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HK: Fachverband Physik der Hadronen und Kerne

HK 24: Kern- und Teilchen-Astrophysik

HK 24.8: Talk

Tuesday, March 11, 2008, 13:15–13:30, 2B

Stellar (n,γ) cross section of proton-rich nuclei — •Justyna Marganiec^1,2, Iris Dillmann², Cesar Domingo Pardo², Peter Grabmayr³, and Franz Käppeler² — ¹Institute of Physics, University of Lodz, 90-236 Lodz, Poland — ²Institut für Kernphysik, Forschungszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany — ³Physikalisches Institut der Universität Tübingen, D-72076 Tübingen, Germany

The neutron capture cross sections of proton-rich nuclei are needed for nucleosynthesis studies of the heavy elements in the p process. In this process, (n,γ) reactions compete with (γ,n) reactions and play a secondary role in the freeze-out phase. So far, the neutron capture cross sections for several of these isotopes were not yet experimentally determined.

The present measurements were based on the activation technique. Neutrons were produced at the Karlsruhe Van de Graaff accelerator via the ⁷Li(p,n)⁷Be reaction. For proton energies just above threshold, one obtains a neutron spectrum similar to a Maxwellian distribution for kT = 25 keV. A set of samples was irradiated in this quasi-stellar neutron spectrum together with gold foils for normalization of the neutron flux. Results will be reported for isotopes of ¹⁶⁸Yb, ¹⁸⁰W, ¹⁹⁰Pt and ¹⁹⁶Hg. These values were obtained at kT = 25 keV and are extrapolated to lower and higher thermal energies.