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1992[X]
121Author    M. Gnirßt, F. WahlRequires cookie*
 Title    A Microscopic Theory of a Single Hydrogen Centre in a Magnesium Crystal  
 Abstract    A microscopic theory of a single hydrogen center embedded in a magnesium crystal is presented. Starting with a many-particle Schrödinger equation, an adiabatic decoupling yields in an electronic system a protonic system and a host lattice system. The storage energy is defined to consist of an electronic part and lattice contributions. The electronic problem is treated with the help of a special energy difference procedure developed by Wahl et al. This procedure is applied in a higher approx-imation to calculate the electronic energy difference eigenvalue between a metal crystal with and without a hydrogen impurity. The lattice problem is treated in the classical harmonic approxima-tion. 
  Reference    Z. Naturforsch. 47a, 733—747 (1992); received February 17 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0733.pdf 
 Identifier    ZNA-1992-47a-0733 
 Volume    47 
122Author    A. Harfoush, S. Sh, SoulaymanRequires cookie*
 Title    Presparking Effect in Spark Source Mass Spectrometry  
 Abstract    The Relative Sensitivity Factor (RSF) in Spark Source Mass Spectrometry analysis was found to be dependent on the number and duration of previous sparking periods. This dependency becomes very strong when dealing with volatile elements. By statistical analysis of experimental RSF values it was found that there is a linear correlation between In (RSF) of some trace elements and their boiling temperature. This correlation fails when dealing with volatile elements and carbon. It was found that elements with a large diffusion coefficient have a large RSF. 
  Reference    Z. Naturforsch. 47a, 748—752 (1992); received September 12 1989 
  Published    1992 
  Keywords    Relative Sensitivity Factor, Spark Source Mass Spectrometry, Presparking effect, Boiling temperature, Diffusion 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0748.pdf 
 Identifier    ZNA-1992-47a-0748 
 Volume    47 
123Author    S. Sh, SoulaymanRequires cookie*
 Title    Theoretical Melting Curves of Alkali Halides  
 Abstract    An analysis of the melting curves of alkali halides is given. The study is based on the Improved Unsymmetrized Self-Consistent Field Method (IUSCFM) for strongly anharmonic crystals with complex lattice and the energy, entropy and Ross's criterions in calculating the melting curves of alkali halides. The anharmonicities up to sixth order have been taken into consideration. The energy criterion was proven to be the most correct one along the melting curves of the high pressure modification (CsCl structure) while the entropy and Ross's criterions lead to a little better agreement with experiment than the energy criterion when dealing with rocksalt structure. Calculations of the melting curves of KCl and CsCl are compared with the experimental results. 
  Reference    Z. Naturforsch. 47a, 753—760 (1992); received January 20 1992 
  Published    1992 
  Keywords    Alkali halides, Melting curves, Energy criterion, Entropy criterion, Ross's criterion 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0753.pdf 
 Identifier    ZNA-1992-47a-0753 
 Volume    47 
124Author    J. L. Alonso, N. Heineking, H. Dreizler, A. G. Lesarri, J. C. LópezRequires cookie*
 Title    Determination of a High Potential Barrier Hindering Internal Rotation in 2-Methylcyclopentanone and a-Methyl-y-Butyrolactone by Microwave Fourier Transform Spectroscopy  
 Abstract    The microwave spectra of a-methyl-y-butyrolactone and 2-methylcyclopentanone have been reinvestigated using microwave Fourier transform spectroscopy. A-E splittings due to internal rotation of the methyl group have been observed in the ground and several vibrationally excited states for both molecules. From an internal-axis-method analysis of these splittings, values of the methyl group internal rotation barrier of 2.61 kcal mol -1 for a-methyl-y-butyrolactone and 2.41 kcal mol -1 for 2-methylcyclopentanone have been obtained. 
  Reference    Z. Naturforsch. 47a, 761—764 (1992); received March 28 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0761.pdf 
 Identifier    ZNA-1992-47a-0761 
 Volume    47 
125Author    K. Indira, M. K. Rudra Warier, T. R. Ananthakrishnan, C. M. PaulRequires cookie*
 Title    Dependence of Potential Energy on Inter-bond Angles in Simple Molecules  
 Abstract    A method is developed to investigate the variation of potential energy contributions (F stretch , F bend , ^stretch-bend an d Ktretch-stretch) > n simple molecules when their inter-bond angles 6 are varied arbitrarily. Applied to XY 2 bend symmetric systems, the V— 6 plots suggest that the actual equilibrium con-figuration in these molecules lies in the premises of minimum F bend and zero F stretch . bend . 
