Shell effects on level density in near doubly magic nuclei

A simple model to describe the level density of nuclei near the doubly magic nucleus 208 Pb been developed. A doubly magic nucleus is considered as a two-fermion gas with an energy gap at the Fermi energy. This model explains both the low- and high-energy level density behaviour. The high-energy 1 behaviour is tested by analysing α-particle decay rates from excited nuclei. The arguments developed should be important in the analysis of fission data and of Monte Carlo calculations of direct nucleon emission.