Effects of Rotation, Blocking and Octupole Deformation on Pairing Correlations in the U and Pu Isotopes

By including octupole correlations in the Nilsson potential, the ground-state rotational bands in the reflection-asymmetric (RA) nuclei are investigated by using the cranked shell model (CSM) with the monopole and quadrupole pairing correlations treated by a particle-number-conserving (PNC) method. The experimental kinematic moments of inertia (MoIs) for alternating-parity bands in the even-even nuclei ^236, \, 238 \rmU and ^238, \, 240 \rmPu, as well as parity-doublet bands in the odd- A nuclei ^237 \rmU and ^239 \rmPu are reproduced well by the PNC-CSM calculations. The higher J^(1) for the intrinsic s = -i bands in ^237 \rmU and ^239 \rmPu, compared with the s = +1 bands in the neighboring even-even nuclei ^236, \, 238 \rmU and ^238, \, 240 \rmPu, can be attributed to the pairing gap reduction due to the Pauli blocking effect. The gradual increase of J^(1) versus rotational frequency can be explained by the pairing gap reduction due to the rotation. The MoIs of reflection-asymmetric nuclei are higher than those of reflection-symmetric (RS) nuclei at low rotational frequency. Moreover, the inclusion of a larger octupole deformation \varepsilon_3^ in the RA nuclei results in more significant pairing gap reduction compared with the RS nuclei.