The 154Gd neutron capture cross section measured at the n_TOF facility and its astrophysical implications

Abstract

The (n, γ) cross sections of the gadolinium isotopes play an important role in the study of the stellar nucleosynthesis. In particular, among the isotopes heavier than Fe, ¹⁵⁴Gd together with ¹⁵²Gd have the peculiarity to be mainly produced by the slow capture process, the so-called s-process, since they are shielded against the β-decay chains from the r-process region by their stable samarium isobars. Such a quasi pure s-process origin makes them crucial for testing the robustness of stellar models in galactic chemical evolution (GCE). According to recent models, the ¹⁵⁴Gd and ¹⁵²Gd abundances are expected to be 15-20% lower than the reference un-branched s-process ¹⁵⁰Sm isotope. The close correlation between stellar abundances and neutron capture cross sections prompted for an accurate measurement of ¹⁵⁴Gd cross section in order to reduce the uncertainty attributable to nuclear physics input and eventually rule out one of the possible causes of present discrepancies between observation and model predictions. To this end, the neutron capture cross section of ¹⁵⁴Gd was measured in a wide neutron energy range (from thermal up to some keV) with high resolution in the first experimental area of the neutron time-of-flight facility n_TOF (EAR1) at CERN. In this contribution, after a brief description of the motivation and of the experimental setup used in the measurement, the preliminary results of the ¹⁵⁴Gd neutron capture reaction as well as their astrophysical implications are presented.