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arXiv · 0806.2063

First measurements of the total and partial stellar cross section to the $s$-process branching-point $^{79}$Se

I. Dillmann·M. Heil·F. Käppeler·T. Faestermann·K. Knie·G. Korschinek·M. Poutivtsev·G. Rugel·A. Wallner·T. Rauscher
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Abstract

Although $^{79}$Se represents an important branching in the weak s process, the stellar neutron capture cross sections to this isotope have not yet been measured experimentally. In this case, experimental data is essential for evaluating the important branching in the s-process reaction path at $^{79}$Se. The total cross section of $^{78}$Se at a stellar energy of kT = 25 keV has been investigated with a combination of the activation technique and accelerator mass spectrometry (AMS), since offline decay counting is prohibitive due to the long terrestrial half life of $^{79}$Se (2.80$\pm$0.36 $\times10^5$ y) as well as the absence of suitable $γ$-ray transitions. The preliminary result for the total Maxwellian averaged cross section is $<σ>_{30 keV}$= 60.1$\pm$9.6 mbarn, significantly lower than the previous recommended value. In a second measurement, also the partial cross section to the 3.92 min-isomer was determined via $γ$-spectroscopy and yielded $<σ>_{30 keV}$(part.)= 42.0$\pm$2.0 mbarn.

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I. Dillmann, M. Heil, F. Käppeler, T. Faestermann, K. Knie, G. Korschinek, M. Poutivtsev, G. Rugel, A. Wallner, T. Rauscher. 2008-06-12. First measurements of the total and partial stellar cross section to the $s$-process branching-point $^{79}$Se. https://arxiv.org/abs/0806.2063

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