Go toArchive
Browse byFacets
Bookbag ( 0 )
Facet   section ZfN Section A:Volume 044  [X]
Facet   Publication Year 1989  [X]
Results  196 Items
Sorted by   
Publication Year
1989[X]
21Author    Pierre GuéretRequires cookie*
 Title      
 Abstract    A recently proposed set of symmetric maxwellian equations with a quantum-mechanical coupling term between matter and fields is investigated further. Monopole and dipole solutions are described, from which the momentum of a moving charge is calculated. An alternative derivation of the Dirac quantization condition for monopoles is given. F u r th e r P r o p e r tie s o f a S e t o f S y m m e tric M a x w e llia n E q u a tio n s 
  Reference    Z. Naturforsch. 44a, 106—108 (1989); received November 21 1988 
  Published    1989 
  Keywords    Dirac Electron, Magnetic Monopole, Maxwell's Equations 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0106.pdf 
 Identifier    ZNA-1989-44a-0106 
 Volume    44 
22Author    Z. NaturforschRequires cookie*
 Title      
 Abstract    The temperature dependence of the chlorine NQR frequency and spin-lattice relaxation rate indicate a structural phase transformation in (NH4)2PbCl6 at 80 K similar to that observed in (NH4)2TeCl6 at 85 K. Both transitions are characterized by a discontinuity of the temperature derivative of the NQR frequency shift and by a cusp in the NQR spin-lattice relaxation rate, but no splitting of the NQR line is observed below Tc. These observations point towards a transition that leaves the chlorine sites equivalent, such as a small angle rotation of the MXg"-octahedra about their threefold axis. Supplementary 'H-NMR measurements have been performed to investigate the direct influence of NH4 motion on the Cl-NQR. The phase transitions in mixed (NH4: K)2PbCl6 crystals have also been studied. PACS numbers: 76.60 Gv, 64.60-/ N Q R -N M R a n d R a m a n S tu d y o f a S tr u c tu r a l P h a s e T r a n s itio n in (N H 4) 2P b C l 6 
  Reference    Z. Naturforsch. 44a, 109—116 (1989); received November 28 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0109.pdf 
 Identifier    ZNA-1989-44a-0109 
 Volume    44 
23Author    MichaelC. Böhm, Gerd Bubeck, AndrzejM. OlesRequires cookie*
 Title     
 Abstract    M o d e l S tu d y o f I n s ta b ilitie s P r e s e n t in th e M e a n -F ie ld D e s c rip tio n a n d in L in e a riz e d C o r r e la tio n S c h e m e s In this work we discuss the cooperative occurrence of instabilities in the Hartree-Fock (HF) approximation and linearized correlation models. Both breakdown phenomena can be analyzed via eigenvalues of characteristic matrices. The well known HF instabilities follow from a quasi-degeneracy between the symmetry-adapted mean-field state and singly excited configurations. Quasi-degeneracies between the HF wave function and doubly excited configurations restrict the applicability of linearized correlation models. In the theoretical calculations the method of the local approach (LA) has been employed to derive the correlated ground state. For a system of the general topology XH2 (X = C, Si, etc.) the bond orbital approximation (BOA) has been used to derive analytic formulae indicating the stability range of linearized correlation schemes. Numerical calcula­ tions on the basis of a simple model-Hamiltonian are given for the n systems C2H4 and C2H2, respectively, which have been studied as a function of the CC bondlength. The comparison of the respective numerical data indicates that both breakdown phenomena are enhanced via coupling terms between strongly correlated bonds. 
  Reference    Z. Naturforsch. 44a, 117—124 (1989); received November 15 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0117.pdf 
 Identifier    ZNA-1989-44a-0117 
 Volume    44 
24Author    Atsushi Ishikawa, Tetsuo Asaji, Daiyu Nakamura, Ryuichi IkedaRequires cookie*
 Title     
 Abstract    S tu d y o f A n o n ic M o tio n s in S o lid R u b id iu m a n d C e siu m T e tr a c h lo r o a u r a te s (I I I) by M e a s u r in g th e T e m p e r a tu r e D e p e n d e n c e o f C h lo rin e N u c le a r Q u a d r u p o la r R e la x a tio n T im e s The temperature dependences of 35C1 NQR frequencies and 35C1 nuclear quadrupolar relaxation times r 1Q and T2Q were determined above 82K for Rb[AuCl4] and CsfAuClJ up to ca. 340 and 320 K, respectively. Below these temperatures two 35C1 NQR frequencies were observed for each complex whereas no resonance could be detected above the respective temperatures. For both complexes, TlQ observed below ca. 270 K was interpreted as mainly determined by the rotary lattice vibration around the pseudo-C4(C4) axis and each Cl-Au-Cl diagonal axis of the square planar complex anion, whereas Tiq observed above ca. 270 K was definitely shown to be determined through the reorientation of the anions about their C4 axis. The activation energies for the C4 reorientation of the anions was evaluated to be 71 and 53 kJ mol-1 for the rubidium and cesium salts, respectively. The anionic dynamics are discussed by assuming the motion of the anions within and out of the C4 potential wells at lower and higher temperatures, respectively. 