  Reference    Z. Naturforsch. 47a, 765—767 (1992); received February 29 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0765.pdf 
 Identifier    ZNA-1992-47a-0765 
 Volume    47 
126Author    NohaM. Yahya, SalimM. KhalilRequires cookie*
 Title    A Theoretical Study of Monosubstituted Cyclopropenyl System  
 Abstract    MONDO-Forces calculations have been performed, with complete optimization of geometry on X-cyclopropenyl system (cations, radicals and anions), where X is H, O", OH, CH 3 , CN, N0 2 , F and CF 3 . All substituents prefer planar structure when substituted on both cations and radicals, while they prefer pyramidal structure in the case of anions except CF 3 . The substituents O", OH and F act as electron releasing, while CHO, N0 2 and CF 3 act as electron withdrawing when substituted on cyclopropenyl system. CH 3 and CN show amphielectronic behaviour. They act as electron releasing on the cations and withdrawing on both radicals and anions depending on electron demand. In the case of cations and radicals, all substituents were found to increase the vicinal bonds and decrease the distal bonds and bond angles to which the substituent is attached. For anions the substitutents show no such regularity because the substituents are out of the three-membered ring plane. All substituents increase the stability of the cyclopropenyl system except CF 3 in the case of the cation. 
  Reference    Z. Naturforsch. 47a, 768—774 (1992); received November 30 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0768.pdf 
 Identifier    ZNA-1992-47a-0768 
 Volume    47 
127Author    GhazwanF. FadhilRequires cookie*
 Title    Factor Analysis of Long Range Substituent Effects on C-13 NMR Chemical Shifts and Target Factor Testing of Different Types of Substituent Parameters  
 Abstract    A factor analysis technique has been used to analyse 186 long range C-13 substituent chemical shift (scs) of 90 compounds of the general formula X-G-Y; X represents the set of substituents, G is a hydrocarbon skeleton, in some cases unsaturated (phenylene) and in other cases saturated. Y consists of a variety of groups which contain the probe site. The data were taken from the literature. Although they were measured in different laboratories, the solvent was CDC1 3 in every case. From the value of the factor indicator function (IND) it was concluded that two factors were significant. The validity of several empirical and theoretical sub-stituent parameters has been investigated by Target testing. Models were constructed for the sub-stituent effect. Results from Target factor testing, model designing and linear regression analysis have shown that Reynolds' er£ and <r F are the best substituent parameters in reproducing the C-13 substituent chemical shift. 
  Reference    Z. Naturforsch. 47a, 775—780 (1992); received December 10 1991 
  Published    1992 
  Keywords    C-13 nmr, Substituent effect, Factor analysis, Target factor testing 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0775.pdf 
 Identifier    ZNA-1992-47a-0775 
 Volume    47 
128Author    Isao Okada, Kazunori IchiokaRequires cookie*
 Title    Internal Cation Mobilities in Molten (Li, Ag)N0 3 and (K,Ag)NO a Remeasured by the Klemm Method  
 Abstract    Internal mobility ratios b Li /b As and b K /b Ag in molten (Li,Ag)N0 3 and (K,Ag)N0 3 have been measured by Klemm's countercurrent electromigration method. From these and available data on the densities and conductivities the internal mobilities have been calculated. The present experiments yielded more accurate data than previous ones using other methods. Over the investigated range of concentration and temperature, b Ag is greater than b u or b K . The results are discussed together with earlier ones obtained for (Na, Ag)N0 3 . 
