Speaker
Justyna Marganiec
(GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany)
Description
The neutron capture cross sections of proton-rich nuclei are important for the nucleosynthesis of the heavy elements in the p process. Aspects of (n,gamma) reactions in the p process refer to the competition with (gamma,n) reactions, which affects the photodisintegration flux towards lighter nuclei, and to the formation of the final p-process abundances during the freeze-out phase. However, the knowledge of neutron capture cross sections of the rare proton-rich isotopes is very limited and still missing in many cases.
First measurements of the stellar neutron capture cross sections are reported for the stable p isotopes 168Yb, 184Os, and 196Hg. For 180W and 190Pt the uncertainties of 11% and 27% from previous easurements could be significantly reduced. 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. This quasi-stellar neutron spectrum allowed us to measure the Maxwellian averaged cross sections directly.
The experimental results were extrapolated from kT = 25 keV to lower and higher temperatures.
Author
Justyna Marganiec
(GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany)
Co-authors
C. Domingo-Pardo
(GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany)
F. Kaeppeler
(FORSCHUNGSZENTRUM KARLSRUHE, INSTITUT F¨UR KERNPHYSIK, 76344 EGGENSTEIN-LEOPOLDSHAFEN, GERMANY)
I. Dillmann
(Physik Department E12 and Excellence Cluster Universe, Technische Universitaet Muenchen, D-85748 Garching)
S. Walter
(FORSCHUNGSZENTRUM KARLSRUHE, INSTITUT F¨UR KERNPHYSIK, 76344 EGGENSTEIN-LEOPOLDSHAFEN, GERMANY)