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1976 (300)
1Author    Berndt Müller, Walter GreinerRequires cookie*
 Title    The Two Centre Dirac Equation  
 Abstract    During collisions of heavy ions with heavy targets below the Coulomb barrier, adiabatic molecular orbitals are formed for the inner electrons. Deviations from adiabaticity lead to coupling between various states and can be treated by time-dependent perturbation theory. For high charges (Z1+Z2 60) the molecular electrons are highly relativistic. Therefore, the Dirac equation has to be used to obtain the energies and wave functions. The Dirac Hamiltonian is transformed into the intrinsic rotating coordinate system where prolate spheroidal coordinates are introduced. A set of basis functions is proposed which allows the evaluation of all matrix elements of the Dirac Hamil-tonian analytically. The resulting matrix is diagonalized numerically. The finite nuclear charge distribution is also taken into account. Results are presented and discussed for various charac-teristic systems, e. g. 
  Reference    (Z. Naturforsch. 31a, 1—30 [1976]; received November 14 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0001.pdf 
 Identifier    ZNA-1976-31a-0001 
 Volume    31 
2Author    R. V. Gopala Rao, T. NammalvarRequires cookie*
 Title    A Note on the Self Consistent Approximation Method for the Evaluation of Radial Distribution Functions of Simple Fluids  
 Abstract    The self consistent approximation of Rowlinson, Carley and Lado has been applied to calculate the radial distribution functions of simple fluids (Neon, Krypton and Xenon) interacting with a Lennard-Jones 6:12 potential. It has been found that in general the self consistent values are nearer to the exact values than other values. 
  Reference    (Z. Naturforsch. 31a, 31—33 [1976]; received April 22 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0031.pdf 
 Identifier    ZNA-1976-31a-0031 
 Volume    31 
3Author    R. Shanker, R. A. SinghRequires cookie*
 Title    Effect of Anisotropy on the Critical Behaviour of Three- Dimensional Heisenberg Ferromagnets  
 Abstract    The anisotropic nearest-neighbour Heisenberg model for the simple cubic lattice has been in-vestigated by interpolating the anisotropy between the Ising and isotropic Heisenberg limits via general spin high-temperature series expansions of the zero-field suspectibility. This is done by estimating the critical temperature (7V 3>) and the susceptibility exponent y from the analysis of the series by the Ratio and Pade approximants methods. It is noted that 7V 3) varies with anisotropy while y is almost the same for the anisotropic system, and a jump in it occurs for the isotropic case in agreement with the universality hypothesis. The effect of anisotropy on the susceptibility is also shown. Further, it is seen that estimates of y for the two extreme limits agree well with those of previous theoretical as well as experimental investigations. In addition, critical tempera-tures have been summarised in a relation, and expressions for the magnetisation have been derived. 
  Reference    (Z. Naturforsch. 31a, 34—40 [1976]; received September 15 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0034.pdf 
 Identifier    ZNA-1976-31a-0034 
 Volume    31 
4Author    Fred FischerRequires cookie*
 Title    Critical Pitch in Thin Cholesteric Films with Homeotropic Boundaries  
 Abstract    Calculations of the planar cholesteric texture with homeotropic boundary conditions are pre-sented. At a constant film thickness there is a critical twist Joe below which the planar texture has transformed into a homeotropic one. The additional influence of an external field is discussed for positive and negative anisotropy and with field orientations parallel or normal to the film plane. A general solution of the director field has been found for a normal orientation of the field. A properly adjusted twist t0 obtained by dilution of an optically active material in a nematic matrix opens a possibility to reduce the critical voltage in technical devices. 
  Reference    (Z. Naturforsch. 31a, 41—46 [1976]; received November 24 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0041.pdf 
 Identifier    ZNA-1976-31a-0041 
 Volume    31 
5Author    Henner Ruppersberg, Walter SpeicherRequires cookie*
 Title    Density and Compressibility of Liquid Li-Pb Alloys  
 Abstract    The density and the velocity of sound of liquid Li-Pb alloys have been measured in the composi-tion ranges 0 — 17, 30 — 100 at % Pb and 0—10, 40 — 100 at % Pb, respectively. The temperature dependence of these properties has been determined for each sample in a temperature range of at least 130 K. The excess volume is negative and has a minimum at about 20at%Pb, where the vol-ume per atom at 800 °C is about 19% smaller than the volume of an ideal solution. The absolute value of the excess volume rises with the temperature, as does the absolute value of the deviation of the adiabatic compressibility from the mean compressibility. 
