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161	Author	Felipe Lorenzo, JoseL. Alonso, J.-U Grabow, H. Dreizler	Requires cookie*
	Title
	Abstract	As a first example in a series of substituted thiiranes we present an investigation of the nuclear quadrupole coupling in 33 S-methylthiirane in natural abundance. The rotational and quadrupole coupling constants are: A = 11 599.0976(18) MHz, £ = 4815.6822(6)MHz, C = 3909.1318 (5) MHz, X aa = -12.7731 (82) MHz, x bb = -20.3366(118) MHz, x cc = 33.1097(273) MHz.
	Reference	Z. Naturforsch. 51a, 1096—1098 (1996); received August 7 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1096
	Volume	51

162	Author	Holger Hartwig, Helmut Dreizler	Requires cookie*
	Title	Analysis of Internal Rotation and Determination of the Heavy Atom Structure of anti-2,3-Dimethylthiirane by Fourier Transform Microwave Spectroscopy
	Abstract	We used the advanced technique of Fourier transform microwave spectroscopy to measure and assign the ground state rotational spectrum of anti-2,3-dimethylthiirane, and to analyse the internal rotation of the two methyl groups. The potential parameters obtained are V3 = 13.1678(21) and V] 2 = —1.6678(25) kJ/mol. The measurement and assignment of the 13 C and ?4 S isotopomers in the ground state allowed to determine the molecular structure of the heavy atom frame using the r s and ro methods.
	Reference	Z. Naturforsch. 51a, 1099—1106 (1996); received September 10 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1099
	Volume	51

163	Author	Jens-Uwe Grabow, Helmut Dreizler	Requires cookie*
	Title	of awri-2,3-Dimethylthiirane
	Abstract	The rotational spectrum of 33 S a/j//'-2,3-dimethylthiirane with its 33 S nuclear quadrupole coupling hyperfine structure in the range 7.6 to to 21.5 GHz and its analysis is reported. The rotational con-stants are A = 5331.1401(5), B = 3506.3963(10), and C = 2356.9273(2) MHz. The 33 S quadrupole coupling constants are \aa = 8.3871(93), Xbb = -32.3291(174), and Xcc = 23.9420(174) MHz.
	Reference	Z. Naturforsch. 51a, 1107—1109 (1996); received September 10 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1107
	Volume	51

164	Author	Jens-Uwe Grabow, Masao Onda, Helmut Dreizler	Requires cookie*
	Title	of 2,2-Dimethylthiirane
	Abstract	The rotational spectrum of 33 S 2,2-dimethylthiirane with its 33 S nuclear quadrupole coupling hyperfine structure in the range 8.9 to 20.0 GHz and its analysis is reported. The rotational constants are A = 5507.4663(3), B = 3440.58395(18), and C = 2978.5723(3) MHz. The 33 S quadrupole coupling constants are X aa = -22.6390(23), \bb = 47.1830(50), and Xcc = -24.5440(50) MHz.
	Reference	Z. Naturforsch. 51a, 1110—1112 (1996); received September 10 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1110
	Volume	51

165	Author	He, H., M. Pernpointner, H. Preuß	Requires cookie*
	Title	Die Lösung der Schrödinger-Gleichung als eindimensionales Problem. IV. Erfassung von Korrelation am Beispiel der Zweielektronensysteme Solving the Schrödinger-equation as a One-dimensional Problem. IV. Correlation contributions for the two-electron systems He and HT applying the one-dimensional formalism
	Abstract	After calculating ground and excited states of one-electron systems with improved discretization methods in Part III of this work it is shown that also correlation contributions can be yielded by this formalism. The more powerful discretization methods are applied to the two-electron systems He and H^. For multi-electron systems the symmetry properties of the wave function become important but in the case of two-electron systems an antisymmetric spin part can be separated and the integral kernel containing the spatial part of the wavefunction has therefore to be symmetric.
	Reference	Z. Naturforsch. 51a, 1113—1122 (1996); eingegangen am 6. September 1996
	Published	1996
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	TEI-XML for	default:Reihe_A/51/ZNA-1996-51a-1113.pdf
	Identifier	ZNA-1996-51a-1113
	Volume	51

166	Author	J. Kastner, B. D. Mosel, W. Müller-Warmuth	Requires cookie*
	Title	EPR Studies of Cr 3+ and Fe 3+ in Host Crystals with Langbeinite Structure
	Abstract	Electron paramagnetic resonance (EPR) spectra of trivalent chromium and iron ions have been investigated in host crystals of double sulfates with langbeinite structure, A 2 B 2 (S0 4) 3 , with A = NH 4 , Rb + , Tl + and B = Cd 2 + , Mg 2 + . In most cases, single crystals could be grown, and the spin Hamiltonian parameters have been determined from the rotational diagrams. Powder spectra were analyzed and simulated as well. Three centres of axial symmetry with different zero field splittings have been observed for Cr 3 + , and two for Fe 3 + . The trivalent impurity ions have been shown to occupy divalent lattice sites substitutional^, but the environments are different depending on the structure and the mechanism of charge compensation. A qualitative description of the incorporation of dopants has been possible on this basis, taking into account the local relaxation and the ligand field stabilization effects. Temperature dependent single crystal and powder measure-ments have provided information on the zero field splitting and phase transitions.
	Reference	Z. Naturforsch. 51a, 1123—1133 (1996); received August 28 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1123
	Volume	51

