Structure of Nd 155 and Gd 163 from Cf 252 spontaneous fission

Background: A puzzle has arisen recently caused by the apparent shift in maximum deformation from the expected Dy66 isotopic chain to the 60Nd isotopic chain in the 82<N<126 and 50<Z<82 midshell region. Purpose: This work provides data for two specific nuclei with odd neutron numbers, Nd155 and Gd163, useful for constraining parameters in models that seek to answer the six proton shift in maximum deformation. Method: Data from the spontaneous fission of Cf252 were taken by the Gammasphere detector array at Lawrence Berkeley National Laboratory to observe the excited states of Nd155 and Gd163. Results: The structure of Gd163 has been expanded with the addition of two new levels and three new γ rays, which are found to be consistent with previously published calculations and the structure of Dy165. In Nd155, nine new levels and 12 new γ rays are observed. The spins and parities of the previously known levels in Nd155 have been reassigned from a ν3/2-[521] ground state configuration to a ν5/2+[642] isomeric configuration by comparison of these newly observed levels with levels in Nd153 and Sm155. Conclusion: Further experimentation is required to determine the energy of the newly reassigned ν5/2+[642] level in Nd155 with respect to the suspected ν3/2-[521] ground state. Additionally, more experiments should be conducted to further determine the structure of neutron rich nuclei, rarely produced in the spontaneous fission of Cf252, such as Gd163.