  Reference    (Z. Naturforsch. 31a, 47 [1976]; eingegangen am 25. November 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0047.pdf 
 Identifier    ZNA-1976-31a-0047 
 Volume    31 
6Author    OttoL. Stiefvater, K., Stephen Lui, JohnA. LaddRequires cookie*
 Title    The Microwave Spectrum of 2,6-Difluoropyridine II. Dipole Moment, Quadrupole Coupling Constants and Vibrational Satellites  
 Abstract    Hyperfine splittings of rotational transitions of 2,6-difluoropyridine have been analysed to yield the 14 N quadrupole coupling constants. Their values are: Xaa = 1.82 ±0.05 MHz, Xbb = -4.16 ±0.02 MHz, Xcc = 2.34 ±0.05 MHz. The electric dipole moment has been determined from Stark effects as fi = 3.82 ± 0.06 D, and satellites in the rotation spectrum have been correlated with the five lowest fundamental vibrations of this molecule. The dipole moment, the quadrupole data and the structural differences between 2,6-difluoro-pyridine and pyridine itself can all be accounted for by the change in the electron distribution due to the fluorine substituents. 
  Reference    (Z. Naturforsch. 31a, 53—60 [1976]; received November 28 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0053.pdf 
 Identifier    ZNA-1976-31a-0053 
 Volume    31 
7Author    J. Friedrich, J. Vogel, W. Windhager, F. DörrRequires cookie*
 Title    Deuterium Isotope Effect in the Radiative Triplet Decay of Heavy Atom Substituted Aromatic Molecules  
 Abstract    We studied the effect of deuteration on the radiative decay of the triplet sublevels of naph-thalene and some halogenated derivatives. We found that the influence of deuteration is much more pronounced in the heavy atom substituted than in the parent hydrocarbons. The strongest change upon deuteration is in the radiative decay of the out-of-plane polarized spin state T x . These findings are consistently related to a second order Herzberg-Teller (HT) spin-orbit coupling. Though we found only a small influence of deuteration on the total radiative rate in naphthalene, a signi-ficantly larger effect is observed in the rate of the 00-transition of the phosphorescence. This result is discussed in terms of a change of the overlap integral of the vibrational groundstates of Tx and S0 upon deuteration. 
  Reference    (Z. Naturforsch. 31a, 61—70 [1976]; received December 6 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0061.pdf 
 Identifier    ZNA-1976-31a-0061 
 Volume    31 
8Author    H. Sterk, A. WachmannRequires cookie*
 Title    Zum Mechanismus der 6 JHH-Kopplungen in bicyclischen Systemen  
 Abstract    Concerning the Mechanism of 9 JHH Couplings in Bicyclic Systems Experimental investigations on bicyclic aromatic systems show the missing of an exocyclic long range coupling. The explanation for this fact can be found by assuming that the through space mechanism owns a greater influence on the amount of the long range coupling constants. On the basis of the different amounts of through space interaction between para-and exocyclic couplings the experimental results can be explained. 
  Reference    (Z. Naturforsch. 31a, 71 [1976]; eingegangen am 4. Dezember 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0071.pdf 
 Identifier    ZNA-1976-31a-0071 
 Volume    31 
9Author    K. Doblhofer, K. P. Charlé, D. VeltwisdiRequires cookie*
 Title    Secondary Electron Emission from Conductive, Liquid Polyethylene Glycol 1500  
 Abstract    A thorough study of the secondary electron emission (SEE) yield from liquid Polyethylene glycol 1500 (PEG) was made. This liquid (m. p. 45 °C) has a low enough vapor pressure at a working temperature of about 50 °C. In addition, it has the advantage of being a good solvent for salts which dissociate and thus render the solutions conductive. It was found that the presence of the electrolyte salt does not affect the secondary electron yield curves. A striking result is that the yield curves obtained from the PEG solutions are very well repro-ducible (ca. + 7%). By fitting the experimental data to a formula given by the elementary theory of SEE it can be clearly seen that this liquid polymer shows quite a different SEE behaviour compared with that reported for chemically similar solid polymer films. The results obtained agree well with the data for polymer silicon oils, suggesting that liquid polymers differ in their SEE behaviour from the corresponding solids. Finally, it is demonstrated that the reduced yield curves can be fitted to the physically meaning-ful Bethe loss formula at least as well as using the conventional approach. 
  Reference    (Z. Naturforsch. 31a, 75—79 [1976]; received December 6 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0075.pdf 
 Identifier    ZNA-1976-31a-0075 
 Volume    31 
10Author    F. Köksal, H. YiikselRequires cookie*
 Title    ESR of Paramagnetic Species Produced by Gamma Irradiation in Cadmium Oxalate Three Hydrate Single Crystal  
 Abstract    Paramagnetic species produced in a single crystal of cadmium oxalate three hydrate (CdC204-SHjO) by gamma irradiation have been investigated with the method of electron spin resonance. Only one radical species was observed at room temperature. Analysis of the experimental results leads to the conclusion that the species has the form RCHOH in which the unpaired electron is concentrated at the carbon atom and interacts with the two hydrogen atoms. The ESR pattern was observed nearly undiminished for more than three months after the irradiation. The g factor was found to be only very slightly anisotropic with an average value of 2.0124. The hyperfine inter-action tensors of the unpaired electron with the two H nuclei have been determined. 
