Recombination measurements at low energies with Au49+,50+,51+ at the TSR

Recombination of Au⁴⁹⁺, Au⁵⁰⁺, and Au⁵¹⁺ ions has been studied at the TSR. With Au⁵⁰⁺ ions a storage lifetime of only 2 to 4 s was observed with the magnetically expanded electron beam of the cooler at a density of n_e = 10⁷ cm^-3. This short storage time is a consequence of the highest recombination rate coefficient ever observed with an atomic ion (1.8·10^-6 cm³ s^-1 at zero relative energy E_rel = 0 between electrons and ions). At about 30 meV a huge dielectronic recombination resonance is found with a record small width of only about 15 meV. Such resonances fortuitously occurring near E_rel=0 are probably the main reason for the enhanced recombination rates observed with Au⁵⁰⁺, with Pb⁵³⁺ (in a recent experiment at LEAR) as well as with other complex ions. For Au⁴⁹⁺ and Au⁵¹⁺ the recombination rates are smaller by an order of magnitude. This revised version was published online in August 2006 with corrections to the Cover Date.     

New bifunctional anion-exchange resins for nuclear waste treatment

Additional¹ bifunctional anion-exchange resins have been designed, synthesized and evaluated for their ability to take up Pu(IV) from nitric acid solutions. Bifunctionality is achieved by adding a second anion-exchange site to the pyridine nitrogen (also an anion-exchange site) of the base poly(4-vinylpyridine) resin. Previous work focused on the effect of varying the chemical properties of the added site along with the length of an alkylene ‘spacer’ between the two sites. Here we examine four new 3- and 4-picolyl derivatives which maintain more rigidly defined geometries between the two nitrogen cationic sites. These materials, which have the two anion-exchange sites separated by three and four carbons, respectively, exhibit lower overall Pu(IV) distribution coefficients than the corresponding N-alkylenepyridium derivatieves with more flexible spacers. Methylation of the second pyridium site results in a ca. 20% increase in the Pu(IV) distribution coefficients.     

Studies on the chemistry of O,N- and S,N-containing heterocycles. 4 . Investigations on the nucleophilic substitution of activated 1,5-benzothiazepines

The reaction of the activated 1,5-benzothiazepine 1a with various amines is studied. In contrast to the phenylsubstituted derivative 1b no ring contraction but nucleophilic substitution is observed. Two novel ring systems 8 and 9 are obtained by nitrosation of 3g and by reaction of 1a with anthranilic acid, respectively.     

Eine neue Synthese des Pyrrolo[3,2,1-hi]indol-Systems Studien zur Synthese von 1,4-Oxazinen, 1. Mitt

Reaction of diphenacylaniline (1) withPPA yields in dependence of reaction time the indole3 and the pyrroloindole4. The structures were established on the basis of spectroscopic methods. Action of LiAlH₄ on4 forms5 by hydrogenation of one double bond and cleavage of one pyrrole ring.

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Herrn Prof. Dr.F. Vieböck zum 75. Geburtstag gewidmet.     

Functionalized large ring crown ethers

Reactions of 3,6,9,12-tetraoxa-7-(benzyloxymethyl)-1,14-tetradecanediol with appropriate ditosylates followed by hydrogenolysis produce hydroxymethyl-27-crown-9 and hydroxy- methyl-30-crown-10. Alkali metal cation complexation by lipophilic dodecyl ether derivatives of these crowns is examined.     

Separation of metals by liquid surfactant membranes containing crown ether carboxylic acids

A water-in-oil-in-water emulsion liquid membrane system is used to transport alkali metal and alkaline earth cations from an external alkaline aqueous source phase through an organic membrane containing a crown ether carboxylic acid and into the internal acidic aqueous phase of the emulsion droplet. The influence of varying the crown ether carboxylic acid structure upon the selectivity and efficiency of competitive metal ion transport is examined.     

Measurement of field effects on dielectronic recombination of Si11+ ions

Cross sections for dielectronic recombination can be influenced by the presence of external electric fields in the electron--ion collision region. In most of the previous experiments with multiply charged ions such fields were present but unknown. Therefore, comparisons of experimental results with theoretical calculations were ambiguous: for obtaining best possible agreement, theory could use the field strength as a free parameter to adjust the calculated cross sections to the experiment. In recent measurements with 10 MeV/u Si¹¹⁺ ions stored in CRYRING, controlled external motional electric fields up to 183 V/cm were introduced in the electron cooler. Significant cross section enhancements were found for Rydberg states n > 20. This revised version was published online in August 2006 with corrections to the Cover Date.     

An investigation of short-lived isomers in the nuclei90,92Nb,99Mo,98,100,101Tc and101Ru

Short-lived isomers in the nuclei^90,92Nb,⁹⁹Mo,^98,100,101Tc and¹⁰¹Ru populated in photonuclear reactions were studied by pulsed beam techniques. Energy and half-life of theγ-rays deexciting the isomeric levels were measured by recording energy-time spectra. The delayedγ-rays andK X-rays were detected by means of an intrinsic Ge-detector of high resolution. From the measured intensity ratios internal conversion coefficients were determined. The multipolarities of the isomeric transitions could be deduced in most cases. A classification of the observed isomers has been tried on the basis of the obtained experimental results and most recent literature data.     

Theory of the Ionization Equilibrium in Dense Semiconductor Plasmas

The semiconductor is considered as a plasma of electrons, donors and occupied acceptors in a homogeneous medium interacting by Coulomb's law. The mass action law for the ionization equilibrium of electrons and donors is formulated taking into account the interaction of the charges. The lowering of the ionization energy is calculated using the quantum statistical method of binary density matrices. By comparision with the experimental results of Debye and Conwell for the lowering of the ionization energy good agreement between theory and experiment was found. The limit of stability of the semiconductor state is investigated.