Speaker
Description
Understanding how elements are formed in the universe requires a detailed knowledge of the nuclear reactions that govern nucleosynthesis. Particle capture and photo-absorption reactions are particularly important, as they compete to build up or dismantle nuclei in stellar and explosive environments. The probabilities of these reactions are governed by cross-sections, which in turn depend sensitively on the nuclear level density (NLD) and the structure of available excited states. Through their impact on reaction rates under astrophysical conditions, NLDs and cross-sections determine the balance between capture and photodisintegration, thereby shaping nucleosynthesis pathways and the resulting elemental abundances.
In nuclear astrophysics, the critical influence of the NLD on reaction rate calculations has been well established. However, the specific NLD energy range that has the greatest impact on the cross-section and reaction rate, respectively, still remains unclear. Within this work, the NLD energy regions that most significantly affect capture and photo-absorption reactions relevant to nucleosynthesis are analyzed. While previous studies have extensively investigated the sensitivity of reaction cross-sections to variations in the photon strength function, a systematic analysis of cross-section and reaction-rate sensitivities to the NLD over different energy ranges is performed. This study employs microscopic NLDs derived from the Hartree–Fock–Bogoliubov plus combinatorial approach within the Hauser-Feshbach framework to quantify the impact of NLD variations on calculated observables.
In addition, the microscopic NLD is compared with experimentally extracted NLDs obtained using the Oslo method for the 120Sn(n,γ)121Sn reaction. The presence of significant uncertainties in the experimental data within the energy range that contributes most strongly to the calculated observables highlights the need for further experimental and theoretical investigations. Improved constraints in this energy range are expected to provide valuable input for refining nuclear models and guiding future measurements, especially those targeting level schemes at moderate excitation energies.
