Static fission properties of actinide nuclei

TL;DR

This paper calculates fission barrier heights and superdeformed minima energies for 75 actinide nuclei using advanced microscopic-macroscopic models, achieving close agreement with experimental data and discussing discrepancies and anomalies.

Contribution

It applies state-of-the-art deformation minimization and saddle point methods within the Woods-Saxon model to improve understanding of actinide fission properties.

Findings

RMS deviation of 0.82-0.94 MeV for barriers

RMS error of 0.53 MeV for superdeformed minima

Discrepancies linked to pairing and data interpretation issues

Abstract

Fission barriers heights and excitation energies of superdeformed isomeric minima are calculated within the microscopic - macroscopic Woods - Saxon model for 75 actinide nuclei for which the experimental data are known. State - of - the - art methods were used: minimization over many deformation parameters for minima and the imaginary water flow on many - deformation energy grid for saddles, including nonaxial and reflection-asymmetric shapes. We obtain 0.82 - 0.94 MeV rms deviation between the calculated and experimental barriers and 0.53 MeV rms error in the excitation of superdeformed minima (SD). Experimental vs theory discrepancies seem to be of various nature and not easy to eliminate, especially if one cares for more than one or two observables. As an example, we show that by strengthening pairing in odd systems one can partially improve agreement in barriers, while spoiling it for masses. We also discuss the "thorium anomaly" and suggest its possible relation to a different way in which the Ac and Th barriers are derived from experimental data.