  Reference    Z. Naturforsch. 47a, 781—787 (1992); received January 21 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0781.pdf 
 Identifier    ZNA-1992-47a-0781 
 Volume    47 
129Author    Yoshihiro Kubozono, Masafumi Ata, Yasunobu Suzuki, Yasuhiko Gondo, Masaru ShiotaniRequires cookie*
 Title    ESR Spectra of Para-Substituted Alkyl-and Alkenylbenzene Radical Cations in Halocarbon Matrices  
 Abstract    The ESR spectra of several para-substituted alkyl-and alkenylbenzene radical cations generated by 60 Co y-ray irradiation in halocarbon matrices at 77 K have been studied with the aid of semiem-pirical MO calculations. It has been found that the ethyl conformation of 1,4-diethylbenzene radical cation (1,4-DEB +) in CC1 2 FCC1F 2 is largely different from that in CC1 3 CF 3 . Further the ethyl and n-propyl groups in 4-ethyltoluene and 4-n-propyltoluene radical cations in CC1 2 FCC1F 2 take differ-ent conformations from that of l,4-DEB + \ The conformations of the alkylbenzene radical cations depend strongly both on the matrices and on the substituent groups. A peculiar radiolytical reaction of 1,4-diisopropylbenzene to a deprotonation-type neutral radical in CC1 2 FCC1F 2 has been found, similarly to the case of photolysis. 
  Reference    Z. Naturforsch. 47a, 788—796 (1992); received September 3 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0788.pdf 
 Identifier    ZNA-1992-47a-0788 
 Volume    47 
130Author    P. Fischer, H. Port, H. C. WolfRequires cookie*
 Title    Zeitaufgelöstes Fluoreszenz-Löschen in ultradünnen Coronen-Schichten auf Silizium-Substraten  
 Abstract    The fluorescence decay from thin coronene films deposited on Si (100) and Si/Si0 2 substrates are measured as a function of coronene coverage at helium temperature. As the film thickness is decreased (1000 Ä-10 Ä) the decays are shortened and increasingly deviate from monoexponential. Excellent fits to the experimental curves are achieved by superimposing the monoexponential decay by an empirical function of the Kohlrausch type. Possible quenching processes are modeled in terms of energy transport through the layer followed by trapping in surface states and direct energy transfer from the excited molecules to the substrate. 
  Reference    Z. Naturforsch. 47a, 797—802 (1992); received June 8 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0797.pdf 
 Identifier    ZNA-1992-47a-0797 
 Volume    47 
131Author    J. Wąsicki, M. Grottel, A. Kozak, Z. PająkRequires cookie*
 Title    An Effect of Deuteration on Ion Motions and Hydrogen Bondings in Guanidinium Tetrafluoroborate  
 Abstract    The fluorine spin-lattice relaxation time as well as NMR second moment for perdeuterated guanidinium tetrafluoroborate were studied over a wide range of temperature. An analytical solution of a set of coupled differential equations describing the time variation of nuclear magnetisations for four unlike spin systems was applied to analyse all cross-relaxation effects in the compound. Activation parameters £ a F = 19.3 kJ/mole and = 9 • 10" 14 s for the isotropic anion reorientation were derived. A coupling of rotational modes of cation and anion was found. Significant lowering of the melting point explained by a weakening of the hydrogen bonds involves diminishing of the ion activation energies due to the large positive isotope effect. 
  Reference    Z. Naturforsch. 47a, 803—806 (1992); received April 9 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0803.pdf 
 Identifier    ZNA-1992-47a-0803 
 Volume    47 
132Author    Eryk WolarzRequires cookie*
 Title    Determination of some Dye Parameters by Polarized Fluorescence Spectroscopy  
 Abstract    A method of determining the angles between the emission and absorption dipole moments and the molecular symmetry axis is described. The order parameters <P 2 > and of nematic-dye mixtures are also calculated. The method is applied in investigations of tricarboxylic acid derivatives dissolved in the nematic mixture E 18 (Merck). 