  Reference    (Z. Naturforsch. 31a, 80—83 [1976]; received October 16 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0080.pdf 
 Identifier    ZNA-1976-31a-0080 
 Volume    31 
11Author    F. Fratev, H. Hermann, G. Olbrich, 0. E. Polansky, M. ZanderRequires cookie*
 Title    Höhere Triplettanregungszustände von Fluoren, Carbazol und Benzologen: CNDO-CI-Berechnungen und Triplett-Triplett-Absorptionsmessungen  
  Reference    (Z. Naturforsch. 31a, 84 [1976]; eingegangen am 2. Dezember 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0084.pdf 
 Identifier    ZNA-1976-31a-0084 
 Volume    31 
12Author    B. Gelbhaar, W. HanleRequires cookie*
 Title    Stöße zwischen Thalliumatomen im 6 2 D-Zustand und Molekülen  
 Abstract    Collisions between Excited Thallium 6-D Atoms and Molecules Energy transfer between the 6 2 D3/2 and 6 2 D5/2 energy levels of thallium, induced by TI —H2 and TI —N2 collisions have been investigated. The following cross sections for energy transfer Q (6 2 D3 2 —v 6 2 D5/2) and quenching Q (6 2 D3/2) have been determined: TI —H2: Q(6 2 D3/2—6 2 D5/2) = 87*10 —18 cm 2 ; Q(6 2 D5/2) = 43 • 10~ 18 cm 2 ; TI —N2: Q (6 2 D3/2 -> 6 2 D5/2) = 71 • 10 —16 cm 2 ; Q (6 2 D5/2) = 94 • 10 -16 cm 2 . 
  Reference    (Z. Naturforsch. 31a, 87 [1976]; eingegang am 20. Dezember 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0087.pdf 
 Identifier    ZNA-1976-31a-0087 
 Volume    31 
13Author    Peter Lamparter, Siegfried Steel, Walter Knoll, InstitutM V Laue, -P Langevin, GrenobleRequires cookie*
 Title    Struktur von Schmelzen aus dem System Wismut-Antimon mittels Neutronenbeugung  
 Abstract    Structure of Molten Bi-Sb-alloys by Means of Neutron Diffraction Neutron diffraction work (A = 0.695 Ä) was done with molten Bi-Sb-alloys in the temperature range between 550 and 750 °C. Furthermore molten Bi was investigated at 300 °C. The interference functions show subsidiary maxima especially for alloys with higher Sb-concentrations. Evaluation yields, that the melts contain two different kinds of structure: a) The one kind shows coordination number 9 and a statistical distribution of the atoms of two components. This kind is more inetal-like. b) The other kind shows coordination number 3, consists of non-centered tetrahedra with smaller nearest neighbour distance. It shows covalent binding. In molten Sb the nearest neighbour distance amounts up to 3.16 — 3.19 Ä for theo ne kind and up to 2.64 —2.78 Ä fort he other kind, which yields an mean distance of 2.99 Ä, which was ob-served. The dependence of the concentration of the statistical kind of meld, of the (Sb)4-, and the (Bi)4-kind from the concentration of the whole melt is given. By the model described the run of the measured mean coordination number and the mean distance versus concentration can be well explained. 
  Reference    (Z. Naturforsch. 31a, 90 [1976]; eingegangen am 6. Dezember 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0090.pdf 
 Identifier    ZNA-1976-31a-0090 
 Volume    31 
14Author    G. L. BordiertRequires cookie*
 Title    Precise Energies of K-Röntgen-Lines of Tm, Th, U and Pu  
 Abstract    The energies of the Kat-and Ka2-Röntgen lines of Tm, Th, U and Pu have been measured with high accuracy re-lative to the 411.794 keV y-line from a gold source. In ad-dition, the energies of a few Kß lines have been determined. 
  Reference    (Z. Naturforsch. 31a, 102—104 [1976]; received December 5 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0102_n.pdf 
 Identifier    ZNA-1976-31a-0102_n 
 Volume    31 
15Author    J. Kiessling, A. ScharmannRequires cookie*
 Title    Dipole Centres in Rare-Earth-Doped CaF,  
 Abstract    The reorientation of dipole centres in CaF2: RE 3+ (RE: Gd, Tb, Lu) is investigated by the method of ionic thermo-current (ITC). ITC peaks below 200 K are caused by re-orientation of RE 3+ -F~-complexes and related dipole centres, whereas peaks above 200 K seem to be of other origin. Both types of ITC peaks cannot be discriminated by polarization field strength dependence. 
