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

Abstract

The (n, gamma) 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, Gd-154 together with Gd-152 have the peculiarity to be mainly produced by the slow capture process, the so-called s-process, since they are shielded against the beta-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 Gd-154 and Gd-152 abundances are expected to be 15-20% lower than the reference un-branched s-process Sm-150 isotope. The close correlation between stellar abundances and neutron capture cross sections prompted for an accurate measurement of Gd-154 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 Gd-154 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 (EARL) 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 Gd-154 neutron capture reaction as well as their astrophysical implications are presented.