Understanding heavy element nucleosynthesis through experiments with radioactive isotope beams

The rapid neutron capture process (r-process) in neutron-rich astrophysical environments is the main production mechanism for the heaviest elements found in nature. A better understanding of how the r-process synthesizes heavy elements has emerged thanks to a wealth of astronomical observations, in the form of stellar spectroscopy data and multi-messenger observations of merger events, together with improved astrophysical models. These point to an intriguing history of galactic chemical evolution involving contributions from processes at a range of neutron richness and a variety of stellar sites, including different types of supernova and compact object mergers. The r-process is driven by nuclear reactions on very unstable isotopes, whose properties are not well understood because of the large asymmetry in their number of neutrons and protons. The structure properties of r-process isotopes have a strong imprint in the nucleosynthesis, so nuclear physics uncertainties are still a significant limitation to understand in detail the complexities of the production heavy elements. I will discuss how a new generation of nuclear physics accelerator laboratories, such as the Facility for Rare Isotope Beams, have made it possible to measure the nuclear properties of r-process isotopes and place strong constraints on the predictions of astrophysical models. I will focus on recent measurements of masses and beta-decay of isotopes in the mid-shell region between N=50 and N=82, relevant to weak r-process nucleosynthesis, and in the N=126 region that acts as a gateway for the nucleosynthesis of the actinides.