  Reference    Z. Naturforsch. 44a, 125—130 (1989); received December 10 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0125.pdf 
 Identifier    ZNA-1989-44a-0125 
 Volume    44 
25Author    F. Rohwer, R. Hinze, A. GuarnieriRequires cookie*
 Title      
 Abstract    The microwave spectrum of fluoroacetylene (HCCF) has been measured in the frequency region 35-260 GHz. Rotational constants of the ground state and rotational as well as rotation-vibrational interaction constants of several excited states of the C —C —H (v4) and the C —C —F (v5) bending vibrations have been obtained. E x te n d e d A n a ly s is o f th e R o ta tio n a l S p e c tr u m o f H C C F 
  Reference    Z. Naturforsch. 44a, 131—138 (1989); received December 16 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0131.pdf 
 Identifier    ZNA-1989-44a-0131 
 Volume    44 
26Author    Michacl Mahr, Helmut Paulus, KonradG. WeilRequires cookie*
 Title      
 Abstract    Nickel nitrate, nickel Perchlorate and cobalt nitrate can form homogeneous liquid phases with aniline and water. The shapes of the single phase regions in the ternary phase diagrams were determined. Five types of crystals were obtained in the system nickel nitrate/aniline/water. The structu­ res of Ni(N03)2 -6C6H7N • 2 H20 , Ni(N03)2-4C6H7N • 2 H20 , and Ni(N03)2-2C6H7N • 4 H20 have been determined by single crystal X-ray diffraction. All structures show chains of nickel ions and nitrate ions connected by water or aniline molecules. They can be interpreted as one dimensional ion pairs. C r y s ta llin e a n d L iq u id P h a s e s in th e S y s te m s M e X 2/A n ilin e /W a te r 
  Reference    Z. Naturforsch. 44a, 139—150 (1989); received November 11 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0139.pdf 
 Identifier    ZNA-1989-44a-0139 
 Volume    44 
27Author    Da Zhang, Michael Prager, Shi-Qi Dou, Alarich WeissRequires cookie*
 Title     
 Abstract    r y s ta l S tr u c tu r e o f B is (tr im e th y ltin) S e le n a te D ih y d r a te a n d R o ta tio n a l T u n n e llin g o f th e M e th y l G ro u p s Rotational tunnelling and librations of methyl groups in bis(trimethyltin) selenate dihydrate, [(CH3)3Sn]2Se04 • 2 H20, have been studied at low temperature using inelastic neutron scattering (INS) technique. Three tunnel transitions at 1.31 neV, 3.47 |ieV, and 21.0 (ieV of equal intensity were recorded. In the energy range of phonons a broad, slightly structured intensity distribution is observed. An attempt is made to identify and assign librational modes. The crystal structure of the title compound was determined by single crystal X-ray diffraction. [(CH3)3Sn]2Se04 • 2 H20 crystal­ lizes orthorhombic, space group D2*-Pbcn with 4 molecules in the unit cell. The lattice constants at room temperature are a = 1142.9(3) pm, b = 1304.6(4) pm, and c = 1084.6(3) pm. According to the molecular symmetry, the two "(CH3)3Sn(H20)" units in molecule are crystallographically equiva­ lent, but the three methyl groups bound to one Sn-atom are inequivalent. This result coincides well with the observation of three tunnel transitions in INS. A comparison with the related compound, bis(trimethyltin) sulfate dihydrate, is presented. The existence of hydrogen bonding and the role of intermolecular interactions on rotational tunnelling are discussed. 
