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1990 (227)
101Author    K. Kilimann, W. EbelingRequires cookie*
 Title    Energy Gap and Line Shifts for H-Like Ions in Dense Plasmas  
 Abstract    Based on the results of a foregoing paper (Z. Naturforsch. 44 a, 519 -523 (1989)) the density-depen-dence of the discrete energy states and the continuum level is calculated with better accuracy. A static approximation to the line shifts is derived and discussed. 
  Reference    Z. Naturforsch. 45a, 613—617 (1990); received October 311989 in revised version February 13 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0613.pdf 
 Identifier    ZNA-1990-45a-0613 
 Volume    45 
102Author    A. Bączyński, P. Targowski, B. Ziętek, D. RadomskaRequires cookie*
 Title    Fluorescence Spectra and Determination of the Energy of O-O Transitions of Coumarins in Liquid Solutions  
 Abstract    Analytical expressions of absorption and fluorescence spectra of some coumarins in ethyl alcohol at room temperature are given. Satisfactory agreement of measured and calculated spectra is obtained. It was possible to obtain the pure electronic transition energies immediately after excita-tion (from absorption spectra) and after the thermal and orientational equilibrium is reached (from fluorescence). An optical transition carries a dye-solvent system to a state in which the mutual interaction energy is larger than in the initial state. 
  Reference    Z. Naturforsch. 45a, 618—622 (1990); received September 29 1989 
  Published    1990 
  Keywords    Photoluminescence of solutions, Shapes of molecular spectra, Coumarins 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0618.pdf 
 Identifier    ZNA-1990-45a-0618 
 Volume    45 
103Author    Kazuo Igarashi, Mineo Kosaka, Masahiro Ikeda, Junichi MochinagaRequires cookie*
 Title    X-ray Diffraction Analysis of NdCl 3 Melt  
 Abstract    The structure of molten NdClj at 800 C C has been investigated by X-ray scattering and the correlation method. The nearest neighbor distance and coordination number of Nd-Cl are 2.77 Ä and 5.5 A, respectively. The Nd-Nd and CI-CI distances are 5.08 and 4.04 Ä, respectively. The average nearest neighbor distance and coordination number decrease markedly on melting, and the resulting short range structure of the melt is approximately octahedral. 
  Reference    Z. Naturforsch. 45a, 623—626 (1990); received December 14 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0623.pdf 
 Identifier    ZNA-1990-45a-0623 
 Volume    45 
104Author    S. Seehafer, P. Lamparter, S. SteebRequires cookie*
 Title    X-ray-and Neutron-diffraction Studies with Quasicrystalline and Amorphous Al-V-and Al-Mn-alloys  
 Abstract    Amorphous and quasicrystalline samples of Al 84 Mn 16 and A1 84 V 16 were produced by sputtering and melt-spinning, respectively. From X-ray and neutron-diffraction-results the total structure factors were evaluated. For amorphous as well as for quasicrystalline A1 84 V 16 the partial S A1 _ A1 -and S A1 _ v -structure factors were obtained, which yield the corresponding partial pair correlation func-tions, the atomic distances, and the partial coordination numbers. Also some information concern-ing the partial Bhatia-Thornton correlation functions could be obtained. Both the amorphous and the quasicrystalline Al-V-alloys show a linear expansion by a factor of 1.03 compared to the corresponding Al-Mn-alloy. The two amorphous alloys can be designed as isomorphous, whereas the quasicrystalline ones show pronounced deviations in the distance be-tween unequal atoms. The shortest atomic distance in amorphous A1 84 V 16 is 2.69 A, being,formed by Al-V-pairs with a coordination number 2. The nearest Al-Al-distance amounts to 2.84 A with a coordination number 8. The partial density-concentration correlation function clearly deviates from the hard sphere model. With the quasicrystalline specimens, the isomorphous substitution of Mn-and V-atoms is not perfect. The Al-V-correlation is split up, and this is not observed for the Al-Mn-correlation. Comparison of the amorphous and the corresponding quasicrystalline alloy shows some similarities. 
  Reference    Z. Naturforsch. 45a, 627—638 (1990); received January 20 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0627.pdf 
 Identifier    ZNA-1990-45a-0627 
 Volume    45 
105Author    Akhlesh Lakhtakia, VijayK. Varadan, VasundaraV. VaradanRequires cookie*
 Title    On Electromagnetic Fields in a Periodically Inhomogeneous Chiral Medium  
 Abstract    Electromagnetic fields in a periodically inhomogeneous chiral medium are examined. The con-stitutive properties of the chiral medium vary along the z axis, and reduced fields with prescribed x-variations are used. Coupled first-order differential equations are derived to describe the reduced fields. Two special cases -(i) piecewise constant inhomogeneity, and (ii) constant impedance inhomo-geneity, -are discussed in detail, and solution procedures are provided. 
