München 2006 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 51: Kern- und Teilchen-Astrophysik
HK 51.1: Vortrag
Donnerstag, 23. März 2006, 17:00–17:15, E
Neutron studies on hafnium: s abundances and r residuals — •Franz Käppeler1, Saed Dababneh1, Iris Dillmann1, Michael Heil1, Friedrich Voss1, Nicolas Winckler1, Klaus Wisshak1, Christoph Vockenhuber2, Walter Kutschera3, Anton Wallner3, Max Bichler4, Leonid Kazakov5, Frantisek Bečvář6, Milan Krtička6, Roberto Gallino7, and Marco Pignatari7 — 1Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany — 2TRIUMF, 4004 Wesbrook Mall, Vancouver, Canada — 3Universität Wien, A-1090 Wien, Austria — 4Atominstitut der Österreichischen Universitäten, A-1020 Wien, Austria — 5IPPE Obninsk, Kaluga-Region, Russia — 6Charles University, CZ-180 00 Prague, Czech Republic — 7Università di Torino and Sezione INFN di Torino, I-10125 Torino, Italy
The stellar (n, γ) cross sections of the stable Hf isotopes have been determined by comprehensive time-of-flight measurements with the Karlsruhe 4π Barium Fluoride Detector. These results were obtained with uncertainties between 0.9% and 2.6%, five times smaller than in previous experiments. Partial cross sections to ground and isomeric states could be experimentally identified for neutron capture on 176,177,178,179Hf, indicating a strong population of yet unknown isomeric states in 177Hf and 180Hf. Additional measurements were carried out via activation on 174Hf and on the unstable isotope 182Hf in a quasi-stellar neutron spectrum for kT = 25 keV. Based on these results the implications arising from the improved separation of the solar s- and r-process components are discussed.