Microscopic Fission Barriers of Very Heavy Nuclei

The fission barriers of sixteen isotopes of Californium, Fermium and Nobelium have been microscopically calculated up to and beyond the second saddle point within Hartree-Fock plus pairing approaches. The Skyrme density-dependent effective force in its SkM* parametrization - rather well suited to the description of fission barriers - was used in the particle-hole channel. As for the treatment of pairing correlations, two approaches have been followed: the first is the traditional HF plus BCS treatment with a seniority force, while the second makes use of a recently proposed method explicitly conserving the particle number and using a delta force for the particle-particle and hole-hole matrix elements. The energy correction due to the rotational zero-point motion has been approximately taken into account.