Sudden interchannel interaction in the Tl 6p ionization above the 5d threshold

The linear magnetic dichroism in the angular distribution of Tl 5d and 6p photoelectrons and their dynamical spin polarization have been measured between hnu = 30 and 50 eV. In contrast to the Xe 5p photoionization at the 4d threshold, our results show that above the Tl 5d threshold strong interchannel coupling effects induce a sudden increase in the asymptotic phase difference of the s and d waves for the Tl 6p ionization. This shows that the valence excitation is different for resonant (Xe 4d) and nonresonant (Tl 5d) excitation from subvalence shells.     

Untersuchung von Honig

Ohne Zusammenfassung     

Specifically deuteriated intermediates for the synthesis of liquid crystals and liquid-crystalline polymers

The recent developments in solid state N.M.R. techniques have rendered deuterium a most attractive nucleus for use in the study of liquid crystals and other ordered systems. Its application often requires that the deuterium be positioned at specific sites in the molecule. Here, the preparation of such specifically labelled compounds for use in liquid crystal research is discussed. It is shown that many deuteriated liquid crystals can be prepared from a limited set of labelled intermediates. Strategies for the labelling of such intermediates in both aromatic and aliphatic sites based on experience gained in the author's laboratory during the last years are discussed. In the experimental section more than fifty procedures for obtaining specifically deuteriated intermediates and mesogens are described in detail.     

Erste Ergebnisse einer Ringanalyse zur Erstellung eines internen Buchenblatt-Referenzmaterials für ?kosystemuntersuchungen

Summary To evaluate pollution effects on ecosystems, more and more plant and animal samples are analyzed for their concentrations of pollutants and nutrient elements. Since chemical analyses of biological materials are largely influenced by matrix effects, their accuracy depends on the availability of reference materials. Unfortunately only very few such standards exist so far. The described interlaboratory comparison of beech leaves from Baden-Württemberg demonstrates the possibility of producing reference materials from selected organisms, which — though not certified — are sufficient for research projects. Apart from their function as reference materials, those standards show typical levels of elemental concentrations for their region of origin. First results are introduced.