Fission yield model for astrophysical use based on the four-dimensional Langevin model

Nuclear fission is expected to play an essential role in the r-process nucleosynthesis via the fission recycling process. However, the impact of the fission recycling process on the r-process is still unclear due to the ambiguity of the fission yields for nuclei far from the beta-stability line and superheavy nuclei. Our four-dimensional Langevin model can reproduce experimental nuclear fission properties, such as fission fragment mass distributions and total kinetic energies in a systematic manner including their sudden changes due to shell structure. Then we developed a phenomenological yield model for nuclei Z=92 to 122, ranging from neutron deficient to very neutron-rich ones, by fitting the fission fragment mass yield obtained by the Langevin model with five Gaussians. We use the charge distributions for each isobar based on a parametrization which we have evaluated based on thousands of experimental data for actinides, to obtain the fission yields in the form of (Z, N) distributions. What is unique here is the sudden change of the mass distribution from a 2-peak to 1-peak structure for the region of 256 Fm, and the appearance of a 5-peak structure for superheavy nuclei predicted by the 4D Langevin calculation.