 2014

Band Structure Calculations of Two-Dimensional (2 D) Models of the Phases LiBC and CaAl₂Si₂

Rafael Ramirez, Reinhard Nesper, Hans Georg von Schnering, Michael C. Böhm

Page range: 670-682

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Abstract

The electronic structures of the phases LiBC and CaAl 2 Si 2 have been investigated by two dimensional crystal orbital calculations. The corresponding solid-state ensembles have been separated into anionic (e.g. [BC] - , [AlSi] - , [Al 2 Si 2 ] 2- ) and cationic substructures. The employed fragmentation is topologically related to the electron counting schemes used in the classical Zintl approach. The band structures of the anionic fragments have been determined by a semiempirical Hartree-Fock crystal orbital (CO ) Hamiltonian on the basis of the tight-binding approximation. The adopted self-consistent-field variant is an intermediate neglect of differential overlap (INDO ) scheme. The influence of the cationic substructure has been simulated by an electrostatic point-charge model. The computational formalism allows for a suitable explanation of the conformations of the anionic subunits of the studied solids. In the CaAl 2 Si 2 model the site symmetry in the anionic substructure has been studied in larger detail. The Al atoms show a tetrahedral coordination while an inverted tetrahedron (i.e. umbrella-like structure) is realized at the more electronegative Si centers. This local geometry is stabilized by the Coulomb interaction between the anionic [Al 2 Si 2 ] 2- layer and the cationic substructure. The energetic sources leading to the different conformations in LiBC and CaAl 2 Si 2 are also quantified. The observed geometric preferences are rationalized by means of an energy fragmentation into covalent resonance (kinetic energy of the electrons) and classical Coulomb elements. This energy decomposition in the planar and chair-like conformations of LiBC and CaAl 2 Si 2 shows that the kinetic energy favours the former, the electrostatic part the latter conformation. The dimerization of two anionic substructures (CaAl 2 Si 2 structure) is also studied by the tight-binding formalism . The observed geometric differences between intra- and interlayer bonds are satisfactorily reproduced by the semiempirical CO model.

Open Access June 2, 2014

Internal Cation Mobilities and Their Isotope Effects in the Molten System (Li, K)NO₃

Arnold Lundén, Junko Habasaki, Isao Okada

Page range: 683-689

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Abstract

With the Klemm method internal mobility ratios of the two cations have been measured for melts of the binary system (Li, K ) NO 3 over a wide range of temperature and composition, and their isotope effects have been determined near the eutectic composition. The Chemla effect has been observed. With increasing temperature the Chemla crossing point shifts, as expected, toward higher concentrations of the smaller cation. At very high concentrations of LiNO 3 the mobility of K + tends to decrease, which is attributed to the free space effect. For both Li + and K + the isotope effect increases with temperature.

Open Access June 2, 2014

Molar Volume and Surface Tension of Molten LaCl₃-KCl Mixtures

K. Igarashi

Page range: 690-694

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Abstract

Molar volumes and surface tensions of molten LaCl 3 -KCl mixtures were measured by dilatometry and the maxim um bubble pressure method, respectively. The molar volume isotherms were found to deviate positively from additivity over the whole composition range, with the maxim um deviation at ca. 30 mol% LaCl 3 . At the same concentration the isotherms of surface tension at temperatures below 950 °C show a minimum . Surface energy of mixing per unit area calculated from the surface tensions shows a large negative excess at the corresponding composition. These observations are related to the existence o f LaCl 6 3- in the KCl-rich melt.

Open Access June 2, 2014

Internal Cation Mobilities in the Molten Binary System KNO₃ — Ca(NO₃)₂

Junko Habasaki, Chao-cheng Yang, Isao Okada

Page range: 695-699

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Abstract

Internal mobility ratios in the molten binary system KNO 3 - Ca 0.5 NO 3 have been measured with the Klemm method in a range up to 50 mol% Ca 0.5 NO 3 . From these and available data on the densities and conductivities, the internal mobilities of K + and Ca 2+ ions (b K and b Ca , respectively) have been calculated. With an increase of Ca 2+ concentration, both b K and b Ca decrease. The decrease of b K is presumed to be attributable to the “tranquillisation effect” caused by clustering of NO 3 - ions around Ca 2+ ions due to the strong Coulombic interaction. The increase of b Ca with increasing concentration o f K + ions may be attributed to the agitation effect by K+ ions.

Open Access June 2, 2014

The Isotope Effect of Li⁺ Ions in Electromigration of Molten LiNO₃

Akira Endohand, Isao Okada, Masao Nomura, Makoto Okamoto

Page range: 700-704

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Abstract

The relative difference in internal mobilities o f 6 Li and 7 Li, ε, in molten LiNO 3 has been remeasured in the temperature range from 559 K to 726 K by countercurrent electromigration (Klemm 's method). As temperature increases, the isotope effect increases, although the increasing rate decreases: it is practically constant above 650 K. The ε values are lower than those measured by Lundén and Ekhed [5] by 15-25% . The effective diffusion coefficients have been estimated from the distribution of the isotopes in the separation tube by numerical simulation.

