Realistic Partial State Densities for Proton-Neutron Configurations in Nuclei near Closed Shells

Abstract

Using Nilsson single-particle level schemes as input, we have calculated partial state densities for excited proton-neutron configurations with specified particle-hole numbers. The recursion relation method used is general and free of any mathematical approximations. Results are given for nuclides in the Sn region and for several Pb isotopes. The strong shell effects in these nuclei are clearly reflected in their state densities. The results are compared to densities obtained from the equidistant-spacing model. This model not only fails completely at low excitation energies as expected, but it also disagrees in several cases with the average behavior of the realistic densities at higher energies.