EuNPC2015

In astrophysics, the rates of neutron-capture reactions in r and s processes are proportional to the nuclear level densities (NLD) and are important in the synthesis of elements heavier than iron. The most abundant isotope of iron, 56Fe, originates from an unstable isotope of nickel, 56Ni. This isotope is produced in supernovae and decays first to Cobalt and then to iron. Still the question of existence of 56Fe than 62Ni in supernovae is unanswered, even though the mean binding energy difference is of no importance to the theory of supernovae. Truran et al., favoured 56Fe has the highest BE/A, but Clifford and Taylor are the first to identify 62Ni has the highest mean binding energy. In this work we tried to answer the reason for the existence of 56Fe than 62Ni in supernovae remnants in the context of excitation energy, level density and thermal fluctuation, etc. The binding energy per nucleon in the mass region A=50-64 using Droplet model mass formula is calculated and found the nuclei 58Fe(8.76681MeV) and 62Ni(8.76789MeV) are strongly bound than 56Fe(8.74831MeV), which is in correlation with Fewell. The level density parameter (ldp) is determined, under statistical assumptions, by the relation between excitation energy and entropy. Nuclear structure effects upon the ldp can be considered by the inclusion of shell corrections, pairing correlations and collective excitations. The interrelation between structure and rotational effects in the stability of 56Fe is also discussed.