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2000 (1)
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1Author    M. F. MahmoodRequires cookie*
 Title    Polarized Chirped Soliton Oscillations in a Lossy Elliptically Low Birefringent Optical Fiber  
 Abstract    Using a variational method, a new model of the nonlinear propagation of optical solitons generated from semiconductor lasers through a lossy elliptically low birefringent fiber, is presented within the frame-work of a system of coupled nonlinear Schroedinger (CNLS) equations. This model demonstrates polar-ized soliton oscillations in a lossy elliptically low birefringent fiber. 
  Reference    Z. Naturforsch. 55a, 941—944 (2000); received September 16 2000 
  Published    2000 
  Keywords    Solitons, Birefringence, Polarization, Optical Fiber 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0941.pdf 
 Identifier    ZNA-2000-55a-0941 
 Volume    55 
2Author    Michael SpringborgRequires cookie*
 Title    A Comparison between Polyatecylene and Polycarbonitrile  
 Abstract    Results of a theoretical, comparative study of the electronic properties of trans-polyacetylene and polycarbonitrile are reported. Polyacetylene consists of zigzag chains of CH units, whereas poly-carbonitrile has every second CH unit replaced by an N atom. Ground-state properties (structure, electronic bonds and bands, densities of states, momentum distributions, and reciprocal form factors) of the periodic, infinite, isolated chains are studied by means of first-principles, density-functional calculations. It is demonstrated how the presence of the (nitrogen) heteroatoms in the backbone of polycarbonitrile leads to a partial localization of the electrons. In order to investigate charged chains, model calculations are subsequently performed. These indicate solitons but not polarons to be stable. In total, the analysis demonstrates how the combination of information that can be obtained from various experiments provides a detailed description of the compounds. 
  Reference    Z. Naturforsch. 48a, 159—164 (1993); received November 26 1991 
  Published    1993 
  Keywords    Conjugated polymers, Structure, Electronic structure, Momentum densities, Solitons 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0159.pdf 
 Identifier    ZNA-1993-48a-0159 
 Volume    48 
3Author    Ch Frommen, M. Mangold, J. PeblerRequires cookie*
 Title    Magnetic Solitons in the 1-D Antiferromagnetic Chains of Li 2 Mn 0 98 Fe 0 02 F 5 and Na 2 Mn 0 98 Fe 0 0 2 F 5  
 Abstract    Measurements of the 57 Fe Mössbauer effect and magnetic susceptibility have been performed on 57 Fe-doped quasi-l-d antiferromagnetic chains of Li 2 MnF 5 and Na 2 MnFg as a function of temper-ature. The Mössbauer spectra, fitted by the Blume-Tjon model, show definite relaxation effects near the Neel temperature, which are attributed to short-range order with temperature-dependent relax-ation times. The soliton model of non-linear excitations was applied. Experimental data confirm the predicted exponential temperature dependence of the thermal excitation of moving domain walls. From the activation energies E 2 Jk 2 as a function of 1-d exchange energies J/k the local anisotropy energy D/k of —3.7(2) K was derived on the basis of sine-Gordon theory. This result is in fair agreement with —3.5(1) K previously derived from magnetic susceptibility measurements. In the light of our results there is some evidence that at low bridging angle ß % 102(5)° a phase-transition from antiferromagnetic to ferromagnetic ordering occurs. 
  Reference    Z. Naturforsch. 51a, 939—949 (1996); received February 1 1996 
  Published    1996 
  Keywords    Magnetization Exchange and Anisotropy Energy, Relaxation, Solitons 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0939.pdf 
 Identifier    ZNA-1996-51a-0939 
 Volume    51