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Neutron star (NS) merger ejecta offer a viable site for the production ofheavy r-process elements with nuclear mass numbers A >140. The crucial role offission recycling is responsible for the robustness of this site against manyastrophysical uncertainties. Here, we introduce new improvements to ourscission-point model, called SPY, to derive the fission fragment distributionfor all neutron-rich fissioning nuclei of relevance in r-process calculations.These improvements include a phenomenological modification of the scissiondistance and a smoothing procedure of the distribution. Such corrections leadto a much better agreement with experimental fission yields. Those yields arealso used to estimate the number of neutrons emitted by the excited fragmentson the basis of different neutron evaporation models. Our new fission yieldsare extensively compared to those predicted by the so-called GEF model. Theimpact of fission on the r-process nucleosynthesis in binary neutron mergers isalso reanalyzed. Two scenarios are considered, the first one with low initialelectron fraction is subject to intense fission recycling, in contrast to thesecond one which includes weak interactions on nucleons. The various regions ofthe nuclear chart responsible for fission recycling during the neutronirradiation as well as after freeze-out are discussed. The contribution fissionprocesses may have to the final abundance distribution is also studied indetail in the light of newly defined quantitative indicators describing thefission recycling, the fission seeds and the fission progenitors. Inparticular, those allow us to estimate the contribution of fission to the finalabundance distribution stemming from specific heavy nuclei. Calculationsobtained with SPY and GEF fission fragment distributions are compared for bothr-process scenarios.

Fission fragment distributions and their impact on the r-process nucleosynthesis in neutron star mergers