Maxwellian-Averaged Neutron Capture Cross-Sections and Thermonuclear Reaction Rates for 56,57,58Fe, 59Co, And 60Ni Isotopes at Astrophysical Energies

Initially-produced isotopes during the course of the s-process have a significant impact on the continuity and branching network of this process. Such isotopes can undergo various neutron capture mechanisms, of which (n, γ) is important. In this research, the direct, thermal, and Maxwellian-averaged cross section (MACS), as well as the astrophysical reaction rates of the radiative neutron-capture reactions, were calculated for ^56,57,58Fe, ⁵⁹Co, and ⁶⁰Ni isotopes. At kinetic energies between kT = 0.037 and 482.3 keV, corresponding to astrophysical temperature in the range of 0.01 to 1GK. E1 transitions of s-wave were considered with the approximations of direct non-resonant components. The obtained MACSs and hence reaction rates were based on the data from the major measured and evaluated nuclear libraries and tables and they showed very well agreements with the most recommended database and compilations. Moreover, the effect of the direct, thermal, and negative resonance cross sections on the MACS was found to be very small and exhibit a 1/v behavior overall temperatures, with a maximum at T = 0.01GK, while the main contribution attributed to the positive resonance term, that found to dominate overall temperature range. (paper)