Collective rotations of fission isomers in actinide nuclei

Using the total-Routhian-surface (TRS) method, the rotational behaviors of fission isomers in the second well of actinide nuclei ^234–242U, ^236–244Pu and ^238–246Cm were investigated. The pairing-deformation-frequency self-consistent TRS calculations reproduced reasonably the experimental moments of inertia extracted from spectroscopic data. It is calculated that, in these largelyelongated (β₂ ≈ 0.65 and β₄ ≈ 0.03) fission isomers, the $$v\tfrac{1} {2}^ - [981]$$ neutron and $$\pi \tfrac{1} {2}^ + [651]$$ proton align simultaneously at rotational frequency ħω ≈ 0.4–0.6 MeV (corresponding to spin I ≈ 80ħ), which leads to clear upbending in moments of inertia (MoI's). Our calculations have indicated that the hexadecapole deformation β₄ influenced significantly the frequency of the rotational alignment of the proton $$\tfrac{1} {2}^ + [651]$$ orbit.