Using the total-Routhian-surface(TRS)method,the rotational behaviors of fission isomers in the second well of actinide nuclei234 242U,236 244Pu and238 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 andβ4≈0.03)fission isomers,theν12[981]neutron andπ12+[651]proton align simultaneously at rotational frequencyω≈0.4 0.6 MeV(corresponding to spin I≈80),which leads to clear upbending in moments of inertia(MoI’s).Our calculations have indicated that the hexadecapole deformationβ4influenced significantly the frequency of the rotational alignment of the proton12+[651]orbit.
From an inelastic excitation and breakup experiment with a12Be beam at 29 MeV/u,a large4He+8He cluster decay width of 1.1(2)MeV is determined for a state at an excitation energy of 10.3 MeV and with a spin parity of 0+.By using the R-matrix analysis,a cluster spectroscopic factor of 0.53(10)is extracted from the cluster partial width,providing a strong support for the clustering structure in12Be.A specially designed zero-degree telescope played an essential role in the present experiment and has been demonstrated to be a promising tool in future studies of the molecular-like resonances near the cluster separation threshold.
