All collective potentials shown in Fig. 4 have two-humped shapes and similar widths. Only in the case of Rf, can one see an additional small third external barrier. The outer barrier is systematically reduced with . The differences between open and solid symbols illustrate the effect of triaxiality on the inner barriers. The strongest effect is predicted for the nucleus , where the barrier is lowered by more than 3MeV due to triaxiality. However, for lighter isotones with , the role of triaxiality is modest.
For completeness, it is interesting to look at the neutron and proton spectral pairing gaps calculated along the static fission paths shown in Fig. 4. They are shown in Fig. 5. As already mentioned, the ground-state neutron pairing gaps are equal to 0 in all the =184 isotones, whereas the proton gaps change from 1.3MeV in Rf) to less than 0.5MeV in . In the sub-barrier regions of the fission paths (shadowed regions in the plot), neutron and proton spectral pairing gaps fluctuate around 1MeV.
The size of a fission barrier is a measure of stability of the nucleus against spontaneous fission. The static fission barriers shown in Fig. 4 suggest a possible increase of the stability against spontaneous fission for . This predicted increase of the stability supports the results obtained in our previous paper, where the same nuclei were considered within the SHF+BCS(G) framework, but with the pairing strengths of Eq. (1) scaled to reproduce the pairing gaps of the finite-range droplet model (FRDM).