Stuttgart 2012 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 23: Poster: Electron scattering and recombination

A 23.4: Poster

Dienstag, 13. März 2012, 16:30–19:00, Poster.V

Nuclear Excitation by Electron Capture in Stellar Environments — •Stephan Helmrich, Katja Beckerle, and Adriana Pálffy — Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany

In the resonant process of nuclear excitation by electron capture (NEEC), the recombination of a continuum electron leads to the excitation of the nucleus [1]. NEEC becomes increasingly efficient with rising electron density and degree of ionization of the atoms involved. These are the predominant conditions in the interior of stars and supernovae. In the context of isomer depletion, NEEC populating low-lying nuclear excited states under dense stellar plasma conditions has been investigated [2].

In the present work we consider for the first time NEEC built on highly excited states close to the neutron threshold prior to their decay. Neutron capture and successive gamma decay followed by beta decay of the thus formed neutron-rich daughter nucleus constitutes the basic reaction leading to the synthesis of heavy isotopes. We show that even low-energetic NEEC on the order of tens of keV following neutron capture may significantly change the net decay rates of the formed compound nucleus. Thus, neutron re-emission becomes predominant at the expense of gamma decay, significantly suppressing the production of the daughter isotope.

[1] A. Pálffy, W. Scheid and Z. Harman, Phys. Rev. A 73, 012715 (2006).

[2] G. Gosselin, P. Morel and P. Mohr, Phys. Rev. C 81, 055808 (2010).