  Reference    (Z. Naturforsch. 31a, 105—106 [1976]; received December 20 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0105_n.pdf 
 Identifier    ZNA-1976-31a-0105_n 
 Volume    31 
16Author    K. Behringer, P. ThomaRequires cookie*
 Title    Broad Structures in the VUV Argon Spectrum due to Merged A II Lines  
 Abstract    VUV spectra from argon arc experiments, performed at 1 atm and about 20 000 K, contain broad structures around 120 nm. These are shown to consist of merged A II lines from 7f —3d electronic transitions. 
  Reference    (Z. Naturforsch. 31a, 107—108 [1976]; received December 16 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0107_n.pdf 
 Identifier    ZNA-1976-31a-0107_n 
 Volume    31 
17Author    G. Dobrowolski, W. SchnabelRequires cookie*
 Title    Evidence for Preferential Polymer Solvation from Time-resolved Rayleigh Light Scattering Measurements  
 Abstract    In an acetone solution containing small portions of naph-thalene the latter is adsorbed preferentially to poly(methyl-methacrylate-co-phenylvinylketone). Evidence for preferential solvation is inferred from intrinsic viscosity data as well as from the halflife of the change of light scattering intensity after fragmentation of the macromolecules by a 25 ns flash of 347 nm light from a ruby laser. 
  Reference    (Z. Naturforsch. 31a, 109—110 [1976]; received December 6 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0109_n.pdf 
 Identifier    ZNA-1976-31a-0109_n 
 Volume    31 
18Author    FriedrichW. Hehl, G.David Kerlick, Paul Von Der HeydeRequires cookie*
 Title    On Hypermomentum in General Relativity I. The Notion of Hypermomentum  
 Abstract    In this series of notes, we introduce a new quantity into the theory of classical matter fields. Besides the usual energy-momentum tensor, we postulate the existence of a further dynamical attribute of matter, the 3rd rank tensor Aift of hypermomentum. Subsequently, a general rela-tivistic field theory of energy-momentum and hypermomentum is outlined. In Part I we motivate the need for hypermomentum. We split it into spin angular momentum, the dilatation hypermomentum, and traceless proper hypermomentum and discuss their physical meanings and conservation laws. 
  Reference    (Z. Naturforsch. 31a, 111—114 [1976]; received December 27 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0111.pdf 
 Identifier    ZNA-1976-31a-0111 
 Volume    31 
19Author    W. Waschkowski, L. KoesterRequires cookie*
 Title    Präzise Bestimmung von freien Wirkungsquerschnitten für Neutronen Precision Measurements of Free Cross Sections for Neutrons  
 Abstract    Rotating activation foils with resonance energies of 1.26 eV and 5.19 eV have been applied for exact measurements of neutron cross sections. The detector consisted of a sandwich of two rotating foils and was suitable for determining exactly the neutron flux at the resonance energy and energy changes in the neutron beam. The cross sections of polycrystalline samples showed uncertainties greater than the statistical error. The more accurate measurements on liquid samples yielded the following scattering cross sections of free atoms for neutrons of zero energy: 
  Reference    (Z. Naturforsch. 31a, 115—122 [1976]; eingegangen am 16. Dezember 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0115.pdf 
 Identifier    ZNA-1976-31a-0115 
 Volume    31 
20Author    K. DrägerRequires cookie*
 Title    Der effektive Spin als Modell zur Beschreibung von ESR- Hyperfeinspektren polykristalliner Systeme  
 Abstract    The Effective Spin as a Model to describe ESR-Hyperfine Spectra of poly cry stalline Samples Paramagnetic ions with hyperfine interaction generally have an involved ESR-spectrum. For host lattices of cubic symmetry it will be shown that while going from single crystals to powdered sys-tems the true spin quantum number S can be substituted by an effective spin quantum number S' = l/2. Using an isotropic spin Hamilton operator the energy-levels and their eigenfunctions as well as the transition probabilities are calculated explitely. The model is then applied to the ESR-spectrum of manganese-doped polycrystalline CaO. The theoretical spectrum fits the experimental up to 2-10 -5 and is in every respect comparable to results of the 3 rd order perturbation theory. Above all the model reproduces the true values for the (jr-factor and the hyperfine coupling constant A as known from single crystal investigations. This is also verified for Mn 2+ -ions on cubic sites of MgO and BaO. 
  Reference    (Z. Naturforsch. 31a, 123 [1976]; eingegangen am 20. Dezember 1975) 
  Published    1976 
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 TEI-XML for    default:Reihe_A/31/ZNA-1976-31a-0123.pdf 
 Identifier    ZNA-1976-31a-0123 
 Volume    31 
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