  Reference    Z. Naturforsch. 45a, 639—644 (1990); received November 18 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0639.pdf 
 Identifier    ZNA-1990-45a-0639 
 Volume    45 
106Author    Ivan Gutman, Haruo HosoyaRequires cookie*
 Title    Molecular Graphs with Equal Z-Counting and Independence Polynomials  
 Abstract    It is demonstrated that the cycle graphs corresponding to the carbon atom skeletons of cyclo-alkanes and annulenes are the only graphs having the same Z-counting and independence poly-nomials. 
  Reference    Z. Naturforsch. 45a, 645—648 (1990); received November 6 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0645.pdf 
 Identifier    ZNA-1990-45a-0645 
 Volume    45 
107Author    R. WagenerRequires cookie*
 Title    Influence of Temperature on the Removal Rates of CH 2 (a ^j) by Inert Gases and Hydrocarbons  
 Abstract    The reactions of CH 2 (a 1 A 1) with the inert gases He, Ar, N 2 , with H 2 and with the hydrocarbon reactants CH 4 , C 2 H 6 , C 2 H 4 and C 6 H 6 have been investigated at 210, 295 and 475 K. CH 2 (ä 'AJ was generated by pulsed laser photolysis in a quasistatic thermostated gas cell and detected by pulsed laser induced fluorescence. Concentration profiles of CH 2 (ä were recorded under first order reaction conditions by varying the time delay between the photolysis and the probe laser pulses. The second order rate constants determined at room temperature are in good agreement with those of earlier work. No differences between the removal rates of ortho-and para-methylene nuclear spin states by the inert gases were observed. The experimental rate constants were fitted to an expression k = A -(77295 K) n . The results are given in the form {A ± A A} {n ± An) with A in units of 10 13 cm 3 /mol • s: 
  Reference    Z. Naturforsch. 45a, 649—656 (1990); received December 27 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0649.pdf 
 Identifier    ZNA-1990-45a-0649 
 Volume    45 
108Author    V. Tabakova, R. TrifonovaRequires cookie*
 Title    On the Shortwave Emission of Ga-activated Single Crystals of BaCl 2  
 Abstract    The luminescence of BaCl 2 -Ga single crystals at temperatures down to liquid helium under excitation with different energies is studied. The emission consists of several bands, the intensities of which depend on the temperature and the exciting energy. The excitation spectra of the different emission bands measured at 4 K, 78 K and 293 K are also reported. The results indicate the coexistence of centres of different structure and composition. The Jahn-Teller effect might also take place. 
  Reference    Z. Naturforsch. 45a, 657—660 (1990); received September 13 1989 
  Published    1990 
  Keywords    Luminescence, Barium chloride, Emission, Excitation 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0657.pdf 
 Identifier    ZNA-1990-45a-0657 
 Volume    45 
109Author    A. B. Vassilikou-Dova, G. LehmannRequires cookie*
 Title    Superposition-Model Analysis of NQR Data for NaAlCl 4  
 Abstract    The quadrupole splitting patterns for 23 Na and 27 A1 in NaAlCl 4 can very satisfactorily be reproduced by the distortions of their first coordination spheres, as shown by application of the superposition model. The same exponent of 7 for the dependence on bond lengths was used as previously found for NMR data of 9 Be, 23 Na, 25 Mg, 27 A1 and 29 Si with oxygen as ligand. The intrinsic splitting parameters are in the same range, perhaps a little larger than for oxygen as ligand. Small deviations between observed and calculated splitting patterns just outside the limits of error of the crystal structure data may be due to influences of the lattice, especially in the case of 27 A1, for which the distortions are fairly small. 
  Reference    Z. Naturforsch. 45a, 661—663 (1990); received January 16 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0661.pdf 
 Identifier    ZNA-1990-45a-0661 
 Volume    45 
110Author    Gerold Baier, Michael Klein, OttoE. RösslerRequires cookie*
 Title    Higher Tori in Volume-Preserving Maps  
 Abstract    A hierarchy of «-Tori is demonstrated numerically in volume-preserving (n + l)-dimensional in-vertible maps. 
