Erlangen 2018 – scientific programme

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P: Fachverband Plasmaphysik

P 14: Astrophysical Plasmas - Poster

P 14.2: Poster

Tuesday, March 6, 2018, 16:15–18:15, Redoutensaal

Nuclear excitation by electron capture in astrophysical plasmas — •Yuanbin Wu, Hyoyin Gan, Christoph H. Keitel, and Adriana Pálffy — Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany

In hot and dense stellar plasmas in which the slow neutron capture nucleosynthesis takes place, nuclei may not be only in their ground states but also in long-lived excited states (isomers). So far studies on the thermal equilibrium of the ground and excited or isomeric nuclear states typically rely on detailed balance. In the astrophysical plasma, high charge states are available, and the timescale of collisional ionizations and photoionization is expected to be much shorter than the one of ionization by internal conversion (IC). The inverse process of IC, nuclear excitation by electron capture (NEEC) [1,2], in such plasmas is therefore not always accompanied by its detailed-balance counterpart due to the loss of the recombined electrons via fast atomic processes. Thus, the isomers might not be thermally equilibrated with the nuclear ground states. We study here the depletion of isomeric states through NEEC in dense stellar plasmas under the s-process environments. The results show that the NEEC rates for the depletion of the isomeric states ^124mSb and ^152mEu should be large, leading to isomer populations significantly different from what is expected via thermodynamic equilibrium.

[1] J. Gunst, Y. A. Litvinov, C. H. Keitel, and A. Pálffy, Phys. Rev. Lett. 112, 082501 (2014).

[2] Y. Wu, J. Gunst, C. H. Keitel, and A. Pálffy, arXiv: 1708.04826.