The 139La(n,gamma) cross section: key for the onset of the s process

Abstract

The nuclear resonance parameters and the capture cross section of the neutron magic isotope 139La has been measured n_TOF. The description of the experimental apparata is followed by the data analysis procedures. We extracted the resonance parameters, the main nuclear quantities such as the resonance integral, the average gamma widths for s- and p-waves, the nuclear level densities and the neutron strength functions. These results represent a signifcant improvement over previous data. The deduced Maxwellian-averaged capture cross sections are important for the interpretation of the most recent spectroscopic observations in low metallicity stars.

50 pages and 9 Figures

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• ${}^{137,138,139}$La($n$, $\gamma$) cross sections constrained with statistical decay properties of ${}^{138,139,140}$La nuclei
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• Energy dependent angular distribution of individual $\gamma$-rays in the ${}^{139}$La($n$, $\gamma$)${}^{140}$La* reaction
• Neutron Capture Reactions near N=82 Shell-Closure
• Measurements of neutron total and capture cross sections of ${}^{139}$La and evaluation of resonance parameters