  Reference    Z. Naturforsch. 45a, 664—668 (1990); received January 16 1990 
  Published    1990 
  Keywords    Volume-preserving maps, torus, hypertorus, attracting torus, chaos 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0664.pdf 
 Identifier    ZNA-1990-45a-0664 
 Volume    45 
111Author    H.-J Schulz, G. Roussos, S. W. BiernackiRequires cookie*
 Title    Optical Properties of Vanadium Ions in Zinc Sulphide  
 Abstract    The luminescence of synthetic ZnS: V crystals is studied at low temperatures (T % 4 K). The emission spectra comprise (i) a structured band centred around v = 5600 cm -1 , assigned to 3 T 2 (F) -> • 3 A 2 (F) transitions of substitutional V 3 + (3d 2) ions in a tetrahedral field, and (ii) a band around 4800 cm -assigned to 4 T 2 (F) -+ 4 Tj(F) transitions of V 2 + (3d 3) ions. In the range of the narrow no-phonon lines detected with both these emission bands, a temperature rise from 2 to 5 K entails a thermali-sation in the population of the spin-orbit multiplets forming the initial states of the corresponding transitions. A third emission band near 3800 cm 1 grows after annealing the crystals in Zn vapour. It is tentatively attributed to 5 E(D) -> 5 T 2 (D) transitions of V + (3d 4). A model of one-electron states represents donor-type as well as acceptor-type changes of the vanadium oxidation states, commenc-ing from V 2 + , the state with neutral effective charge. The model is substantially founded on the measured excitation spectra of the V 3+ and V 2+ emission bands, supplemented by transmission spectra. Besides the corresponding broad charge transfer bands, the spectra display a number of structures which are associated with excited states of the ions. These energy levels are approximated in a computation following the strong-field Tanabe-Sugano scheme but in addition allowing for different radial extensions of e-and t 2 -type wave functions. The method used also includes the possibility of fitting the free-ion levels. Various sets of numerical values are eventually obtained for the crystal-field splitting and the Racah parameters. Some of the levels involved are found to be subject to Jahn-Teller interaction. Key words: 71.55 F Impurity and defect levels (tetrahedrally bonded nonmetals); -71.70 Level splittings and interactions; -78.30 G Infrared spectra (nonmetallic inorganic crys-tals); -78.50 G Impurity absorption (semiconductors); -78.55 D Photolumines-cence (tetrahedrally bonded nonmetals). 
  Reference    Z. Naturforsch. 45a, 669—676 (1990); received January 11 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0669.pdf 
 Identifier    ZNA-1990-45a-0669 
 Volume    45 
112Author    H. J. Steinhoff, A. Redhardt, K. Lieutenant, W. Chrost, G. Hess, J. Schlitter, H. J. NeumannRequires cookie*
 Title    High Precision Measurements of the Permittivity of Water in the Microwave Range  
 Abstract    A practical version of a homodyne method for measuring the complex permittivity of high loss liquids at 3 and 9 GHz is described. The systematic errors are discussed in detail, because the homodyne method seems to be suitable as a simple standard method for precise measurements. The results of measurements on water in the temperature range 6 °C-45 °C are presented. The deter-mination of all five parameters of the Debye function is possible. Finally, accuracy limiting factors for the determination of the relaxation parameters are discussed in detail. 
  Reference    Z. Naturforsch. 45a, 677—686 (1990); received December 19 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0677.pdf 
 Identifier    ZNA-1990-45a-0677 
 Volume    45 
113Author    M. F. Holovko, YuV. Kalyuzhny, K. HeinzingerRequires cookie*
 Title    Electrostatic and Packing Contributions to the Structure of Water and Aqueous Electrolyte Solutions  
 Abstract    The role of electrostatic and packing contributions to the structure of water and aqueous elec-trolyte solutions has been investigated by the comparison of results of Molecular Dynamics simu-lations with those of analytical calculations for the corresponding Lennard-Jones systems. It is demonstrated that the electrostatic interactions play a dominant role in determining the characteristic data of the various radial distribution functions in the solutions, although their relative importance decreases with increasing pressure, temperature, and ionic concentration. It is proposed that for the analytical treatment of hydrogen bonded liquids the total potential should be subdivided into three regions -short range repulsion, potential minimum, long range electrostatic interactions -and a different theoretical approach should be employed for each region. 
  Reference    Z. Naturforsch. 45a, 687—694 (1990); received January 31 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0687.pdf 
 Identifier    ZNA-1990-45a-0687 
 Volume    45 
114Author    S. Wang, G. Li, H. Li, N. GetoffRequires cookie*
 Title    Characteristics of Photoelectrochemical Cells Based on n/n + -Si and p/n + -Si Photoanodes Modified by Metal Films  
 Abstract    Photoelectrochemical cells (PECs), composed of different epitaxial n-Si photoanodes coated with evaporated metal film of Ni, Pt, Ni/Pt and immersed in solution with redox couple Br 2 /Br -or Fe(NC)g~7Fe(CN)£~ were investigated. The open circuit photovoltage and short circuit current density of these PECs under optimum conditions by illuminating with a bromine-tungsten lamp (65 mW/cm 2), are 0.494 V and 45.8 mA/cm 2 , respectively. By using a p/n + junction for the epitaxial silicon and the Schottky barrier effect formed at the silicon-metal interface, a much higher conversion efficiency of optical to electrical energy up to 12.3% could be achieved. 
