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Facet   Publication Year 1992  [X]
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1992[X]
161Author    M. Bentaiba, L. Chetouani, T. F. HammannRequires cookie*
 Title    Feynman-Kleinert's Treatment of a Class of Harmonic-Oscillators  
 Abstract    The Feynman-Kleinert method is applied to the harmonic oscillator class of potentials obtained through the factorization method. It is found that the free energy is in good agreement with the exact energy of the harmonic oscillator 
  Reference    Z. Naturforsch. 47a, 1013—1016 (1992); received June 26 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1013 
 Volume    47 
162Author    A. Kawski, A. Kubicki, B. Kukliński, I. Gryczyński, Z. GryczyńskiRequires cookie*
 Title    Isomerization of Diphenyl Polyenes. Part II. Fluorescence Properties of l,8-Diphenyl-l,3>5,7-octatetraene in Poly (vinyl alcohol) Film  
 Abstract    The effect of temperature on the fluorescence properties of l,8-diphenyl-l,3,5,7-octatetraene (DPO) in polyvinyl alcohol) film (PVA) was investigated in the range from 295 to 428 K. Upon heating above 353 K, the quantum yield of DPO increases rapidly. This effect is irreversible, similarly as the optical density in the long wavelength absorption band (320-440 nm). It has its origin in the cis-trans conversion of DPO molecules in PVA film at high temperatures. The behaviour of the fluorescence anisotropy in the same temperature range was also investigated. The emission an-isotropy was found to be a viscosity indicator in the microenvironment of the DPO molecules in PVA film. 
  Reference    Z. Naturforsch. 47a, 1017—1022 (1992); received July 13 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1017 
 Volume    47 
163Author    Eiichiro Matsubara, Kaneharu Okuda, Yoshio Waseda, Toshihiko SaitoRequires cookie*
 Title    Surface Structure of Nanometer-Sized Zinc Ferrite Particles by the Anomalous X-ray Scattering (AXS) Method  
 Abstract    The atomic structure of nanometer-sized zinc ferrite particles has been studied with the anomalous x-ray scattering (AXS) method as well as the ordinary x-ray diffraction. The analysis of the peak broadening indicated that little microstrain exists in these nanometer-sized particles, and the average size of the particles is estimated to be 4 nm. Since the ratio of atoms located on the surface increases extremely in such fine particles, the contribution of these surface atoms to the x-ray scattering intensity was evaluated. The interference function Q ; (0) for the surface atoms appears to be similar to that of the zinc-ferrite glass. The experimental intensity is successfully explained by using a simple particle model consisting of the about 0.2 nm thick surface layer having a glass-like structure and the internal atoms having the ferrite crystalline structure. 
  Reference    Z. Naturforsch. 47a, 1023—1028 (1992); received July 17 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1023 
 Volume    47 
164Author    C. T. Yap, Younan HuaRequires cookie*
 Title    Principal Component Analysis of Chinese Porcelains from the Five Dynasties to the Qing Dynasty  
 Abstract    This is a study of the possibility of identifying antique Chinese porcelains according to the period or dynasty, using major and minor chemical components (Si0 2 , A1 2 0 3 , Fe 2 0 3 , K 2 Ö, Na 2 0, CaO and MgO) from the body of the porcelain. Principal component analysis is applied to published data on 66 pieces of Chinese procelains made in Jingdezhen during the Five Dynasties and the Song, Yuan, Ming and Qing Dynasties. It is shown that porcelains made during the Five Dynasties and the Yuan (or Ming) and Qing Dynasties can be segregated completely without any overlap. However, there is appreciable overlap between the Five Dynasties and the Song Dynasty, some overlap between the Song and Ming Dynasties and also between the Yuan and Ming Dynasties. Interest-ingly, Qing procelains are well separated from all the others. The percentage of silica in the porcelain body decreases and that of alumina increases with recentness with the exception of the Yuan and Ming Dynasties, where this trend is reversed. 
  Reference    Z. Naturforsch. 47a, 1029—1033 (1992); received July 14 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1029 
 Volume    47 
165Author    B. A. Bilal, E. MüllerRequires cookie*
 Title    Potentiometrie Study of Magnesium Fluoro Complexes in Aqueous Solutions up to 473 K and 1 kbar  
 Abstract    The formation of magnesium fluoro complexes in a hydrothermal fluorite-bearing model solution has been potentiometrically studied up to 473 K and 1 kbar at the ionic strength I = 1 m (NaCl), in order to estimate the competition with the formation of the lanthanide fluoro and fluorohydroxo complexes in such systems. No evidence of difluoro complex was found at p, T, [F -] and pH conditions which are relevant to fluorite formation. The apparent formation constant Q, as well as the apparent thermodynamic data AG, AS and AH of MgF + have been determined. The effect of pressure was found to be negligible. The competition with the lanthanide complexes becomes increasingly negligible with increasing T and in particular with increasing pH. Key words: Formation of MgF + in hydrothermal fluorite-bearing solutions; Apparent thermody-namic data of MgF + at high p and T; Potentiometrie study. 
