Radiative Neutron Capture Reaction Rates for Nucleosynthesis: the Creation of the First R-Process Peak

In neutron star merger events, the occurrence of rapid neutron capture process (r-process) has been established. About half of the elements beyond iron are synthesised in stars by r-process. In stellar environments, very high neutron flux in a short time ( ∼ a few seconds) can be attained, leading to the creation of progressively neutron-rich nuclei until the waiting point is reached. At this point, further neutron capture reactions cannot happen and highly neutron-rich nuclei become stable via β ^- decay. A detailed understanding of the r-process remains illusive. In the present work, the theoretical predictions of radiative neutron capture (n, γ ) cross-sections of astrophysical importance and the reaction rates using the Hauser–Feshbach statistical model formalism have been investigated for Fe, Co, Ni, Cu, Zn, Ga, Ge, As and Se isotopes (around the first r-process peak near mass = 80 ). These calculations have been compared with the JINA REACLIB reaction rates. The inherent uncertainties remain large in neutron-rich nuclei. When there is low-energy enhancement, a significant increase in the reaction rate occurs for neutron capture.