The regime of competing nuclear reactions in weak r-process

Sensitivity study of nuclear properties, particularly given that most remain experimentally unmeasured, is critical for understanding nucleosynthesis processes. Because it both reveals the features of the elements evolution and provides the valuable guidance to experiment. In the weak rapid neutron capture process, the (α,n) reactions are predicted to play dominated roles while the neutron capture reactions are suppressed due to insufficient neutron exposure. A number of measurements on the cross sections of (α,n) reactions are performed with various techniques subsequently. Measurements employing short-lived beams are particularly significant for understanding the weak r-process, since the nucleosynthesis path lies far from the valley of stability. However, the beam energy, which is directly corresponds to the astrophysical temperature, are not easily varied during the experiment especially when detection relies on γ-ray or neutron. Therefore, it would be highly instructive for energy setting if the temperature ranges of maximum sensitivity could be determined prior to the experiment. In this work, a sensitivity study,which focuses on the steps of the reaction flow, is proposed. It monitors the reaction rate of each type of reactions and the density of relevant nuclei which participate in, then determines the order of importance of nuclear reactions. The leading role of the (α,n) reaction is confirmed by this method, and the sensitive temperature ranges of all key reactions are then tabulated. Several characteristics found in this study are also discussed, including the upbend of matter flow at closed shells and the correlation between nuclear properties and the model trajectory.