  Reference    Z. Naturforsch. 47a, 1034—1038 (1992); received August 9 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1034 
 Volume    47 
166Author    Wolfgang KurtzRequires cookie*
 Title    The Phase Transition of Potassium Sulfate  
 Abstract    The discontinuous phase transition of K 2 S0 4 is described by a semi-empirical model that uses the elastic stiffnesses c n and the changes in volume and entropy associated with the order-disorder transition. Consideration of the elastic anomaly (existence of soft, damped longitudinal acoustic phonons) in K 2 S0 4 removes the disagreement between transition enthalpies AH lr measured calori-metrically and AH tr derived from the p-T phase diagram via the Clausius-Clapeyron equation. The model used requires the knowledge of the c u (i = 1, 2, 3) which in many cases is not available in the literature. It is demonstrated that these values can be calculated with sufficient accuracy from the anisotropic displacement (Debye-Waller) factors which are routinely determined in crystal structure analyses and which, therefore, are available for many substances. There is fair agreement between the calculated strain energy and AH lr also for K 2 Se0 4 . In the case of K 2 Cr0 4 , use of published expansion data resulted in disagreement between calculated strain energy values and published, measured AH, r data. 
  Reference    Z. Naturforsch. 47a, 1039—1046 (1992); received July 4 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1039 
 Volume    47 
167Author    C. Herdlicka, J. Richter, M. D. ZeidlerRequires cookie*
 Title    Self-Diffusion in Molten Lithium Nitrate  
 Abstract    Self-diffusion coefficients of 7 Li + ions have been measured in molten LiN0 3 with several com-positions of 6 Li + and 7 Li + over a temperature range from 537 to 615 K. The NMR spin-echo method with pulsed field gradients was applied. It was found that the self-diffusion coefficient depends on the isotopic composition and shows a maximum at equimolar ratio. At temperatures above 600 K this behaviour disappears. 
  Reference    Z. Naturforsch. 47a, 1047—1050 (1992); received July 16 1992 
  Published    1992 
  Keywords    Molten salts, Self-diffusion, Isotope effect, NMR spin-echo 
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 Identifier    ZNA-1992-47a-1047 
 Volume    47 
168Author    Holger Hartwig, Helmut DreizlerRequires cookie*
 Title    A Contribution to the Microwave Spectra of eis-and trans-2,3-Dimethyloxirane 5y Fourier Transform Spectroscopy  
 Abstract    Microwave Fourier transform spectroscopy was used to reinvestigate the rotational spectra of cis-and trans-2,3-dimethyloxirane. The potential barriers hindering the internal rotation, internal rota-tion parameters, and partial restructures were determined. 
  Reference    Z. Naturforsch. 47a, 1051—1057 (1992); received June 24 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1051 
 Volume    47 
169Author    C. Gerke, H. DreizlerRequires cookie*
 Title    A Microwave Fourier Transform Spectrometer in the Frequency Range of 2 to 4 GHz and its Performance  
 Abstract    We present a microwave Fourier transform spectrometer with a coaxial cell in the range from 2 to 4 GHz. The performance is demonstrated by some examples showing the sensitivity and resolu-tion. 
  Reference    Z. Naturforsch. 47a, 1058—1062 (1992); received July 29 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1058 
 Volume    47 
170Author    Holger Hartwig, Helmut DreizlerRequires cookie*
 Title    The Rotational Spectrum of 2,2-Dimethyloxirane  
 Abstract    The microwave spectrum of 2,2-dimethyloxirane (isobutylene oxide) in the ground and torsionally excited states was assigned and analyzed. The potential barriers hindering the internal rotation described by V 3 = 11.312(9) kJ/mol and ^2 = 1.059(32) kJ/mol and the angles between the axes of inertia and the internal rotation axes were determined. 