Open Access June 2, 2014

Extended Analysis of the K = 3 Inversion-Rotation Doublets for ¹⁴ND₃ and ,¹⁵ND₃ in the ν₂ = 1 Excited State

J. Doose, W. Neustock, A. Guarnieri

Page range: 705-708

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Abstract

Several K = 3 doublets of 14 ND 3 and 15 ND 3 in the ν2 = 1 excited vibrational state have been observed. With the new lines we were able to obtain improved values for the η 3 0 and η 3 J constants. For 14 ND 3 η 3 0 = 2.3517(15) · 10 -5 MHz, η 3 J = -1.068(8) ·10 -8 MHz, and for 15 ND 3 η 3 0 = 2.3548(23) · 10 -5 MHz, η 3 J = 1.061(10)· 10 -8 MHz.

Open Access June 2, 2014

Temperature Dependence of Lithium Isotope Effects in Ion Exchange Electromigration

Yasuhiko Fujii, Morikazu Hosoe, Okamoto Makoto

Page range: 709-712

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Abstract

The isotope separation coefficient of lithium electromigration through a cation exchange membrane is determined at 6, 11, 20 and 40 °C . It is found that this coefficient increases with temperature while the slope of the isotope distribution in the band decreases with increasing temperature. These tendencies are opposite to those usually observed in ion exchange chromatography.

Open Access June 2, 2014

Zur spektroskopischen Analyse von Reaktionen zweiter Ordnung

Heinz Mauser

Page range: 713-721

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Abstract

In the first part of this work [1] it was shown that it is possible to analyse kinetically uniform reactions of second order using only spectroscopic methods. No knowledge of the coefficients of extinction is needed. Now systems are discussed in which there are two linearly independent progress variables. New studies by Polster [2] are demonstrating the success of the methods described here.

Open Access June 2, 2014

Enumeration of Kekulé Structures for Multiple Zigzag Chains and Related Benzenoid Hydrocarbons

S. J. Cyvin, B. N. Cyvin

Page range: 722-730

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Abstract

The benzenoid classes of multiple zigzag chains, A (n, m ), and incomplete multiple zigzag chains. A (n, m, l), are considered. Numerical numbers of Kekulé structures (K ) are given for n up to 5 and m up to 10. A recurrence relation is developed for the K numbers of A(n, m) with fixed values of n; a general formulation for arbitrary m values was achieved. Six new benzenoid classes are studied in connection with the application of the John-Sachs theorem to double zigzag chains. A new approach to the K enumeration is introduced by nonlinearly dependent recurrence relations. Finally a new type of combinatorial K formulas in terms of determinants and based on the John-Sachs theorem , is introduced. The new enumeration techniques are applied to multiple zigzag chains.

Open Access June 2, 2014

Assessment of the Accuracy of the Quasiclassical Trajectories Approximation at a Low Collision Energy for the He — N₂ System

Aristophanes Metropoulos

Page range: 731-734

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Abstract

We have computed rotational energy transfer differential and state-to-state integral quasiclassical cross sections for the He - N 2 system at 27.3 meV. By comparing these differential cross sections to close coupling ones, the accuracy of the quasiclassical approximation at such a low collision energy has been assessed as satisfactory.

Open Access June 2, 2014

Empirical Quantitative Relationship between Molecular Structure and Phosphorescence Transition Energy of Polycyclic Aromatic Thiophenes

Maximilian Zander, Jürgen Jacob, Milton L. Lee

Page range: 735-738

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Abstract

Empirical quantitative models have been studied that relate the phosphorescence transition energies of thiophene benzologs and corresponding aromatic hydrocarbon systems. Phosphorescence 0,0 bands, phosphorescence/fluorescence quantum yield ratios, and phosphorescence lifetimes of 12 thiophene benzologs of which the phosphorescence properties were unknown are reported.

