Spin cutoff factor and level density for Ni59 from an analysis of compound nuclear reactions

The spin cutoff parameter for 59Ni has been studied from different types of experimental data, including neutron angular distributions from the 56Fe(α,n)59Ni reaction, spin of discrete levels, the level density from the proton evaporation spectrum of the 54Fe(6Li,p)59Ni reaction and neutron resonance spacing. Experimental data points were compared with calculations using models widely used in literature. It was found that the available empirical models overestimate data points in the energy region below the neutron separation energy, while microscopic calculations which take into account pairing correlations within Hartree-Fock +Bardeen-Cooper-Schrieffer approach are consistent with data. As a result, it confirmed earlier findings that pairing correlations play an important role and need to be taken into account when the spin cutoff parameter is calculated below the neutron separation energy.