  Reference    Z. Naturforsch. 47a, 1063—1066 (1992); received August 9 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1063 
 Volume    47 
171Author    Michael Krüger, Helmut DreizlerRequires cookie*
 Title    Methyl Internal Rotation and 14 N Nuclear Quadrupole Coupling from the Rotational Spectra of Ethyl Isocyanide, i5ö-Propyl Isocyanide and gauche-and trans-n-Propyl Isocyanide  
 Abstract    The barrier heights (F 3) hindering methyl internal rotation were determined with microwave Fourier transform spectroscopy from the ground vibrational state for the title molecules and found to be V 3 — 3.336(52) kcal/mol for ethyl isocyanide, V 3 > 3.1 kcal/mol for iso-propyl isocyanide, V 3 — 2.894(23) kcal/mol for gauche-n-propyl isocyanide and V 3 = 2.954(22) kcal/mol for trans-n-propyl isocyanide. The quadrupole coupling constants of iso-propyl isocyanide are x aa — 179.3(31) kHz, Xbb = —140(15) kHz and % ce — —39(15) kHz; the constants of trans-n-propyl isocyanide were determined to be x aa = 268.1 (71) kHz, x bb = ~ 108(23) kHz and x cc = ~ 160(23) kHz. 
  Reference    Z. Naturforsch. 47a, 1067—1072 (1992); received July 24 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1067 
 Volume    47 
172Author    MarcoL H Gruwel, RoderickE. WasylishenRequires cookie*
 Title    Molecular Motion in Phenpropylammonium Chloride Studied by Deuterium NMR  
 Abstract    Cation dynamics in phenpropylammonium chloride, C 6 H 5 (CH 2) 3 NH 3 Cr, were studied in three different solid phases by means of 2 H nmr. Both 2 H nmr line shapes and spin-lattice relaxation studies were performed on the ammonium head group, the adjacent methylene group and the phenyl-ring. In the low temperature phase, solid III, the -ND 3 group dynamics were dominated by C 3 jumps about the C-N axis. From the observed minima in T 1Z and T 1Q a quadrupole coupling constant of 165 ± 5 kHz was obtained. The 2 H nmr line shapes of the methylene group indicate that this group does not execute any large amplitude motion in the low temperature phase. In contrast, the phenyl ring deuterium nuclei give rise to line shapes characteristic of C 2 ring flips about the Cpara~C ipso aX * S " In the solid II phase the 2 H nmr line shapes of both the -ND ? and -CD 2 -groups are character-ized by asymmetric Pake powder patterns. Since one of the principal components of the electric field gradient tensor remains temperature independent for both groups, it was concluded that these groups perform planar large-amplitude motions between two sites. Axially symmetric spectra were obtained for all three groups in the high temperature phase, solid I. The 2 H nmr line shapes indicate the presence of whole ion reorientation about a molecular axis. In addition, the -ND 3 groups perform C 3 jumps about the C-N axis and the -C 6 D 5 group display line shapes characteristic for rotational diffusion about the C para -C ipso axis. 
  Reference    Z. Naturforsch. 47a, 1073—1086 (1992); received February 19 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1073 
 Volume    47 
173Author    Hiroyuki Ishida, Tatsuo Higashiyama, Naomi Hayama, Ryuichi IkedaRequires cookie*
 Title    *H NMR Studies on Cationic Motions in Solid tert-Butylammonium Hexachlorostannate (IV)  
 Abstract    The temperature dependences of the spin-lattice relaxation time (T t) and the second moment (M 2) of NMR absorptions were measured for anhydrous tert-butylammonium hexachloro-stannate(IV) and its partially deuterated analogs [(CD 3) 3 CNH 3 ] 2 SnCl 6 and [(CH 3) 3 CND 3 ] 2 SnCl 6 . Three kinds of cationic motions were revealed: the reorientations of the CH 3 group about their C-C bonds, the NH 3 group about its C-N bond, and the tert-butyl group about the C-N bond. Their motional parameters were determined. Among the three motions, the NH 3 motion occurs at the lowest temperature with quite a small activation energy (9.9-10.0 kJ mol -1). 
  Reference    Z. Naturforsch. 47a, 1087—1090 (1992); received July 8 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1087 
 Volume    47 
174Author    M. Liedtke, A. H. Saleck, J. Behrend, G. Winnewisser, R. Klünsch, J. HahnRequires cookie*
 Title    Rotational Spectrum of cis-HS 3 D  
 Abstract    The rotational spectrum of HS 3 D in the vibrational ground state has been measured in the frequency range between 75 and 293 GHz. Up to now, about 180 Q-, 30 P-, and 70 R-branch c-type transitions have been identified. The preliminary rotational constants of the species observed sup-port the cis-conformation established earlier from the H 2 S 3 rotational spectrum. 
  Reference    Z. Naturforsch. 47a, 1091—1093 (1992); received August 9 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1091 
 Volume    47 
175Author    A. Banerjee, T. HägerRequires cookie*
 Title    On some Crystals of "Lapis Lazuli"  
 Abstract    Some deep blue dodecahedral crystals from Afghanistan have been investigated by UV-, VIS-and IR-spectral pho-tometry and x-ray powder diffraction technique. Contrary to earlier identification, the crystals have been identified as hauynite. 
