New half-lives in the polonium isotopic chain

The astrophysical rapid-neutron capture process (r-process) of explosive nucleosynthesis is responsible for the formation of half of the heavy nuclei above Fe. Actinides are produced towards the end of this process, when the neutron flux is expected to be minimal. Given that, in this heavy region of the chart of nuclides, the r-process path runs far away from the accessible species, experimental inputs on β decay for nuclei beyond N=126 are particularly useful to test predictions of global nuclear models. In this paper, results from a recent experiment performed by the HISPEC-DESPEC collaboration are discussed. The experiment populated 220<A<230 Po-Fr nuclei in a relativistic fragmentation reaction induced by a 1 GeV/u 238 U beam. The species were selected and identified using the FRagment Separator (FRS) and implanted in the DEcay SPECtroscopy (DESPEC) station to study their subsequent β decay. The β -decay half-lives in the polonium isotopic chain are discussed with the help of recent theoretical models, to assess the impact of the measured values on the predictions of the r-process.