ROLE OF NON-AXIAL SHAPES IN THE SADDLE-POINT ENERGY OF HEAVIEST NUCLEI

The role of non-axial shapes in the saddle-point energy of heaviest nuclei is studied in a multidimensional deformation space. The main attention is given to the effect of the high-multipolarity, lambda = 6, non-axial deformations, which is studied for the first time. The analysis is performed within a macroscopic-microscopic approach. Generally, a 10-dimensional deformation space is used in the analysis, but some tests are done in even 13 dimensions. A large number of about 300 even-even heavy and superheavy nuclei with proton number 98 <= Z <= 126 and neutron number 134 <= N <= 192 is considered. It is found that the inclusion of the non-axial shapes of the multipolarity lambda = 6 lowers the saddle-point energy relatively little, by up to about 0.4 MeV. Together with earlier results on the effect of the quadrupole (lambda = 2) and hexadecapole (lambda = 4) shapes, this indicates for the convergence of the effect to zero, with increasing lambda. As the ground-state shapes of the considered nuclei are axially symmetric, the discussion also concerns the height of the fission barrier. The heights of our barriers are compared with experimental ones and also with those of other authors.