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Abstract: An accurate knowledge of the neutron capture cross sections of 62,63Ni iscrucial since both isotopes take key positions which affect the whole reactionflow in the weak s process up to A=90. No experimental value for the63Nin,gamma cross section exists so far, and until recently the experimentalvalues for 62Nin,gamma at stellar temperatures kT=30 keV ranged between 12and 37 mb. This latter discrepancy could now be solved by two activations withfollowing AMS using the GAMS setup at the Munich tandem accelerator which arealso in perfect agreement with a recent time-of-flight measurement. Theresulting preliminary Maxwellian cross section at kT=30 keV was determined tobe 30keV = 23.4 +- 4.6 mb. Additionally, we have measured the64Nigamma,n63Ni cross section close to threshold. Photoactivations at 13.5MeV, 11.4 MeV and 10.3 MeV were carried out with the ELBE accelerator atForschungszentrum Dresden-Rossendorf. A first AMS measurement of the sampleactivated at 13.5 MeV revealed a cross section smaller by more than a factor of2 compared to NON-SMOKER predictions.

Autor: I. Dillmann, T. Faestermann, G. Korschinek, J. Lachner, M. Maiti, M. Poutivtsev, G. Rugel, S. Walter, F. Käppeler, M. Erhard, A.


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