Microscopic Description of Fission for the r-Process in Neutron Star Mergers
291
Fig. 4 (Color online) Systematics in the (N, Z) plane of the peak multiplicity in the isobaric yields
for some 2000 nuclei for an initial excitation energy of Q = 8 MeV
The transition between symmetric to asymmetric fission and the asymmetric fission
mode of some nuclei are complex problems which have been extensively studied
for the last decades, especially since the discovery of the mass asymmetry feature
characterizing the U fission. It remains an open problem which has been mainly
studied from different aspects, in particular considering the saddle or scission points
configuration of the fissioning system.
A doubly asymmetric fission (4 peaks) is still predicted (yellow region in Fig. 4).
These nuclei play a key role in explaining the origin of the rare-earth elements (A
165) during the r-process nucleosynthesis occurring in collapsing neutron stars [2].
Our new SPY2 version of the model confirms the conclusions of Ref. [2].
4 Conclusion
LEP and LAP have been obtained for a large number of even–even nuclei using
Gogny D1M PES. The fission barriers deduced from LEP are in good agreement
with evaluated data. Spontaneous fission half-lives deduced from LAP fairly well
reproduced experimental data, though the predictions remain very sensitive to the
excitation energy of the fissioning nucleus. It is planned to extend the PES, LEP,
and LAP calculations systematically to odd-A and odd-odd nuclei.
The updated version of the SPY model is based on the mean-field proton density
at the scission neck and assumes that the Coulomb repulsion between nascent
291
Fig. 4 (Color online) Systematics in the (N, Z) plane of the peak multiplicity in the isobaric yields
for some 2000 nuclei for an initial excitation energy of Q = 8 MeV
The transition between symmetric to asymmetric fission and the asymmetric fission
mode of some nuclei are complex problems which have been extensively studied
for the last decades, especially since the discovery of the mass asymmetry feature
characterizing the U fission. It remains an open problem which has been mainly
studied from different aspects, in particular considering the saddle or scission points
configuration of the fissioning system.
A doubly asymmetric fission (4 peaks) is still predicted (yellow region in Fig. 4).
These nuclei play a key role in explaining the origin of the rare-earth elements (A
165) during the r-process nucleosynthesis occurring in collapsing neutron stars [2].
Our new SPY2 version of the model confirms the conclusions of Ref. [2].
4 Conclusion
LEP and LAP have been obtained for a large number of even–even nuclei using
Gogny D1M PES. The fission barriers deduced from LEP are in good agreement
with evaluated data. Spontaneous fission half-lives deduced from LAP fairly well
reproduced experimental data, though the predictions remain very sensitive to the
excitation energy of the fissioning nucleus. It is planned to extend the PES, LEP,
and LAP calculations systematically to odd-A and odd-odd nuclei.
The updated version of the SPY model is based on the mean-field proton density
at the scission neck and assumes that the Coulomb repulsion between nascent