First measurements of the total and partial stellar cross section to the $s$-process branching-point $^{79}$Se
| Autor: | Dillmann, I., Heil, M., Käppeler, F., Faestermann, T., Knie, K., Korschinek, G., Poutivtsev, M., Rugel, G., Wallner, A., Rauscher, T. |
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| Rok vydání: | 2008 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | 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 $\gamma$-ray transitions. The preliminary result for the total Maxwellian averaged cross section is $<\sigma>_{30 keV}$= 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 $\gamma$-spectroscopy and yielded $<\sigma>_{30 keV}$(part.)= 42.0$\pm$2.0 mbarn. Comment: Proceedings "Nuclei in the Cosmos" NIC- IX, June 25-30 2006, CERN, Geneva/ Switzerland, published with Proccedings of Science, PoS(NIC-IX)089 |
| Databáze: | arXiv |
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