Nuclear Level Density within Extended Superfluid Model with Collective State Enhancement

Abstract

For nuclear level densities, an enhanced generalized superfluid model with different vibrational enhancement factors is studied. The ready-to-use tables for the asymptotic value of a-parameter of level density as well as for additional shift to excitation energy for 291 atomic nuclei are prepared using the chi-square fit of the theoretical values of neutron resonance spacing and cumulative number of low-energy levels to the experimental values. The systematics of these parameters as a function of mass number and neutron excess are obtained. The vibrational enhancement descriptions are additionally tested for a wide range of excitation energies. Simple methods of the vibrational enhancements lead to increasing the level density due to vibrational states by factor ∼ 2 to 3 for the isotopes A ∼ 100 with the excitation energies near the neutron binding energies.