Open Access June 2, 2014

On the Phase Transition of Bis(pyridinium)hexachlorometallates, (C₅H₅NH)₂[MCl₆], M = Sn, Te, Pb, Pt. An X-Ray and ³⁵Cl NQR Study

Dirk Borchers, Alarich Weiss

Page range: 739-748

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Abstract

A phase transition has been observed in bis(pyridinium) hexachlorometallates (C 5 H 5 NH) 2 [M IV Cl 6 ]. M = Sn. Te. Pb. Pt. The crystal structure of the low temperature phase II of the salt with M = Sn was determined, space group C 1 ḷ - P 1̅, Z = 1 (a = 734.1pm, b = 799.0 pm, c = 799.7 pm,α= 83.229°. β = 65.377°, γ= 84.387°, T = 297 K). The four compounds are isotypic in phase II as well as in the high temperature phase I (C 2H 2 -B2 /m, Z = 2) for which the crystal structure is known for M = Te . The lattice constants of all compounds (both phases) are given. The temperature dependence of the 35 Cl NQR spectrum was investigated. The three line 35 Cl NQR spectrum is in agreement with the crystal structure. The dynamics of the pyridinium ring shows up in a fade out of part of the 35 Cl NQR spectrum . The influence o f H ↔ D exchange on 35 Cl NQR is studied and an assignment of ν ( 35 Cl) ↔ Cl (i) is proposed. The nature of the phase transition P1̅ (Z = 1) ↔ B2 /m (Z = 2) is discussed.

Open Access June 2, 2014

Calculation of the Polarisability and Second Hyperpolarisability of Ferrocene, Fe(C₅H₅)₂, Using the Extended CHF-PT-EB-CNDO Method

J. Waite, M. G Papadopoulos

Page range: 749-752

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Abstract

The polarisability and second hyperpolarisability of ferrocene have been calculated using the CHF -PT -EB -CNDO method, which has been extended for the study of compounds containing transition metal elements. The computed polarisability value is in good agreement with experiment.

Open Access June 2, 2014

The Calculation of ¹⁴N Quadrupole Coupling Constants with Basis Sets of High Local Quality

Stefan Gerber, Hanspeter Huber

Page range: 753-760

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Abstract

An appropriate basis set to obtain electric field gradients close to the Hartree-Fock limit is evaluated for the nitrogen nucleus. An empirical correction for the error due to the neglect of electron correlation is given for sp-, sp 2 - and sp 3 -hybrized nitrogen. The results are used to predict the full quadrupole coupling tensor for a few molecules. A breakdown of the electric field gradient into contributions from the single orbitals leads to a model for the field gradient due to the π-system and a partial rationalization of the part due to the σ-system. The results are discussed in relation to a Townes and Dailey analysis.

Open Access June 2, 2014

A Theoretical Study of 2-Substituted Allyl Cations and Anions

Salim M. Khalil

Page range: 761-766

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Abstract

MINDO-Forces calculations are reported, after complete geometry optimization, for 2-X-allyl cations and anions, where X is O - , OH, NH 2 , CH 3 , NO 2 , CN, CF 3 , F, CHO.In the case of the allyl cation, it was found that the substituents O - , OH, NH 2 are stabilizing, CH 3 is slightly stabilizing and all other substituents are destabilizing.In the case of the allyl anions, all the substituents are stabilizing. It was found that the substituents CH 3 , O - , CN show the amphielectronic behaviour. Calculations predict no (1,3) π interaction in 2-substituted ally cations and anions.

Open Access June 2, 2014

Chemical Hardness and L. Pauling’s Scale of Electronegativity

Ludwik Komorowski

Page range: 767-773

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Abstract

The energy of the charge transfer interaction is expressed using absolute electronegativities and hardness parameters. The master equation appears to bind together Pauling and Mulliken scales by the factor (7/4 π ε 0 ) 1/2 = 3.174 V 1/2 nm 1/2 electron -1/2 . An index of charge transfer affinity (CTA) is proposed as possible measure of the tendency to ionic bonding between atoms.

Open Access June 2, 2014

Thermal and X-Ray Studies of 1,6-Bis-[4-(trans-4-n-propylcyclohexyl) phenyl]-hexane and 3,5-Bis-[4-(trans-4-n-propylcyclohexyl) phenyl]-1,2,4-thiadiazol

I. H. Ibrahim, W. Haase

Page range: 774-776

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Abstract

The liquid crystalline phases of the title compounds have been investigated by differential scanning calorimetry, optical microscopy and X -ray diffraction methods. Transition temperatures and transition enthalpies of these compounds have been determined. The diffraction photographs in the nematic phase of the first compound showed diffraction patterns corresponding to two coexisting mass density fluctuations with commensurate wavelengths, whereas a single diffraction pattern was observed in the nematic phase of the second compound. The thermal and X -ray data showed that the first compound has a quasi-smectic layer structure.

Open Access June 2, 2014

Notizen: Volume Changes on Melting for Several Rare Earth Chlorides

K. Igarashi, J. Mochinaga

Page range: 777-778

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Abstract

Molar volumes in the liquid state and melting points of several rare earth chlorides RCl 3 (R = La, Pr, Nd, Gd, Dy, and Y) have been measured by dilatometry and DTA. respectively. The volume changes on melting of these chlorides were evaluated on the basis of these result and available crystal structure data. The volume increase on melting of the hexagonal chlorides from LaCl 3 to GdCl 3 was found to be more than 20%. On the other hand, the volume changes of the monoclinic DyCl 3 and YCl 3 were less than 1%.

