Phenomenological nuclear level densities using the KTUY05 nuclear mass formula for applications off-stability

A new parametrization for the phenomenological nuclear level density taking account of the shell and pairing energies of the recent nuclear mass formula of Koura, Tachibana, Uno, and Yamada (KTUY05) is proposed. Such a level density formula is often required to calculate nuclear reaction cross sections for nuclei off-stability, especially for fission systems and astrophysical applications. With the phenomenological level density formula of Gilbert-Cameron with the energy dependent level density parameter of Ignatyuk, a smooth dependence of the asymptotic level density parameter a^* on the mass number is obtained. At low energies, systematics for the constant temperature model are also derived by connecting the Fermi gas level density and the discrete level information available for more than 1,000 nuclei. Some comparisons with the discrete level data and the microscopic model are made to validate our approach, and it is concluded that the parametrization obtained can be used for nuclear reaction calculations on stable or unstable nuclei within a reasonable uncertainty. (author)