  Neutron star (NS) merger ejecta offer a viable site for the production of
heavy r-process elements with nuclear mass numbers A >140. The crucial role of
fission recycling is responsible for the robustness of this site against many
astrophysical uncertainties. Here, we introduce new improvements to our
scission-point model, called SPY, to derive the fission fragment distribution
for all neutron-rich fissioning nuclei of relevance in r-process calculations.
These improvements include a phenomenological modification of the scission
distance and a smoothing procedure of the distribution. Such corrections lead
to a much better agreement with experimental fission yields. Those yields are
also used to estimate the number of neutrons emitted by the excited fragments
on the basis of different neutron evaporation models. Our new fission yields
are extensively compared to those predicted by the so-called GEF model. The
impact of fission on the r-process nucleosynthesis in binary neutron mergers is
also reanalyzed. Two scenarios are considered, the first one with low initial
electron fraction is subject to intense fission recycling, in contrast to the
second one which includes weak interactions on nucleons. The various regions of
the nuclear chart responsible for fission recycling during the neutron
irradiation as well as after freeze-out are discussed. The contribution fission
processes may have to the final abundance distribution is also studied in
detail in the light of newly defined quantitative indicators describing the
fission recycling, the fission seeds and the fission progenitors. In
particular, those allow us to estimate the contribution of fission to the final
abundance distribution stemming from specific heavy nuclei. Calculations
obtained with SPY and GEF fission fragment distributions are compared for both
r-process scenarios.
