Evidence for Nuclear Pairing Effects at the Fission Barrier

To determine the properties of nuclei as a function of nuclear deformation the (d,p) fission reaction for Pu /sup 239/ and U/sup 233/ is investigated at excitation energies just above the fission threshold where superfluidity eifects of the nuclear pairing are most in evidence, especially those effects that distinguish the finite, isolated nuclear superfluid from the infinite system. The results corroborate directiy the expected discontinuity in the spectrum at the onset of twoquasiparticle excitations and the increase in the energy gap over that occurring at stable deformations for Pu/sup 240/. They also evidence certain structure that is consistent with the existence of low-lying collective excitations at the fission barrier analogous to those observed at the stable shape. (C.E.S.)