| | 101 | Author
| K. Kilimann, W. Ebeling | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0613.pdf | | | | Identifier
| ZNA-1990-45a-0613 | | | | Volume
| 45 | |
| 103 | Author
| Kazuo Igarashi, Mineo Kosaka, Masahiro Ikeda, Junichi Mochinaga | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0623.pdf | | | | Identifier
| ZNA-1990-45a-0623 | | | | Volume
| 45 | |
| 104 | Author
| S. Seehafer, P. Lamparter, S. Steeb | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0627.pdf | | | | Identifier
| ZNA-1990-45a-0627 | | | | Volume
| 45 | |
| 105 | Author
| Akhlesh Lakhtakia, VijayK. Varadan, VasundaraV. Varadan | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0639.pdf | | | | Identifier
| ZNA-1990-45a-0639 | | | | Volume
| 45 | |
| 107 | Author
| R. Wagener | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0649.pdf | | | | Identifier
| ZNA-1990-45a-0649 | | | | Volume
| 45 | |
| 108 | Author
| V. Tabakova, R. Trifonova | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0657.pdf | | | | Identifier
| ZNA-1990-45a-0657 | | | | Volume
| 45 | |
| 109 | Author
| A. B. Vassilikou-Dova, G. Lehmann | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0661.pdf | | | | Identifier
| ZNA-1990-45a-0661 | | | | Volume
| 45 | |
| 111 | Author
| H.-J Schulz, G. Roussos, S. W. Biernacki | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0669.pdf | | | | Identifier
| ZNA-1990-45a-0669 | | | | Volume
| 45 | |
| 112 | Author
| H. J. Steinhoff, A. Redhardt, K. Lieutenant, W. Chrost, G. Hess, J. Schlitter, H. J. Neumann | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0677.pdf | | | | Identifier
| ZNA-1990-45a-0677 | | | | Volume
| 45 | |
| 113 | Author
| M. F. Holovko, YuV. Kalyuzhny, K. Heinzinger | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0687.pdf | | | | Identifier
| ZNA-1990-45a-0687 | | | | Volume
| 45 | |
| 114 | Author
| S. Wang, G. Li, H. Li, N. Getoff | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0695.pdf | | | | Identifier
| ZNA-1990-45a-0695 | | | | Volume
| 45 | |
| 115 | Author
| W. Neustock, A. Guarnieri, J. Demaison, G. Wlodarczak | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0702.pdf | | | | Identifier
| ZNA-1990-45a-0702 | | | | Volume
| 45 | |
| 116 | Author
| B. Vogelsanger | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0707.pdf | | | | Identifier
| ZNA-1990-45a-0707 | | | | Volume
| 45 | |
| 117 | Author
| Ch Keussen, R. Schwarz, U. Andresen, H. Dreizler | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0711.pdf | | | | Identifier
| ZNA-1990-45a-0711 | | | | Volume
| 45 | |
| 118 | Author
| Joachim Gripp, Helmut Dreizler | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0715.pdf | | | | Identifier
| ZNA-1990-45a-0715 | | | | Volume
| 45 | |
| 120 | Author
| JohnC. Fetzer, Maximilian Zander | Requires 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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| default:Reihe_A/45/ZNA-1990-45a-0727.pdf | | | | Identifier
| ZNA-1990-45a-0727 | | | | Volume
| 45 | |
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