Manifestation of pairing effects in the cross section of 238Pu fission induced by neutrons

Neutron-induced fission cross section of 238Pu (n, f) is described within a statistical model in the energy range of 1 keV up to ∼ 5 MeV. The stepwise structure appearing above the fission threshold (at the incident neutron energies E > 1 MeV) is interpreted as being due to a shoulder in the level density of the fissioning 239Pu nuclide at inner saddle deformation. The shoulder in the level density of the odd 239Pu nuclide is shown to be due to excitation of intrinsic one- and three-quasiparticle states. The level density is approximated introducing shell, pairing and collective effects