  Reference    Z. Naturforsch. 44a, 151—159 (1989); received December 24 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0151.pdf 
 Identifier    ZNA-1989-44a-0151 
 Volume    44 
28Author    W.-H Steeb, JeunChyuan Huang, YihShun GouRequires cookie*
 Title     
 Abstract    C o m m e n t o n th e C h a o tic B e h a v io u r o f v a n d e r P o l E q u a tio n s w ith a n E x t e r n a l P e rio d ic E x c ita tio n The limit cycle system with an external periodic force d2u/df2 — a(1 — u2)du/dt + u" -/ccos(ßf) (n = 1, 3, 5,...) can show chaotic behaviour for certain values of a, k and Q. We study the influence of n on the chaotic behaviour. For n = 1 we select values which result in chaotic motion of the system. Then we investigate the behaviour of the system for n = 3, 5 and 7. Introducing the nonlinearity u"(n — 3, 5, 7) gives the surprising result that the chaotic motion ceases to exist. It is well known that the differential equation 
  Reference    Z. Naturforsch. 44a, 160—162 (1989); received November 8 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0160.pdf 
 Identifier    ZNA-1989-44a-0160 
 Volume    44 
29Author    R. Blinc, O. Jarh, A. Zidanšek, J. StefanRequires cookie*
 Title    NM R Determination of the Fractal Geometry of Gels Around the Collapse Transition  
 Abstract    The increase in the surface to volume ratio at the collapse transition of gels can be exploited to allow for an NMR determination of the fractal dimension of the gel surface in the liquid state where this quantity is hard to measure with other techniques. The measured quantities are the ratio be­ tween the spin-lattice and spin-spin relaxation times TJT2 of the liquid component and the ratio of the masses or volumes of the gel before and after the collapse transition. The tech­ nique has been used to determine the surface fractal dimen­ sion of a blood plasma gel. 
  Reference    Z. Naturforsch. 44a, 163—164 (1989); received September 22 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0163_n.pdf 
 Identifier    ZNA-1989-44a-0163_n 
 Volume    44 
30Author    Gerold Baier, Klaus WegmannRequires cookie*
 Title     
 Abstract    r a n s itio n to C h a o s via C o lla p s e o f T w o -T o r u s in th e B elousov-Z h a b o tin s k y R e a c tio n The transition of the dynamics of the Belousov-Zhabo-tinsky reaction from large peak oscillations to two-torus and chaos as a function of the flow rate is described. 
  Reference    Z. Naturforsch. 44a, 165—166 (1989); received November 8 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0165_n.pdf 
 Identifier    ZNA-1989-44a-0165_n 
 Volume    44 
31Author    Hans SallhoferRequires cookie*
 Title    Hydrogen in Electrodynamics II. M athem atical Means  
 Abstract    , 1989 (2/+1) m P,m — sin 9 cos 9 dcos0 P,' sin 9 = (/+ l)(/ + m)(/ + m -l) P ^ 1 + /(/-wi + l)(/-u i + 2) Pt™71 (2/+1) sin 29dcos0P r 
  Reference    Z. Naturforsch. 44a, 167—168 (1989); received January 20 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0167_n.pdf 
 Identifier    ZNA-1989-44a-0167_n 
 Volume    44 
32Author    G. KlicheRequires cookie*
 Title    L a ttic e  
 Abstract    V ib r a tio n s o f th e C o o p e rite s P d O a n d P t S The vibrational spectra of the cooperite type compounds PdO and PtS (space group P42/mmc — D4h, Z = 2) are analyzed. Good agreement between experimental and calculated lattice vibration frequencies is obtained using a force field which includes short-range force constants only. This demonstrates a highly covalent bonding character of the cooperites. 
  Reference    Z. Naturforsch. 44a, 169—172 (1989); received December 3 1988 
  Published    1989 
  Keywords    Vibrational spectra, normal coordinate analysis, force constants, cooperite-type com­ pounds 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0169.pdf 
 Identifier    ZNA-1989-44a-0169 
 Volume    44 
33Author    W. Waschkowski, K. Knopf, L. KoesterRequires cookie*
 Title      
 Abstract    Scattering of Slow Neutrons by Thorium We determined by means of Christiansen filter technique and transmission measurements the following quantities for thorium: -the coherent scattering length b =10.31 ± 0.03 fm, -the absorption cross section at 0.0253 eV er., = 7.34 ± 0.09 b, -the potential scattering radius R = 9.6 ± 0.2 fm. In combination with scattering cross sections in the eV-energy region we obtained information about bound levels at negative energies. 
