Creation of heavy elements in neutron star mergers

Research Project, 2024 – 2027

The origin of the heaviest elements in the Universe has been a mystery for decades, until an event on August 17, 2017 gave us a first answer. Gravitational waves as well as astronomical observations, covering the entire electromagnetic spectrum, provided for the first-time data on the merging of two neutron stars into a black hole. This event is very much connected to the creation of heavy elements, as data indicate that the collision of two neutron stars results in a high flux of neutrons, which drives a complex network of nuclear reactions and decays, called the r-process (for rapid neutron capture process). In order to interpret emerging data from neutron-star mergers, it is important to understand the underlying nuclear physics processes. Nuclear fission is expected to play a key role in the r-process, which this project will investigate. Fission limits the mass of nuclei which can be formed during the r-process and the resulting fission fragments take again part in the reaction network. Within the duration of this project, we will exploit the unique capabilities of the  HIE-ISOLDE radioactive beam facility at CERN, to obtain high-precision data on prompt gamma-ray emission together with fission probabilities and fission fragment yields of heavy neutron-rich isotopes at the ISOLDE Solendoidal Spectrometer. All of those data are needed and will be used to model the creation of heavy elements in neutron-star mergers.