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Helium burning of22Ne (1989)

Wolke, K. ; Harms, V. ; Becker, H. W. ; [et al.]

Springer

The European physical journal 334 (1989), S. 491-510

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ISSN: 1434-601X

Keywords: 25.55 ; 97.10

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The22Ne(α, γ)26Mg and22Ne(α, n)25Mg reactions were investigated forE α(lab) from 0.71 to 2.25 MeV. Neon gas enriched to 99% in22Ne was recirculated in a differentially pumped gas target system of the extended type. Theγ-ray transitions were observed with Ge(Li) detectors and the neutrons with3He ionization chambers. A previously known resonance at ER(lab)=2.05 MeV was verified and 15 new resonances were found in the energy range covered, with the lowest at ER(lab)=0.83 MeV. Information on resonance energies, widths, strengths,γ-ray branching ratios, as well asJ π assignments, is reported. The energy range investigated corresponds to the important temperature range ofT 9 from 0.3 to 1.4 (109 K), for which the astrophysical rates were determined for both reactions. The results show that the ratios of the rates for22Ne(α, n)25Mg and22Ne(α, γ)26Mg are significantly smaller than the previously adopted values, e.g., by at least a factor of 60 nearT 9=0.65. Thus, the22Ne(α, n)25Mg reaction will likely play a smaller role as a neutron source fors-process nucleosynthesis, than has frequently been assumed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01294757

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Synthese und Charakterisierung von Metallocen-Chelaten heterocyclischer 1,2-Dithiolate (1994)

Zeltner, S. ; Dietzsch, W. ; Olk, Ruth-Maria ; [et al.]

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 620 (1994), S. 1768-1776

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ISSN: 0044-2313

Keywords: Metallocene dichalcogenolene ; DNMR ; EPR, X-Ray ; Chemistry ; Inorganic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: Synthesis and Characterization of Metallocene Chelates of Heterocyclic 1,2-DithiolatesSynthesis and properties of metalocene dithiolene chelates Cp2ML with metal(IV) ions (M) of group IVA (Ti, Zr, Hf) and of vanadium with L = dmit (1,3-dithiole-2-thione-4,5-dithiolate), dmt (1,2-dithiole-3-thione-4,5-dithiolate), dmid (1,3-dithiole-2-one-4,5-dithiolate) and dmise (1,3-dithiole-2-selone-4,5-dithiolate) are described. The structures of these compounds were discussed using IR-, UV/VIS-, 1H-NMR-, 13C-NMR- and EPR data. The activation parameters of the chelate ring inversion of titanocene dithiolenes (Cp2TiL) and the x-ray structure of Cp2Ti(dmid) are given.

Notes: Synthese und Eigenschaften neuer Metallocen-Dithiolen-Chelate Cp2ML der Metall(IV)-Ionen (M = Ti, Zr, Hf) sowie des Vanadiums mit L = dmit (1,3-Dithiol-2-thion-4,5-dithiolat), dmt (1,2-Dithiol-3-thion-4,5-dithiolat), dmid (1,3-Dithiol-2-on-4,5-dithiolat) und dmise (1,3-Dithiol-2-selon-4,5-dithiolat) werden beschrieben. Die Strukturen der Verbindungen werden anhand der IR-, UV/VIS-, Massen-, 1H-NMR-, 13C-NMR- bzw. EPR-Spektren diskutiert. Die durch dynamische Kernresonanzspektroskopie bestimmten Aktivierungs-parameter der Chelatringinversion der Titanocen-Dithiolene (Cp2TiL), sowie die Röntgenkristallstrukturanalyse von Cp2Ti(dmid) werden vorgestellt.

Additional Material: 7 Ill.