Bonn 2010 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 55: Nukleare Astrophysik III

HK 55.1: Group Report

Thursday, March 18, 2010, 16:30–17:00, HG VI

Experimental constraints on the stellar ⁶³Ni(n,γ)⁶⁴Ni cross section — •Iris Dillmann — Physik Department E12 und Excellence Cluster Universe, TU München

⁶³Ni (t_1/2=101 y) is an important branching point in the weak s-process flow, but experimental information is still missing for the ⁶³Ni(n,γ) as well as for the inverse ⁶⁴Ni(γ,n) reaction. We have measured the ⁶⁴Ni(γ,n)⁶³Ni cross section via photoactivation using bremsstrahlung at end-point energies of 10.3, 11.5, and 13.4 MeV from the ELBE facility in Dresden-Rossendorf followed by Accelerator Mass Spectrometry (AMS) at the MLL accelerator in Garching [1,2]. The irradiation at 13.4 MeV revealed a cross section which is lower by a factor of 2 compared to NON-SMOKER predictions. Calculations of s-process nucleosynthesis in massive stars showed that this change has no influence during core He burning and ⁶³Ni can decay to ⁶³Cu. However, with the higher temperatures and neutron densities during convective shell C burning this lower cross section will change strongly the final abundances of ⁶³Cu (+30%) and ⁶⁴Ni (−20%).

This research is supported by the DFG cluster of excellence "Origin and Structure of the Universe"

[1] Stephan Walter, Ph. D. thesis (Universität Karlsruhe) 2008.

[2] I. Dillmann et al., Nucl. Instr. and Meth. B (2009), doi: 10.1016/j.nimb.2009.10.153