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Resonant Nuclear Gamma Decay and the Heavy-Element Nucleosynthesis (gRESONANT)
Date du début: 1 mars 2015, Date de fin: 29 févr. 2020 PROJET  EN COURS 

THE GRAND CHALLENGE: The “Holy Grail” of nuclear astrophysics is to understand the astrophysical processes responsible for the formation of the elements. A particularly challenging part is the description of the heavy-element nucleosynthesis. The only way to build the majority of these heavy nuclides is via neutron-capture processes. Unaccounted-for nuclear structure effects may drastically change these rates. MAIN HYPOTHESIS: Nuclear low-energy gamma-decay resonances at high excitation energies will enhance the astrophysical neutron-capture reaction rates. NOVEL APPROACH: This proposal is, for the first time, addressing the M1 scissors resonance in deformed, neutron-rich nuclei and superheavy elements. A new experimental technique will be developed to determine the electromagnetic nature of the unexpected upbend enhancement. Further, s-process branch points for the Re-Os cosmochronology will be studied for the first time with the Oslo method.OBJECTIVES: 1) Measure s-process branch point nuclei with the Oslo method2) Radioactive-beam experiments for neutron-rich nuclei searching for the low-energy upbend and the M1 scissors resonance3) Develop new experimental technique to identify the upbend’s electromagnetic nature4) Superheavy-element experiments looking for the M1 scissors resonancePOTENTIAL IMPACT IN THE RESEARCH FIELD: This proposal will trigger a new direction of research, as there are no data on the low-energy gamma resonances neither on neutron-rich nor superheavy nuclei. Their presence may have profound implications for the astrophysical neutron-capture rates. Developing a new experimental technique to determine the electromagnetic character of the upbend is crucial to distinguish between two competing explanations of this phenomenon. Unknown neutron-capture cross sections will be estimated with a much better precision than prior to this project, and lead to a major leap forward in the field of nuclear astrophysics.