Nuclear level densities in the mass range 4065

Nuclear level densities of interest over a large excitation energy range, as required in statistical model calculations, are investigated. A proper account of the nuclear level density has been obtained by the use of empirical back-shifted Fermi gas (BSFG), at medium excitation energies, and of realistic analytical formula with microscopic suggested parameters at the high excitation energies. The BSFG model parameters have been determined by a least-squares fit of recent experimental total numbers of the low-energy discrete levels and s-wave neutron resonance spacings. The necessary transition excitation range between the two different density approaches in the mass range 40<A<65 has been discussed. (authors)