PHENOMENOLOGICAL STATISTICAL-ANALYSIS OF LEVEL DENSITIES, DECAY WIDTHS AND LIFETIMES OF EXCITED NUCLEI

All existing data on the level densities, decay widths and lifetimes of excited nuclei have been analyzed in the framework of the statistical model in order to better determine the parameters of the phenomenological systematics of the nuclear level density. Data on level densities of several hundred nuclides obtained in the excitation energy range from 2 up to 20 MeV were used. The level densities of nuclei with large deformation (at the saddle point) have been studied by analyzing the data on the neutron emission and fission partial width ratio GAMMA(n)/GAMMA(f), and the values of the fission barrier heights B(f), the level density parameters ratio a(f)/a(n) and the saddle point shell corrections delta-W(s.p.) have been extracted. The influence of shell and collective effects on the level density and the decay widths of nuclei which have different excitation energies and deformations has been studied.