  Reference    Z. Naturforsch. 44a, 173—179 (1989); eingegangen am 31. Januar 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0173.pdf 
 Identifier    ZNA-1989-44a-0173 
 Volume    44 
34Author    F. Burgäzy, H. Jaeger, K. P. Schulze, S. Lamparter, SteebRequires cookie*
 Title    X -R a  
 Abstract    y E m issio n a n d X -R a y S e lf-A b s o rp tio n in th e H ig h -Tc S u p e r c o n d u c to r Y B a 2C u 30 6 9 a n d o th e r C o p p e r O x id e s O-K, X-ray emission spectra of La2Cu04 and YBa2Cu30 6 9 are compared with calculated spectra. It is shown from O-K^ emission spectra of YBa2Cu3Ov with varying oxygen content (6.0 < -X < 6.9) that with heating the superconducting compound (x = 6.9) oxygen atoms are re­ moved from the Cu-O chains. A method for comparing X-ray self-absorption spectra from com­ pounds with different concentrations of the element under consideration is presented. Cu-L self-absorption spectra of YBa2Cu3Ox (6.0 < x < 6.9) are compared with those of Cu, Cu20, CuO, and NaCuOn. By this comparison and from O-K., emission spectra, oxygen 2p holes are found to be present in the superconducting compound. The ionic character of the Cu-O bonds in the non-superconducting green phase Y2BaCuO? is shown with 0 -K 3 emission and Cu-L3 self-absorption spectroscopy. The energy gap of Y,BaCu05 is found to be about 5eV. 
  Reference    Z. Naturforsch. 44a, 180—188 (1989); received December 22 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0180.pdf 
 Identifier    ZNA-1989-44a-0180 
 Volume    44 
35Author    P. Kizler, P. Lamparter, S. SteebRequires cookie*
 Title    X -R a  
 Abstract    y A b s o r p tio n N e a r E d g e S tr u c tu r e (X A N E S) C a lc u la tio n s f o r th e A m o rp h o u s F e 80B 20-a n d N i 80B 20-A llo y s Xanes spectra of the amorphous Fe80B20-and Ni80B20-alloys have been investigated using the electron multiple scattering theory of Durham et al. The calculations were based on several models for the structure of amorphous Fe80B20 and Ni80B20. Very good agreement between theoretical and experimental XANES curves was met. Opposite to former expectations for obtaining information on bond angles by XANES, this study shows that XANES points to more complex features of the structure than can be expressed in terms of bond angles. 
  Reference    Z. Naturforsch. 44a, 189—194 (1989); received December 22 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0189.pdf 
 Identifier    ZNA-1989-44a-0189 
 Volume    44 
36Author    M. Koch, F. Temps, R. Wagener, H. Gg, WagnerRequires cookie*
 Title      
 Abstract    Absolute values for the removal rates of CH2(ä »AJ by NH3, CH3NH2, CH3OH, HCl, and HF have been determined in the gas phase at low pressures and room temperature. CH2(ä 'AJ was generated by pulsed laser photolysis of CH2CO. The measurements were carried out by observing the laser induced fluorescence of 'CH2 after excitation by a pulsed laser as a function of the time delay between the photolysis and analysis pulses. The overall rate constants were found to be 2.4, 2.4, 2.3, 1.6 and 0.13 • 1014 cm3/mol s, respectively. NH2 was shown by LIF detection to be a primary product of the reaction of :CH2 with NH3. The intersystem crossing channel of 'CH2 was investigated by monitoring the formation of CH2(X3B,) with laser magnetic resonance. LMR absorption intensities of 3CH2 resulting from quenching of 'CH2 in the presence and absence of the reactant R were compared under otherwise identical conditions. The branching ratios of quenching versus total removal of 'CH, turned out to be 0.30, 0.13 and 0.98 for NH3, CH3OH, and HF, respectively. 