  Reference    Z. Naturforsch. 47a, 807—812 (1992); received December 28 1991 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0807.pdf 
 Identifier    ZNA-1992-47a-0807 
 Volume    47 
133Author    A.Venkata Subbaiah, J.Lakshmana Rao, R. Murali, Krishna, S.V J LakshmanRequires cookie*
 Title    Absorption Spectrum of Ni(II) Ions Doped in Magnesium Thallium Sulphate Hexahydrate  
 Abstract    The optical absorption spectrum of Ni(II) ions doped in magnesium thallium sulphate hexa-hydrate has been studied at room-and liquid nitrogen-temperature. The crystal shows characteristic absorption of Ni(II) ion in the visible and near infrared region. The observed bands are assigned as transitions from the ground state 3 A2 g (F) to various excited triplet and singlet levels of the Ni(II) ion in octahedral symmetry. The splitting in one of the bands at liquid nitrogen temperature has been explained to be due to spin-orbit splitting. All the observed band positions have been fitted with the parameters B, C, Dq, and 
  Reference    Z. Naturforsch. 47a, 813—818 (1992); received April 13 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0813.pdf 
 Identifier    ZNA-1992-47a-0813 
 Volume    47 
134Author    R. Stoop, J. ParisiRequires cookie*
 Title    Phase Transitions of Scaling Functions Derived from Experimental Time Series  
 Abstract    The occurrence of phase transitions in dynamical systems is intimately related to the analyticity properties of the thermodynamical functions. Such effects are believed to be of generic nature (for example, homoclinic tangency points). For one-dimensional maps, their existence has been proven for both the probabilistic and the dynamical scaling functions (that is, the / (a) and <P (A) spectra, respectively). With the help of simple model systems, we elucidate the different combinations in which the two types of phase transitions (namely, in the / (a) and <P (2) spectra) can appear. More-over, we demonstrate the numerical evidence of phase-transition-like behavior in both spectra derived from experimental time series of laser and semiconductor systems. Finally, we discuss new aspects for the evaluation of the thermodynamic functions from time series. 
  Reference    Z. Naturforsch. 47a, 819—825 (1992); received April 21 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0819.pdf 
 Identifier    ZNA-1992-47a-0819 
 Volume    47 
135Author    H. Uhlig, L. Rohr, H.-J Güntherodt, P. Fischer, P. Lamparter, S. SteebRequires cookie*
 Title    Short Range Structure of Amorphous Ni 50 Ta 50 -Alloys by Means of X-Ray-and Neutron-Diffraction  
 Abstract    Amorphous Ni 50 Ta 50 -samples with their high crystallization temperature of 985 K were investigated. To evaluate the three partial structure factors of amorphous Ni 50 Ta 50 one X-ray diffraction experiment was performed with Ni 50 Ta 50 and two neutron diffraction experiments with Co 10 Ni 40 Ta 50 and with Ni 50 Ta 50 , respectively. The Bhatia-Thornton partial structure factor S CC (Q) indicates rather strong chemical short range order which also explains the premaximum observed in the Faber-Ziman partial S NiNi (Q)-function. The nearest neighbor distance is 2.82 Ä for Ni-Ni, 2.91 Ä for Ta-Ta, and is shortest for Ni-Ta, 2.44 Ä. The coordination numbers are iV NiNi = 4.9, N TaTa = 8.2, and N NiTa = 6.0. We report on the chemical short range order and the possible binding behavior in a-Ni S0 Ta 50 and compare the present results with those reported in the literature on a-Ni 40 Ti 60 as well as on a-Ni 55 Ta 45 . 
  Reference    Z. Naturforsch. 47a, 826—832 (1992); received May 7 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0826.pdf 
 Identifier    ZNA-1992-47a-0826 
 Volume    47 
136Author    Walter Hoyer, Hartmut Neumann, Manfred WobstRequires cookie*
 Title    Structure Investigation on Liquid Tellurium by X-Ray and Neutron Scattering  
 Abstract    We present the results of neutron and X-ray scattering experiments on liquid tellurium. No dependence on temperature of the radius and the coordination number of the first neighbour shell has been found in the temperature range between 460 °C and 550 °C. We investigate the influence of the truncation of the Fourier transformation on the determined coordination number of nearest neighbours and on the shape of the second coordination maximum at both, the lower and upper integration limit. The structure of liquid tellurium can be described in terms of a chain-like atomic arrangement with two bonds per atom. 