Open Access June 2, 2014

Notizen: Mittlere Schwingungsamplituden von Chromylbromid

Ana C. González-Baró

Page range: 779-780

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Abstract

Mean amplitudes of vibration of CrO 2 Br 2 in the temperature range between 0 and 1000 K have been calculated from recently reported spectroscopic data. The results are briefly discussed and compared with those of CrO 2 F 2 and CrO 2 Cl 2 .

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 & Optical Physics
Chemical Physics
Dynamical Systems & Nonlinear Phenomena
Fundamental Concepts of Physical Sciences
Gravitation & Cosmology
Hydrodynamics & Plasma Physics
Nuclear Physics & Particle Physics
Quantum Field 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 42 Issue 7

Issue of Zeitschrift für Naturforschung A

An Intuitive Understanding of Black-Hole Evaporation by Viewing it in Terms of More Familiar Quantum-Field Effects in Flat Spacetime

Abstract

Why is G the Least Precisely Known Physical Constant?

Abstract

Band Structure Calculations of Two-Dimensional (2 D) Models of the Phases LiBC and CaAl2Si2

Abstract

Internal Cation Mobilities and Their Isotope Effects in the Molten System (Li, K)NO3

Abstract

Molar Volume and Surface Tension of Molten LaCl3-KCl Mixtures

Abstract

Internal Cation Mobilities in the Molten Binary System KNO3 — Ca(NO3)2

Abstract

The Isotope Effect of Li+ Ions in Electromigration of Molten LiNO3

Abstract

Extended Analysis of the K = 3 Inversion-Rotation Doublets for 14ND3 and ,15ND3 in the ν2 = 1 Excited State

Abstract

Temperature Dependence of Lithium Isotope Effects in Ion Exchange Electromigration

Abstract

Zur spektroskopischen Analyse von Reaktionen zweiter Ordnung

Abstract

Enumeration of Kekulé Structures for Multiple Zigzag Chains and Related Benzenoid Hydrocarbons

Abstract

Assessment of the Accuracy of the Quasiclassical Trajectories Approximation at a Low Collision Energy for the He — N2 System

Abstract

Empirical Quantitative Relationship between Molecular Structure and Phosphorescence Transition Energy of Polycyclic Aromatic Thiophenes

Abstract

On the Phase Transition of Bis(pyridinium)hexachlorometallates, (C5H5NH)2[MCl6], M = Sn, Te, Pb, Pt. An X-Ray and 35Cl NQR Study

Abstract

Calculation of the Polarisability and Second Hyperpolarisability of Ferrocene, Fe(C5H5)2, Using the Extended CHF-PT-EB-CNDO Method

Abstract

The Calculation of 14N Quadrupole Coupling Constants with Basis Sets of High Local Quality

Abstract

A Theoretical Study of 2-Substituted Allyl Cations and Anions

Abstract

Chemical Hardness and L. Pauling’s Scale of Electronegativity

Abstract

Thermal and X-Ray Studies of 1,6-Bis-[4-(trans-4-n-propylcyclohexyl) phenyl]-hexane and 3,5-Bis-[4-(trans-4-n-propylcyclohexyl) phenyl]-1,2,4-thiadiazol

Abstract

Notizen: Volume Changes on Melting for Several Rare Earth Chlorides

Abstract

Notizen: Mittlere Schwingungsamplituden von Chromylbromid

Abstract

Band Structure Calculations of Two-Dimensional (2 D) Models of the Phases LiBC and CaAl₂Si₂

Internal Cation Mobilities and Their Isotope Effects in the Molten System (Li, K)NO₃

Molar Volume and Surface Tension of Molten LaCl₃-KCl Mixtures

Internal Cation Mobilities in the Molten Binary System KNO₃ — Ca(NO₃)₂

The Isotope Effect of Li⁺ Ions in Electromigration of Molten LiNO₃

Extended Analysis of the K = 3 Inversion-Rotation Doublets for ¹⁴ND₃ and ,¹⁵ND₃ in the ν₂ = 1 Excited State

Assessment of the Accuracy of the Quasiclassical Trajectories Approximation at a Low Collision Energy for the He — N₂ System

On the Phase Transition of Bis(pyridinium)hexachlorometallates, (C₅H₅NH)₂[MCl₆], M = Sn, Te, Pb, Pt. An X-Ray and ³⁵Cl NQR Study

Calculation of the Polarisability and Second Hyperpolarisability of Ferrocene, Fe(C₅H₅)₂, Using the Extended CHF-PT-EB-CNDO Method

The Calculation of ¹⁴N Quadrupole Coupling Constants with Basis Sets of High Local Quality