Potential signatures of fission in the r-process

Nicole Vassh (Hosted by Piarulli), University of Notre Dame

In very neutron-rich conditions, as can be found in neutron star merger environments, the r-process can synthesize up to the heaviest, most unstable nuclei, the actinides. If populated in such environments, actinide nuclei fission quickly to deposit daughter products back into lighter element regions such as the lanthanides. Understanding the effects of fission the r-process requires knowledge of fission properties for hundreds of nuclei on the neutron-rich side of stability, about which little is experimentally known. The aim to pinpoint whether fission is indeed occurring in r-process scenarios, thereby impacting lanthanide element abundances, is of particular interest following the observations of the electromagnetic counterpart for the GW170817 neutron star merger event which strongly implied the presence of lanthanide species. However, it is important to note that presently there is no evidence that this event produced elements heavier than the lanthanides such as gold, platinum, and beyond, which includes the actinides. Since nuclear fission is an especially exotic and energetic process, we will discuss ways in which the presence of fission may lead to observable signatures in astrophysical scenarios, thereby confirming the production of the heaviest r-process elements. We will also explore the potential for future experimental and theoretical efforts to refine our knowledge of fission in the r-process. The question of where nature primarily produces the heavy elements can only be answered through such collaborative efforts between experiment, observation, and theory.