167	Author	Liang-Hsuan Kuo, Zdenek Slanina, Teh-Chang Chou	Requires cookie*
	Title	Additions of Cyclopentadiene to a Dissymmetric Maleic Anhydride: Semiempirical Calculations of Their Thermodynamics and Kinetics
	Abstract	There are four conceivable products of the title addition, however only two of them have been prepared. MNDO, AMI, and PM3 quantum-chemical computations have been used in order to rationalize the observation. Activated complexes have been computed for the four possible addi-tions and it was found that one C-C bond rather than two is created on the path from the reactants to the activated complex (the C-C bond varies between 1.70 and 1.87 A). Only one activated complex has been localized on each reaction path. The two types of products observed in experiment are computed to be both thermodynamically more stable and kinetically more feasible, and hence the computations agree with the observations.
	Reference	Z. Naturforsch. 51a, 1134—1138 (1996); received July 23 1996
	Published	1996
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	TEI-XML for	default:Reihe_A/51/ZNA-1996-51a-1134.pdf
	Identifier	ZNA-1996-51a-1134
	Volume	51

168	Author	S. Hartwig	Requires cookie*
	Title	Langjährige Be 7 -Bodenluftmessungen lassen Änderung des atmosphärischen Austauschverhaltens während der letzten Jahrzehnte vermuten Ground Level Be 1 -Concentration Measurements for Many Years Indicate a Change of Atmospheric Exchange Processies During the Last Decades
	Reference	Z. Naturforsch. 51a, 1139—1143 (1996)
	Published	1996
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	TEI-XML for	default:Reihe_A/51/ZNA-1996-51a-1139.pdf
	Identifier	ZNA-1996-51a-1139
	Volume	51

169	Author	L. Schmidt, A. M. Popova, V. V. Komarov, H. Jungclas	Requires cookie*
	Title	Dissociation of Slow Polyatomic Molecules by Grazing Scattering at Surfaces
	Abstract	We consider polyatomic molecules containing peripheral chains of valence groups, which slide along crystallic surfaces at grazing incidence. The periodically located Coulomb centres of the crystallic surfaces interact with the moving valence group dipoles like a time-dependent oscillation potential. This interaction can lead to multiple resonant vibrational excitations of the peripheral valence group dipoles. Accumulation of such collective excitations in the valence group chains (excimols) eventually can lead to the cleavage of particular bonds (trap bonds) inside the molecule. A model for this complex process is presented including a parameterised formula for the dissociation probability of polyatomic molecules scattered by a surface at grazing incidence. The model is supported by the experimental observation of dissociation energy thresholds.
	Reference	Z. Naturforsch. 51a, 1144—1152 (1996); received June 26 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1144
	Volume	51

170	Author	A. Kawski, A. Kubicki, J. Kamiński, B. Kukliński, T. Nowosielski	Requires cookie*
	Title	Photoluminescence Properties of trans-4,4'-Diamino-stilbene in Polyvinyl alcohol) Films
	Abstract	Experimental studies have shown that the nonpolar molecule 4,4'-diamino-stilbene (DAS) in polyvinyl alcohol) film (PVA) at 296 K, apart from fluorescence displays phosphorescence whose intensity differs only slightly from that observed at 84 K. The overlapping of fluorescence and phosphorescence bands is the reason of the unusual behaviour of the emission anisotropy in the longwave absorption and photoluminescence bands. A distinct effect of direct irradiation on the intensity of these bands was observed.
	Reference	Z. Naturforsch. 51a, 1153—1156 (1996); received October 8 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1153
	Volume	51

171	Author	Roy Tärneberg	Requires cookie*
	Title	Sulphate Rotator Phases in Polarised Light
	Abstract	Li 2 S0 4 has a well defined high-conducting fee phase in the temperature range 577-860 °C, and LiNaS0 4 a bcc phase in the range of 518-614 °C. Both salts were studied in polarised light during sequences going from melt, through the cubic phase into the "room temperature" phase, and back to the cubic phase. The two cubic sulphate phases are compared with organic plastic rotator phases, especially regarding the formation of vapour snakes.
	Reference	Z. Naturforsch. 51a, 1157—1160 (1996); received June 29 1996
	Published	1996
	Keywords	Plastic phases, rotator phases, vapour snake, lithium sulphate, lithium sodium sulphate
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	Identifier	ZNA-1996-51a-1157_n
	Volume	51

