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  • 1
    ISSN: 1432-2234
    Schlagwort(e): INDO method for lanthanides ; Lanthanide halides ; Ce(NO3)6 2−
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An intermediate neglect of differential overlap method of use for examining the electronic structure of lanthanide complexes is developed. It is characterized by a basis set obtained from relativistic Dirac-Fock atomic calculations, the inclusion of all one-center two-electron integrals, and a parameter set based on molecular geometry. Lanthanide halides MX2, MX3 and MX4 are studied here, as well as initial results for the twelve coordinate Ce(NO3)6 −2 ion. Geometries obtained are in excellent agreement with experimental values when available. Many MX3 complexes are found to be pyramidal, and EuCl2 and YbCl2 are calculated to be bent even at the SCF level. Models invoking London type forces are therefore not required. Ionization potentials are calculated for the trihalides (δSCF) and are in reasonable agreement with experiment. Contrary to conclusion of others, f-orbital participation, although small, is required — at least in this model — to obtain the spread of metal to halide bond distance observed in these complexes. However f-orbital participation does not seem to be significant even in the twelve coordinate Ce(NO3)6 −2 complex: rather the large coordination number seems to be a consequence of the relatively large size of the lanthanide ion.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical chemistry accounts 81 (1992), S. 201-222 
    ISSN: 1432-2234
    Schlagwort(e): INDO method for lanthanides ; Spin-orbit interaction ; Electronic spectra ; Lanthanide monoxides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The Intermediate Nelgect of Differential Overlap model for spectroscopy has been extended to lanthanide complexes by including spin-orbit coupling. The method uses atomic spectroscopy and model Dirac-Fock calculations on the lanthanide atoms and ions to obtain ionization potentials, Slater-Condon factors and basis sets. The spin-orbit interaction strength, ζ(nl), is acquired from atomic spectroscopy, and only one-center terms are formally included. Calculation then proceeds using one open-shell operator for all sevenf-orbitals initially assumed degenerate to generate starting non-relativistic molecular orbitals for the subsequent configuration-interaction and spin-orbit calculation. Calculations are performed on the monoxides La, Ce, Gd, and Lu where there are ample experimental assignments. In general, the results are quite good, suggesting that the calculated energies, oscillator strengths and spin-orbit splittings can be used with success in assigning spectra, even in those cases wherejj-coupling is of intermediate strength.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Vegetation history and archaeobotany 8 (1999), S. 105-112 
    ISSN: 1617-6278
    Schlagwort(e): Honey ; Pollen analysis ; La Tène ; Iron Age ; Land-use history ; Biodiversity ; Southern Germany
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Klassische Archäologie , Biologie
    Notizen: Abstract Organic contents of bronze vessels from royal burial sites dating to the Iron Age in southern Germany were investigated by pollen analysis. All pollen assemblages observed were dominated by non-arboreal pollen of non-wind pollinated species, a characteristic feature of honey. On the basis of investigations on recent honey, estimates of the original amounts of honey present were made. It is suggested that two of the vessels were filled with a freshly prepared, highly concentrated mead, while a third contained possibly a mead or a beverage sweetened by honey. The high diversity of the pollen assemblages differs from recent honeys and points to a high biodiversity in the Iron Age landscapes, but also to the use of honey mixtures that originate from a large area that included the surrounding uplands. Records for several exotic pollen also support this hypothesis. At the Glauberg site, a honey-source area of more than 50-km radius is probable. This corresponds quite well with the average distance between known Celtic centres in central Europe, which is ca. 100 km.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Vegetation history and archaeobotany 9 (2000), S. 205-218 
    ISSN: 1617-6278
    Schlagwort(e): Human impact ; Prehistory ; Historical period ; Pollen analysis ; Black Forest
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Klassische Archäologie , Biologie
    Notizen: Abstract A detailed,14C-dated, pollen profile from Steerenmoos, a raised bog in the uplands of the southern Black Forest (Schwarzwald) is presented. The Late-glacial and early Holocene vegetation history conforms to the known pattern of forest dynamics for that region. At ca. 6100 cal. B.P.,Abies replaced the mixed oak forest, which is in contrast to adjacent regions whereFagus spread beforeAbies. From the Subboreal onwards,Fagus expanded and slowly largely replacedAbies. The mire developed from a fen to a raised bog. The mountain pine (Pinus mugo ssp.rotundata) on the present-day bog surface is a result of medieval burning. Cereal pollen are first recorded in the Neolithic (7600 cal. B.P.) and there is a closed curve forPlantago Lanceolata — a good indicator of human impact — since the Bronze Age (4000 cal. B.P.). On the basis of the cereal pollen record nine human impact phases (HIP) are described. HIP 1 and 2, which are short, date to ca. 7600 and 6700 cal. B.P., respectively, in a mixed oak forest context and are characterized by declines inCorylus, Tilia, Ulmus and bySalix (but no major deforestation) and peaks in charcoal and loss-on-ignition curves. HIP 3 and 4, which are short and weak, date to ca. 6000 and 5300 cal. B.P., respectively, and occur in the context of anAbies alba forest. The Bronze Age and Iron Age HIPs 5-7 are more intense and of longer duration than the Neolithic phases and result in a decline inAbies and an increase inFagus. The early medieval HIP 8, although rather weak, probably finds expression also in an archaeological artefact, namely a dug-out boat from the near-by Schluchsee. Finally, the late Medieval HIP 9 resulted in a major transformation in the landscape. It is argued that the earlier HIPs are not a reflection of distant events in the lowland valleys of the Rhine, Danube or Neckar but reflect more or less local developments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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