  Reference    Z. Naturforsch. 45a, 695—701 (1990); received January 26 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0695.pdf 
 Identifier    ZNA-1990-45a-0695 
 Volume    45 
115Author    W. Neustock, A. Guarnieri, J. Demaison, G. WlodarczakRequires cookie*
 Title    The Millimeter and Submillimeter-Wave Spectrum of Dimethylether  
 Abstract    We report the analysis of the rotational spectrum of dimethylether measured between 60 and 400 GHz. Rotational and quartic centrifugal distortion constants are given. Internal rotation split-tings are analysed with the I AM method. The value of is compared to the values obtained for similar molecules. 
  Reference    Z. Naturforsch. 45a, 702—706 (1990); received January 21 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0702.pdf 
 Identifier    ZNA-1990-45a-0702 
 Volume    45 
116Author    B. VogelsangerRequires cookie*
 Title    Triple Resonance Experiments in Microwave Fourier Transform Spectroscopy  
 Abstract    Two-dimensional (2 D) correlation techniques in microwave Fourier transform spectroscopy have been extended to study triple resonance phenomena. Dipole-forbidden double-and triple-quantum transitions have been observed with a five-pulse sequence. The introduction of a phase cycle acting as a triple-quantum filter has simplified the recorded spectra. Experimental results on trifluo-romethylacetylene are given as an example. 
  Reference    Z. Naturforsch. 45a, 707—710 (1990); received December 20 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0707.pdf 
 Identifier    ZNA-1990-45a-0707 
 Volume    45 
117Author    Ch Keussen, R. Schwarz, U. Andresen, H. DreizlerRequires cookie*
 Title    Improved Version of a Microwave Fourier Transform Spectrometer in the Frequency Band from 26 to 40 GHz  
 Abstract    We report the design and performance of an improved version of a microwave Fourier transform spectrometer in the frequency region between 26 and 40 GHz for the investigation of rotational spectra. The performance is illustrated by rotational transitions of allene-d 4 and isotopomers of carbonyl sulfide in natural abundance. The high sensitivity of the spectrometer allows the measure-ment of very weak lines in only a few minutes. 
  Reference    Z. Naturforsch. 45a, 711—714 (1990); received December 22 1989 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0711.pdf 
 Identifier    ZNA-1990-45a-0711 
 Volume    45 
118Author    Joachim Gripp, Helmut DreizlerRequires cookie*
 Title    The Microwave Spectrum of Isopropyl Iodide: The Iodine Hyperfine Structure and a Centrifugal Distortion Analysis  
 Abstract    The ground sta f e microwave spectrum of isopropyl iodide has been investigated by microwave Fourier transform (MWFT) spectroscopy. 212 hyperfine components of 39 mainly a-type transitions have been assigned from the measured spectra in the frequency range between 4 and 30 GHz. With a MWFT double resonance modulation (MWFTDR) spectrometer a weak c-type transition and a "forbidden" AJ = 2 line could be observed. The spectra were analysed using a diagonalization procedure of the complete Hamiltonian matrix and a simultaneous least squares fit of the rotational, quartic centrifugal distortion and the iodine quadrupole and spin rotation coupling constants directly to the measured frequencies. A set of 14 constants could be obtained with high accuracy. The rotational constant A and some of the centrifugal distortion constants could be improved using some large higher order quadrupole perturbations and the results of the MWFTDR measurements for the analysis. 
  Reference    Z. Naturforsch. 45a, 715—723 (1990); received January 31 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0715.pdf 
 Identifier    ZNA-1990-45a-0715 
 Volume    45 
119Author    M. Krüger, H. DreizlerRequires cookie*
 Title    A Microwave Fourier Transform Spectrometer with a Single Microwave Source  
 Abstract    Design and performance of a microwave Fourier transform spectrometer in the frequency region around 8 GHz are reported. Operation and experimental set-up are simplified compared to previous designs. 
  Reference    Z. Naturforsch. 45a, 724—726 (1990); received January 31 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0724.pdf 
 Identifier    ZNA-1990-45a-0724 
 Volume    45 
120Author    JohnC. Fetzer, Maximilian ZanderRequires cookie*
 Title    Fluorescence, Phosphorescence, and E-Type Delayed Fluorescence of Hexabenzo [bc,ef,hi,kl,no,qr] coronene  
 Abstract    The luminescence of hexabenzo [be,ef,hi,kl,no,qr] coronene (I) has been studied in a perhydro-coronene matrix at temperatures from 77 to 353 K. I exhibits phosphorescence and prompt and E-type delayed fluorescence. The phosphorescence transition is symmetry-forbidden. The lumines-cence behaviour of I is closely related to that of coronene (II). 
  Reference    Z. Naturforsch. 45a, 727—729 (1990); received February 24 1990 
  Published    1990 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0727.pdf 
 Identifier    ZNA-1990-45a-0727 
 Volume    45 
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