Fission is a new RIPL-2 segment, which retains the RIPL-1 recommendation and, in addition, includes global prescription for barriers and nuclear level densities at saddle points.

Fission barrier parameters for the trans-thorium nuclei were recommended by Maslov [5] and for the preactinides by Smirenkin [20]. The fission bar­rier parameters are strongly correlated with the corresponding level density description and the symmetry of the fission barriers should always be taken into account for the consistent description of the fission cross sections. For nuclei with Zj80 the liquid drop barriers described by Sierk’s code [21] are recommended with the addition of the ground-state shell corrections esti­mated by the Moeller-Nix (Segment 1) or the Mayer-Swiatecki (Segment 5) mass formulae. Sierk’s code provides fits to the fission barriers calculated using Yukawa-plus-exponential double folded nuclear energy, exact Coulomb diffuseness corrections, and diffuse-matter moments of inertia.

Another option is to predict the fission barriers and saddle point deforma­tions obtained within the Extended Thomas-Fermi plus Strutinsky Integral (ETFSI) method of Goriely. The ETFSI approach is a semi-classical ap­proximation to the Hartree-Fock method in which the shell corrections are calculated with the ’integral’ version of the Strutinsky theorem. BCS cor­rections are added with a delta-pairing force. Fission barriers are derived in terms of the SkSC4 Skyrme force on which the ETFSI-1 mass formula is based. Experimental primary barriers can be reproduced within plus or mi­nus 1.5 MeV (except for elements with Z < 87 which have barriers above 10

MeV). The present ETFSI compilation includes 2301 nuclei with 78<Z<120. Their masses range from slightly neutron deficient to very neutron rich nuclei (close to the calculated neutron drip line) up to A = 318. For each nucleus a maximum of two barriers are given (”inner” and ”outer”). In addition to these calculated barriers, the deformation parameters at the corresponding saddle points are also included. The nuclear shapes are limited to axially symmetrical deformations.

The ETFSI fission barriers are complemented with nuclear level densities (NLD) at the fission saddle points [22] for some 2300 nuclei with 78<Z<120. At each saddle point, the NLD is estimated within the statistical partition function approach. The NLD calculation is based on the realistic microscopic single-particle level scheme [11] determined by means of the HF-BCS mass model obtained with the MSk7 Skyrme force. For each saddle point, the single-particle level scheme is calculated consistently by the HF-BCS model constrained on the corresponding quadrupole, octupole and hexadecapole moments. The same pairing strength (within the constant-G approxima­tion) is used as for the NLD calculation at the ground-state equilibrium deformation (segment 5). No damping of the collective effects at increas­ing excitation energies is considered. The NLD for nuclei with left-right asymmetric fission barriers is increased by a factor of 2.