Köln 2004 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 2: Nuclear Structure/Spectroscopy I

HK 2.6: Talk

Monday, March 8, 2004, 17:45–18:00, A

Half-life measurements of fully-ionized ²⁰⁷Tl atoms — •D. Boutin¹, L. Maier², T. Yamaguchi^1,3, F. Bosch¹, C. Scheidenberger¹, K. Beckert¹, P. Beller¹, T. Faestermann², B. Franczak¹, H. Geissel^1,4, E. Kaza¹, P. Kienle², O. Klepper¹, C. Kozhuharov¹, Yu.A. Litvinov¹, M. Matos¹, G. Münzenberg^1,5, F. Nolden¹, Yu.N. Novikov⁶, T. Ohtsubo⁷, W. Plass⁴, M. Portillo¹, V. Shishkin¹, J. Stadlmann¹, M. Steck¹, K. Takahashi⁸, H. Weick¹, and M. Winkler¹ — ¹GSI Darmstadt — ²TU München — ³Saitama University — ⁴JLU Giessen — ⁵JGU Mainz — ⁶PNPI St Peterburg — ⁷Niigata University — ⁸MPIK Heidelberg

For the understanding of the nucleosynthesis in stars, radioactive decays play an important role. However in the stellar medium the extreme temperatures and pressures lead to the stripping of most of the electrons from the atoms, which can lead to a dramatic change in their β-decay probabilities. In particular in highly-ionized atoms the bound-β⁻ channel opens up .

Half-life measurements of fully-ionized ²⁰⁷Tl⁸¹⁺ were performed with time-resolved Schottky Mass Spectrometry (SMS) at the FRS-ESR facility in GSI. The acceptance of the Experimental Storage Ring (ESR) allowed to observe both the continuum-β⁻ decay (to ²⁰⁷Pb⁸²⁺) and bound-β⁻ decay (to ²⁰⁷Pb⁸¹⁺) of this nuclide, and consequently to evaluate the partial half-lives and the branching ratios. The isomeric state of fully-ionized ²⁰⁷Tl (T_1/2 = 1.33 s for the neutral atom) and its decay to the ground state could be also observed. The experimental results will be discussed and compared with theoretical predictions.