  Reference    Z. Naturforsch. 47a, 1094—1095 (1992); Received 
  Published    1992 
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 Identifier    ZNA-1992-47a-1094_n 
 Volume    47 
176Author    A. Pysik, J. HeberRequires cookie*
 Title    Experimental Realization of Stokes Modes of the Pipe by Lorentz Excitation  
 Abstract    The complete set of the Stokes modes of the pipe was first given by Brösa and Böberg. Two of these modes for an incompressible fluid were now realized in a transparent tube and detected by a laser light cut. Their velocity fields and lifetimes were compared with the theoretical predictions, and good agreement was found. The modes were generated by Lorentz force fields of appropriate symmetry induced by an electrical current through the fluid and external magnetic fields. For higher excitation intensities effects of mode coupling could be observed. 
  Reference    Z. Naturforsch. 47a, 1097—1104 (1992); received August 7 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1097 
 Volume    47 
177Author    D. J. Pusiol, R. Humpfer, F. NoackRequires cookie*
 Title    Nitrogen Nuclear Quadrupole Resonance Dips in the Proton Spin Relaxation Dispersion of Nematic and Smectic Thermotropic Liquid Crystals  
 Abstract    The Larmor frequency dependence of the proton spin relaxation time, obtained by means of the fast field-cycling NMR technique, has been used to study the 14 N quadrupole coupling constant K and its asymmetry parameter rj in the nematic and smectic phases of some liquid crystalline azoxybenzenes (PAA, BAB, HAB, HpAB), cyanobiphenyls (8CB, 9CB, 11CB) and oxycyano-biphenyls (9 OCB). Due to fast molecular reorientations, the effective quadrupole coupling constants are relatively small, whereas surprisingly the asymmetry parameters are rather large. The tempera-ture dependence of both K and rj within the mesophases, as well as their discontinuities at the different mesophase transitions, can be interpreted by the anisotropy of molecular rotations. It is found that temperature effects are significantly more pronounced for the (biaxial) smectic-C phase of the heptyloxyazoxybenzene (HpAB) than for the (uniaxial) smectic-A phase of the various inves-tigated cyano-and oxycyanobiphenyls. As a rule, tj turned out smaller in the smectic than in the nematic state, whereas K has similar values in both phases. 
  Reference    Z. Naturforsch. 47a, 1105—1114 (1992); received August 27 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1105 
 Volume    47 
178Author    S. Lewicki, B. Szafrańska, Z. PająkRequires cookie*
 Title    Molecular Motion in Solid Tetrapropylammonium Bromide and Iodide  
 Abstract    The proton NMR second moment and spin-lattice relaxation time for tetrapropylammonium bromide and iodide have been measured over a wide temperature range. A solid-solid phase transition related to the onset of cation tumbling was found for both salts and confirmed by DTA. In the low temperature phases methyl group reorientation was evidenced. For iodide a dynamic nonequivalence of the methyl groups and the onset of ethyl groups motion was also discovered. 
  Reference    Z. Naturforsch. 47a, 1115—1118 (1992); received July 14 1992 
  Published    1992 
  Keywords    NMR, Molecular motions, Phase transitions 
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 Identifier    ZNA-1992-47a-1115 
 Volume    47 
179Author    K. Indira, M. K. Rudra Warier, T. R. AnanthakrishnanRequires cookie*
 Title    Bending Energy Minimisation Criterion for Molecular Geometry in XY 3 Pyramidal Systems  
 Abstract    A study of the variation of the vibrational potential energy contribution with interbond angles in XY 3 pyramidal molecules confirms the observation previously made for XY 2 bend symmetric systems that the actual equilibrium configuration lies in the premises of minimum F bend and zero y stretch-bend * 
  Reference    Z. Naturforsch. 47a, 1119—1120 (1992); received July 11 1992 
  Published    1992 
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 Identifier    ZNA-1992-47a-1119 
 Volume    47 
180Author    Gerhard TaubmannRequires cookie*
 Title    A Modification of the Free-Electron Model for Cyclic Polyenes  
 Abstract    In the free-electron model (FE) of cyclic polyenes the 7r-electrons are allowed to move freely in a ring. A modification of the FE-model (the MFE-model) is discussed in which the N-fold symmetry due to the N C-atoms of the ring is taken into account by an appropriate potential. The results of the MFE-model are compared with HMO-theory. The sequence of degenerate and non-degenerate levels which determines the chemical properties (aromaticity and anti-aromaticity) of the annulenes is the same for both models. 
  Reference    Z. Naturforsch. 47a, 1121—1126 (1992); received July 27 1992 
  Published    1992 
  Keywords    HMO-theory, Free-electron model, Annulenes, Perturbation theory, Variation theory 
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 Identifier    ZNA-1992-47a-1121 
 Volume    47 
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