Phenomenological level density model with hybrid parameterization of deformed and spherical state densities

A phenomenological level density model that has different level density parameter sets for the state densities of the deformed and the spherical states and the optimization of the parameters using experimental data of the average s-wave neutron resonance spacing are presented. The transition to the spherical state from the deformed one is described using the parameters derived from a microscopic nuclear structure calculation. The nuclear reaction calculation has been performed by the statistical model using the present level density. Resulting cross sections for various reactions with the spherical, deformed, and transitional target nuclei show a good agreement with the experimental data, which indicates the effectiveness of the present model. The role of the rotational collective enhancement in the calculations of those cross sections is also discussed. (author)