172	Author	Feng Qing-Zeng	Requires cookie*
	Title	Pattern Formation in Force-free Magnetic Fields and Beltrami Flows
	Abstract	Force-free magnetic fields and Beltrami flows, which are selenoidal vector fields and satisfy the condition that the field vector is everywhere parallel to its curl, have complex topological structures and usually show chaotic behavior. The lines of force are determined by the equations of a 3-D (dimensional) dynamical system. In the integrable case, all lines of force lie on some families of tori. If the integrable solution undergoes a small perturbation, most of the original tori still exist but undergo a slight distortion (KAM tori). Near the original heteroclinic cycles emerges a chaotic layer. By superposition of the basic solutions of force-free magnetic fields one can get very complicated pictures: a single line of force could be space filling within some subspace of a 3-D region, which has a fractional dimension and a positive Lyapunov exponent, i.e. one gets a chaotic line of force or a fractal. At the same time there are still ordered regions in the chaotic surroundings. Tubes of force which are tangled or self-knotted embed in the chaotic sea. The KAM tori can also be disrupted through resonances, leading to increased chaotic regions. Thus, the effect of nonlinear dynamics plays an important role in the pattern formation of force-free magnetic fields and Beltrami flows.
	Reference	Z. Naturforsch. 51a, 1161—1169 (1996); received September 5 1996
	Published	1996
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	TEI-XML for	default:Reihe_A/51/ZNA-1996-51a-1161.pdf
	Identifier	ZNA-1996-51a-1161
	Volume	51

173	Author	Takashi Tsuchiya	Requires cookie*
	Title	The Critical Amplitude for Bifurcation Points of the Logistic Map
	Abstract	The phenomenon called critical slowing down is studied for some analytically tractable bifurca-tion points of the logistic map. The critical amplitude and the critical amplitude ratio are introduced to describe the critical behaviors more precisely when the critical exponents are identically unity for two critical behaviors which are to be compared. Since Hao predicted unity of the critical exponent for 1-d maps assuming exponential damping of the distance from the attractor, the assumption is checked. The result is that the shrinkage of the valid region of the assumption occurs as the adjustable parameter approaches one of the bifurcation points.
	Reference	Z. Naturforsch. 51a, 1170—1174 (1996); received September 25 1996
	Published	1996
	Keywords	Bifurcation, Logistic map, Critical slowing down, Critical exponent, Critical amplitude
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	TEI-XML for	default:Reihe_A/51/ZNA-1996-51a-1170.pdf
	Identifier	ZNA-1996-51a-1170
	Volume	51

174	Author	I. C. Moreira	Requires cookie*
	Title	The "Triptych" Function -Determining the Basins of Attraction of One-Dimensional Maps
	Abstract	We show that a modification of the path length method, introduced by R. Richter et al. [Z. Naturforsch. 49 a, 871 (1994)], gives us a method for finding basins of attraction of one-dimensional maps with multiple attractors.
	Reference	Z. Naturforsch. 51a, 1175—1178 (1996); received July 6 1996
	Published	1996
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	TEI-XML for	default:Reihe_A/51/ZNA-1996-51a-1175.pdf
	Identifier	ZNA-1996-51a-1175
	Volume	51

175	Author	H. Uhlig, M. Fließ, J. Dürr, R. Bellissent, H.-P Lamparter, F. Aldinger, S. Steeb	Requires cookie*
	Title	A Diffraction Study of Amorphous Si 040 C 024 N 036
	Abstract	In the present work, amorphous Sio.40Co.24No.36 samples were investigated. X-ray and neutron diffraction experiments were performed, in order to evaluate the structure factors by the method of contrast variation. The structure can be described as crosslinked Si-N-C matrices. Within these matrices SiN 4 tetrahedra are predominant. Direct Si-Si contact does not occur. We report on the short range order and the nature of chemical bonding.
	Reference	Z. Naturforsch. 51a, 1179—1184 (1996); received September 19 1996
	Published	1996
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	TEI-XML for	default:Reihe_A/51/ZNA-1996-51a-1179.pdf
	Identifier	ZNA-1996-51a-1179
	Volume	51