  Reference    Z. Naturforsch. 47a, 833—840 (1992); received May 8 1992 
  Published    1992 
  Keywords    Neutron scattering, X-ray scattering, Short-range order, Liquid tellurium, Termination effect 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0833.pdf 
 Identifier    ZNA-1992-47a-0833 
 Volume    47 
137Author    Toshiyuki Takamuku, Kazumasa Yoshikai, Toshio Yamaguchi, Hisanobu WakitaRequires cookie*
 Title    Structure of Supercooled Aqueous Zinc(II) Bromide Solutions by Raman and X-Ray Scattering Methods  
 Abstract    The structure of aqueous zinc(II) bromide solutions with [H 2 0]/[ZnBr 2 ] molar ratios 5 and 10 in the supercooled state and at ambient temperature has been investigated by Raman spectroscopy and X-ray scattering. Raman spectra of glassy solutions have also been measured for comparison. The Raman and X-ray data suggest that tetrabromo and hexaaqua zinc(II) complexes are favoured in the supercooled and glassy state, while dibromo-and tribromozinc(II) complexes are formed as main species in the solutions at ambient temperature. Probably the reactions 2 [ZnBr 2 (OH 2)] + 2H 2 0 [ZnBr 4 ] 2 ~ + [Zn(OH 2) 6 ] 2 + 4[ZnBr 3 (OH 2)]~ + 2H 2 0 -> 3[ZnBr 4 ] 2 ~ + [Zn(OH 2) 6 ] 2 + occur in the supercooled and glassy solutions. These equilibrium shifts are discussed. 
  Reference    Z. Naturforsch. 47a, 841—848 (1992); received April 24 1992 
  Published    1992 
  Keywords    Supercooled solution, Zinc(II) bromide, Raman spectroscopy, X-ray diffraction, Structure 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0841.pdf 
 Identifier    ZNA-1992-47a-0841 
 Volume    47 
138Author    T. Böttjer, G. Lehmann, M. StockhausenRequires cookie*
 Title    An Electron Paramagnetic Resonance Study of Mn 2 + Ions Doped in Langbeinites  
 Abstract    The cubic (high temperature) phase of some langbeinites, A 2 B 2 + (S0 4) 3 with 11 different combi-nations of A and B type cations, doped with Mn 2+ , is investigated by EPR. Powder or single crystal spectra are measured at X-band. They indicate centers of axial symmetry in all cases. In 6 of the langbeinites two centers are found which differ considerably in intensity. Both centers are substitu-tional defects (Mn in the crystallographically nonequivalent divalent B ion sites). For the more intense one the zero field splitting parameter is proved to be negative in all cases. That center is assigned to the more spacious site which, depending on the cation size, allows for local relaxation. It is shown by comparison with predictions of the superposition model that relaxation appears to be effective. 
  Reference    Z. Naturforsch. 47a, 849—856 (1992); received April 27 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0849.pdf 
 Identifier    ZNA-1992-47a-0849 
 Volume    47 
139Author    R. Ludwig, D. S. Gill, M. D. ZeidlerRequires cookie*
 Title    Molecular Reorientation of Methanol in Mixtures with Carbon Tetrachloride  
 Abstract    Proton and oxygen-17 nmr relaxation rates of CD 3 17 OH as well as deuteron nmr relaxation rates of CH 3 OD were measured in mixtures with carbon tetrachloride at different compositions and temperatures. By varying the 17 0-content different contributions to the proton relaxation rate could be separated and from the 17 0-H dipolar interaction contribution the correlation time of the OH bond was determined. Using these correlation times the composition dependence of the deu-terium and oxygen-17 quadrupole coupling constants of methanol was derived. A strong variation of the coupling constants over the measured composition range is evident. 
  Reference    Z. Naturforsch. 47a, 857—864 (1992); received April 27 1992 
  Published    1992 
  Keywords    Relaxation rates, Correlation time, Deuteron quadrupole coupling constant, Oxygen-17 quadrupole coupling constant, Methanol + Carbon tetrachloride mixtures 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0857.pdf 
 Identifier    ZNA-1992-47a-0857 
 Volume    47 
140Author    Michael Krüger, Helmut DreizlerRequires cookie*
 Title    The Microwave Spectra and Nitrogen Quadrupole Coupling Constants of Cyano-and Isocyano-pentafluorobenzene  
 Abstract    The microwave spectra of cyano-pentafluorobenzene, C 6 F 5 CN, and isocyano-pentafluoro-benzene, C^NC, have been assigned by molecular beam microwave Fourier transform spectros-copy. The N nuclear quadrupole coupling constants have been determined for both isomers. 
  Reference    Z. Naturforsch. 47a, 865—868 (1992); received May 23 1992 
  Published    1992 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0865.pdf 
 Identifier    ZNA-1992-47a-0865 
 Volume    47 
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