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 Dy-66 isotopic chain to the Nd-60 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, Nd-155 and Gd-163, useful for constraining parameters in models that seek to answer the six proton shift in maximum deformation. Method: Data from the spontaneous fission of Cf-252 were taken by the Gammasphere detector array at Lawrence Berkeley National Laboratory to observe the excited states of Nd-155 and Gd-163. Results: The structure of Gd-163 has been expanded with the addition of two new levels and three new gamma rays, which are found to be consistent with previously published calculations and the structure of Dy-165. In Nd-155, nine new levels and 12 new gamma rays are observed. The spins and parities of the previously known levels in Nd-155 have been reassigned from a nu 3/2(-)[521] ground state configuration to a nu 5/2(+)[642] isomeric configuration by comparison of these newly observed levels with levels in Nd-153 and Sm-155. Conclusion: Further experimentation is required to determine the energy of the newly reassigned nu 5/2(+)[642] level in Nd-155 with respect to the suspected nu 3/2-[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 Cf-252, such as Gd-163.