Optimum orientations of deformed nuclei for cold synthesis of superheavy elements and the role of higher multipole deformations

TLDR

The study extends fragmentation theory by incorporating a generalized nuclear proximity potential that accounts for deformations up to hexadecupole, and applies it to collisions involving deformed, oriented nuclei such as 208Pb and 48Ca and their neighbors. The analysis shows that optimal orientations are determined solely by quadrupole deformation signs, that hexadecupole deformations can enhance fusion depending on the reaction partners, and that for optimally oriented deformed nuclei the excitation energy minima are significantly lowered for cold elongated fusion while remaining unchanged for asymmetric hot fusion, leading to new favorable target–projectile combinations.

Abstract

For collisions between deformed and oriented nuclei, the fragmentation theory is extended for the generalized nuclear proximity potential, with deformations included up to the hexadecupole deformations. For co-planar nuclei, the orientations are shown to get optimized (uniquely fixed) by the signs of their quadrupole deformations alone, not affected by the signs of their hexadecupole deformations. The optimum orientations are obtained for both the 'hot compact', and 'cold elongated' configurations of any two colliding nuclei. The hexadecupole deformations are shown to help fusion (hot or cold), depending on the choice of the reaction partners. Calculations are made for the 208Pb- and 48Ca-induced reactions and the neighbouring deformed nuclei. The calculated fragmentation potentials for optimally oriented nuclei, compared with both nuclei taken spherical, show that the excitation energy of the potential energy minima is significantly lowered for cold (elongated) fusion of deformed nuclei, but it remains nearly the same for at least the asymmetric hot (compact) fusion reactions. A number of new minima (target–projectile combinations) arise due to the cold and nearly symmetric hot fusion of deformed, optimally oriented nuclei.