Nucleosynthesis of nuclei heavier than iron and the role of the β-delayed neutron emission in the final element abundance. Experimental determination of neutron emission probabilities of exotic neutron-rich nuclei.

The main synthesis mechanisms of elements beyond iron is through the known neutron capture processes: slow (s) and rapid (r) neutron capture processes. They occur in different regions of the nuclear chart and they play a key role in the observed element abundances. In order to understand the nuclear physics involved, especially the case of the r-process, experimental properties of nuclei like β-decay half-lives, and β-delayed neutron emission probabilities (P_xn) need to be determined. These magnitudes are of interest for nuclear structure, astrophysics, and also for industrial and medical applications.

The scarce of experimental data in very the neutron-rich regions involved in the r-process is actually the main source of uncertainty of the astrophysical models to better understand the observed abundance distribution, since they rely heavily on theoretical data for yet unmeasured nuclei. The neutrons released during the decays of β-delayed neutron emitters in these regions play an important role in late phases of the r-process during the freeze-out by shifting decaying material to different mass chains and providing additional neutrons for further capture reactions.

Since 2016, the BRIKEN collaboration has investigated several neutron-rich regions between A=70 and A=200 with the aim of determining properties of hundreds of isotopes with unknown or incomplete decay information that were not accessible before. The experimental setup at the fragmentation RIB facility of RIKEN in Japan consisted of a DSSDs array to register the implanted ions and β-decays, and the BRIKEN neutron counter, which also included two HPGe clover-type γ-ray detectors for high resolution spectroscopy.

This contribution will also report experimental setup particularities and show data analysis techniques of the BRIKEN campaign.