Thermal Fission Barriers for 232Th in Two Dimensions

Jordan McDonnell, University of Tennessee, Knoxville

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Theoretical fission barrier results are presented for the light actinide thorium-232 at several excitation energies. Using the self-consistent constrained Skyrme-Hartree-Fock theory with BCS pairing, we obtain potential energy surfaces in terms of quadrupole elongation paired with two other collective degrees of freedom. Near the first saddle, triaxial configurations were found to be significant. At larger quadrupole deformations, axial symmetry is found to be restored and reflection asymmetry becomes significant. Beyond the second saddle, a very shallow third minimum is found, representing a hyperdeformed reflection asymmetric fission isomer reported in the literature. We find that increasing excitation energy has the effect of increasing the symmetry of the nucleus along its path to fission. The third minimum also dissolves as excitation energy is raised to the critical temperature where pairing correlations disappear. This calculation for thorium-232 serves as a benchmark for an upcoming survey of actinide fission barriers and fission observables, as well as an evaluation of the performance of next-generation nuclear energy density functionals.

Abstract Author(s): J.D. McDonnell, W. Nazarewicz, N. Schunck, J.A. Sheikh