Systematics of nuclear level density parameters

The level density parameters for backshifted Fermi gas (both without and with energy-dependent level density parameter) and constant-temperature models have been determined for 310 nuclei between F-18 and Cl-251(-) by fitting of the complete level schemes at low excitation energies and s-wave neutron resonance spacings at the neutron binding energies. Simple formulas are proposed for the description of the two parameters of each of these models, which involve only quantities available from the mass tables. These formulas may constitute a reliable tool for extrapolating to nuclei far from stability, where nuclear level densities cannot be measured.