Main restrictions in the synthesis of new superheavy elements: Quasifission and/or fusion fission

The synthesis of superheavy elements stimulates the effort to study the peculiarities of the complete fusion with massive nuclei and to improve theoretical models in order to extract knowledge about reaction mechanism in heavy-ion collisions at low energies. We compare the theoretical results of the compound nucleus (CN) formation and evaporation residue (ER) cross sections obtained for the 48Ca + 248Cm and 58Fe + 232Th reactions leading to formation of CN with A = 296 and A = 290 of the superheavy element Lv (Z = 116), respectively. The ER cross sections, which can be measured directly, are determined by the complete fusion and survival probabilities of the heated and rotating CN. Those probabilities cannot be measured unambiguously but the knowledge about them is important to study the formation mechanism of the observed products and to estimate the ER cross sections of the expected isotopes of elements. To this aim, the 48Ca + 249Cf and 64Ni + 232Th reactions are considered too. The use of the mass values of superheavy nuclei calculated in the framework of the macroscopic-microscopic model by the Warsaw group leads to smaller ER cross section for all of the reactions in comparison with the case of using the masses calculated by P. M¨oller et al..