Synthesizing any elements in the eighth period using either cold or hot fusion reactions remains a big challenge till date. Quasifission mechanism restricts complete fusion to an indeterminably low evaporation residue (ER) cross section for the superheavy nuclei. Entrance channel parameters of the heavy-ion reaction, fission barrier of compound nucleus, deformation parameters of the projectile and target nuclei, and the kinetic energy of the projectile are mostly responsible in governing the scales of the quasifission. Role of these factors has been examined explicitly by the experimental ER cross sections. Thorough comparisons lead us to infer that the entrance channel criteria contribute much lower extent than the deformation parameters do. The effect of deformation can be categorized into four rules as validated by all the reactions used except one $^{45}_{21}$Sc+$^{249}_{98}$Cf $\rightarrow ^{294}_{119}$Uue. Null result from this reaction is well explained by an improper choice of the projectile energy as shown theoretically by means of a statistical model approach, which is valid for a system having a large nucleon number so as to have intrinsically a high density of excited states. Optimal selection of the beam energy sets another rule. Therefore, these five rules can be treated as the rules of thumb for synthesizing the superheavy elements. Application of the first four rules can enable us to spot primarily a suitable reaction and finally exploitation of the fifth rule chooses the most appropriate reaction at a preferable excited energy to achieve the highest ER cross section for a superheavy element.
We have developed an empirical formula for survival probability for the superheavy nuclei by analyzing about 95 fusion experiments, which were classified into four categories based on the deformation parameters of a projectile-target system. Every category is analyzed in ten different entrance channel parameters; one of these displays the smoothest variation. That channel is none but the Z2/A, where Z and A are the atomic number and mass number, respectively. Further, the predicted empirical relation is improved by the inclusion of the fission barrier, separation energy, level density parameter, center of mass energy and fusion barrier height for the Z2/A term. Furthermore, the ER cross section is maximum at certain beam energy called the optimal energy. Thus finding the survival probability at the optimal energy is important to synthesizing a superheavy nucleus. We have developed an empirical formula for the survival probability at the optimal energy to facilitate future superheavy nuclei synthesis.
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