2. Spezielle produkte und Anwendungsgebiete

Ohne Zusammenfassung     

Strukturelle und magnetische Untersuchungen an Hexachlorowolframaten(V)

Structural and Magnetic Investigations of Hexachlorotungstates(V) CsWCl₆ crystallizes in the monoclinic space group C2/c with the lattice dimensions a = 12.097(8), b = 6.327(5), c = 15.30(1) Å, β = 128.4(1)° and 4 formula units. The compounds AWCl₆ (A = Rb, K, NH₄) are isotypic with CsWCl₆ as shown by powder patterns. Single-crystal photographs of [N(C₂H₅)₄]WCl₆ show monoclinic symmetry, space group P2₁/n with a = 11.737(8), b = 10.239(7), c = 7.191(5), β = 101.46(8)° and Z = 2. Both structures are composed of scarcely deformed WCl₆ octahedra. The trigonal compression of the octahedra results in a slightly negative deformation parameter according to the Figgis-model of the magnetic behaviour of d¹-systems. Above 80 K the μ² vs. T-curve is linear. This leads to a spin-orbit coupling constant of 1250 ± 200 cm^?1 and a covalence parameter of 0.6–0.8. Comparing the spectra of WCl₆, CsWCl₆ and Cs₂WCl₆ the beginning of the charge-transfer region was determined. The crystal field strength for CsWCl₆ was found as Δ = 16 000 cm^?1.     

On the occurrence of naked singularities in general relativity

It is shown that spherically symmetric collapse can lead to singularities which arenot hidden within black holes.Work supported by the Deutsche Forschungsgemeinschaft.     

A Green's Function Approach to the Shift of Spectral Lines in Dense Plasmas

Variations of the spectral lines in high dense ion plasmas with temperature and pressure may be characterized by the broadening as well as by the shift of spectral lines. For dense hydrogen- and alkali-plasmas (free carrier density larger than 10¹⁶/cm³) one of the possible mechanisms responsible for line profiles is considered to be the Coulomb interaction with free charged carriers. Using thermodynamic Green's functions, a systematic approach to the theory of spectral lines starting from the complex dielectric function is outlined. The line shift is derived from a perturbative treatment of the two-particle Green's function in the surrounding plasma. The shift of several lines proportional to the carrier density is evaluated as a function of the temperature and compared with experimental results.     

Ein Satz über geodätische Verbindbarkeit in normalhyperbolischen Räumen

Under certain conditions, two points of a normal hyperbolic manifold joined by a time-like curve can be joined by a time-like geodesic. These conditions are discussed, and some applications are given.