  Reference    Z. Naturforsch. 44a, 195—204 (1989); received November 19 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0195.pdf 
 Identifier    ZNA-1989-44a-0195 
 Volume    44 
37Author    M. Zander, G. KirschRequires cookie*
 Title     
 Abstract    n th e P h o s p h o re s c e n c e o f B e n z o lo g u e s o f F u r a n , T h io p h e n e , S e le n o p h e n e , a n d T e llu ro p h e n e . A S ystem atic S tudy o f the In tra -a n n u la r In te rn al H eavy-atom Effect In memory of the late Professor Oskar E. Polansky Phosphorescence in ethanol and n-pentane at 77 K of the benzologues 1-8 of furan, thiophene, selenophene and tellurophene has been investigated. The rate constants of both the radiative (A .PT) and non-radiative (A :GT) deactivation of the lowest triplet state correlate linearly with X cl C2 where ck denotes the Hückel AO coefficients in the HOMO of the carbon atoms bound to the hetero-atom and (is the spin-orbit coupling constant of the hetero-atom present. -The linear correlation observed between A .PT and kGT is an example for the Orlandi-Siebrand rule. -The influence of an external heavy-atom perturber (methyl iodide) on phosphorescence lifetimes and the vibrational structure of phosphorescence spectra is the more efficient the less efficient is the internal perturbation caused by the intra-annular heavy-atom. 
  Reference    Z. Naturforsch. 44a, 205—209 (1989); received January 24 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0205.pdf 
 Identifier    ZNA-1989-44a-0205 
 Volume    44 
38Author    Motohiro Mizuno, Tetsuo Asaji, Daiyu NakamuraRequires cookie*
 Title     
 Abstract    f th e M ix e d C r y s ta l o f (N H 4) 2(1_ x)K 2xP b | C u (N 0 2) 6] a n d th e R e o r ie n ta tio n o f A m m o n iu m Io n s in th e C r y s ta ls With decreasing temperature, the mixed crystal (NH4)2(1 _x)K2;cPb[Cu(N02)^] at low potassium concentrations yields four solid phases, I, II, III, and IV. With increasing potassium concentration, the phase transition between III and IV disappears. By DTA, the corresponding transition tempera­ ture Tc was measured as a function of .x. The mechanism of the phase transition is discussed, considering the reorientational motion of ammonium ions. The activation energy of (3 ± 1) kJ mol ~1 for the motion of the ammonium ions obtained from our model agrees well with the experi­ mental value of (2 + 0.5) kJ mol ~1 for the same motion in diamagnetic (NH4)2Cd2(NÖ2)6, which was studied as reference compound because its crystal structure is very similar. Tc of (NH4)2Pb[Cu(N02)6] increased from 94 to 99 K by deuteration. This isotope effect is well inter­ preted in terms of the above model. T h e L o w e s t-T e m p e ra tu re P h a s e T r a n s itio n 
  Reference    Z. Naturforsch. 44a, 210—214 (1989); received January 7 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0210.pdf 
 Identifier    ZNA-1989-44a-0210 
 Volume    44 
39Author    Ch Keussen, N. Heineking, H. DreizlerRequires cookie*
 Title     
 Abstract    M ic ro w a v e F o u r ie r T ra n s fo rm S p e c tr o m e te r in th e F re q u e n c y B a n d F r o m 26 to 4 0 G H z We report the design and performance of a microwave Fourier transform spectrometer in the frequency region between 26 and 40 GHz for the investigation of rotational spectra. The performan­ ce is illustrated by rotational transitions of allene and allene-d4 molecules with a very small dipole moment in vibrational excited states. The sensivity and Doppler limited linewidth is demonstrated by measurements of transitions of isotopomers of carbonyl sulfide and sulfur dioxide. 
  Reference    Z. Naturforsch. 44a, 215—221 (1989); received January 12 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0215.pdf 
 Identifier    ZNA-1989-44a-0215 
 Volume    44 
40Author    M. Mattes, SorgRequires cookie*
 Title     
 Abstract    A Riemann-Cartan structure can be associated to any SO (4) trivializable gauge field. Under certain integrability conditions, this non-Riemannian geometry may be replaced by a strictly Riemannian one. The Yang-Mills equations guarantee the existence of such a Riemannian structure. The general SO(4) trivializable solution for the SO(3) Yang-Mills equations is discussed within the geometric approach. R ie m a n n -C a r ta n G e o m e try o f T riv ia liz a b le G a u g e F ie ld s 
  Reference    Z. Naturforsch. 44a, 222—238 (1989); received September 1 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0222.pdf 
 Identifier    ZNA-1989-44a-0222 
 Volume    44 
Prev
1
2
3
4
5
...
Next