176	Author	IvoK. Grabtschev, IvankaT. Moneva, Eryk Wolarz, Danuta Bauman	Requires cookie*
	Title	New Unsaturated 1,8-Naphthalimide Dyes for Use in Nematic Liquid Crystals
	Abstract	The properties of new fluorescent dyes (derivatives of unsaturated 1,8-naphthalimide) are stud-ied. Spectral characteristics of the dyes are recorded in both isotropic (ethanol, dioxane) and anisotropic (nematogenic liquid crystal mixture ZLI 1840) media. The optical, electro-optical, and thermodynamical properties of the liquid crystal-dye mixtures are examined. The orientational order parameters are evaluated to be within 0.4 -0.5, depending upon the dye's molecular structure. Additionally, the influence of chemical bounding of the dyes to polystyrene chains on the phase transition temperature from the nematic to the isotropic state of polymer / liquid crystal mixtures is investigated. The low-molecular-mass dyes do not markedly affect the clearing point of pure liquid crystal, while the dye-styrene copolymers lower the transition temperature and widen the two-phase region at the transition. The electro-optical properties of the dye / liquid crystal systems imply potential utilization of the dyes studied in the so called "guest-host" liquid crystal displays.
	Reference	Z. Naturforsch. 51a, 1185—1191 (1996); received June 25 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1185
	Volume	51

177	Author	Danuta Bauman, Eryk Wolarz	Requires cookie*
	Title	Study of Orientational Order of Liquid Crystal 8 OCB Doped with Perylene-like Dyes by Means of Polarized Optical Spectroscopy
	Abstract	Measurements of the polarized absorption and fluorescence spectra for perylene-like dyes dis-solved in a liquid crystal 8 OCB have been used to study the long-range orientational order in the smectic A and nematic phases. The temperature dependence of the order parameters <P,> and has been investigated and the orientational distribution function has been determined. On the basis of the experimental order parameter values some information about the orientation of molecules in guest-host mixtures has been obtained.
	Reference	Z. Naturforsch. 51a, 1192—1196 (1996); received October 5 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1192
	Volume	51

178	Author	Hiromitsu Terao, Tsutomu Okuda, Sachiyo Uyama, Hisao Negita, Shi-Qi Dou, Hartmut Fuess, Alarich Weiss	Requires cookie*
	Title	Crystal Structure Refinement and Single Crystal 81 Br Zeeman NQR Study of KHgBr 3 H 2 0
	Abstract	Three 81 Br NQR resonance lines of KHgBr 3 H 2 0 were detected between 77 K and room temperature. From the Zeeman effect measurement on a single crystal the nuclear quadrupole coupling constants (e 2 qQ/h) and the asymmetry parameters (r/) were obtained, which are 228.42 MHz and 0.005, 226.24 MHz and 0.005, and 108.76 MHz and 0.465 for e'qQIh and rj at 295 K, respectively. Large deviations of the observed directions of electric field gradient tensors from the directions expected from previous X-ray results have been found. With the present X-ray redetermination, 1 Br NQR and structure are in good agreement. The structure and bonding in the compound are discussed.
	Reference	Z. Naturforsch. 51a, 1197—1202 (1996); received June 14 1996
	Published	1996
	Keywords	KHgBr v H 2 0, X-Ray analysis, NQR, Crystal structure, Chemical bonding
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	Identifier	ZNA-1996-51a-1197
	Volume	51

179	Author	S. Heinemann, H. Kresse, S. Urban, R. Dabrowski	Requires cookie*
	Title	Dielectric Investigations in Smectic B-Phases
	Abstract	Several liquid crystalline substances exhibiting S B -phases have been investigated by dielectric and calorimetric measurements. Special attention is taken to the low frequency relaxation process at the phase transition nematic-S B . From the large change of relaxation frequencies, crystallinity of the S B -phases has been concluded. Nevertheless, motion is still present and not frozen.
	Reference	Z. Naturforsch. 51a, 1203—1208 (1996); received July 26 1996
	Published	1996
	Keywords	Smectic B-phase, Dielectric constant, Relaxation frequency, Transition entropy
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	Identifier	ZNA-1996-51a-1203
	Volume	51

180	Author	M. Bionducci, G. Licheri, A. Musinu, G. Navarra, G. Piccaluga, G. Pinna	Requires cookie*
	Title	The Structure of a Zn(II) Metaphosphate Glass. I. The Cation Coordination by a Combination of X-Ray and Neutron Diffraction, EXAFS and X-Ray Anomalous Scattering
	Abstract	In order to clarify the reason of some discrepancies existing in literature, the zinc coordination in a Zn metaphosphate glass has been investigated by the complementary use of X-Ray Diffraction, Neutron Diffraction, Extended X-ray Absorption Fine Structure Spectroscopy and X-Ray Anoma-lous Scattering. All the techniques indicate a tetrahedral coordination of O atoms around Zn :+ ions, the Zn-O distance being 1.94 ± 0.01 A. The simultaneous modelling of all the experimental data by Reverse Monte Carlo technique demonstrated that this coordination is consistent with an extended model in which metal ions are interposed between phosphate chains. The importance of describing the preparation conditions of the glasses is stressed when structural results have to be compared.
	Reference	Z. Naturforsch. 51a, 1209—1215 (1996); received September 17 1996
	Published	1996
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	Identifier	ZNA-1996-51a-1209
	Volume	51

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