The cold fusion reactions with lead and bismuth as targets were used in the synthesis of superheavy elements (SHE) with mass number up to 113. Researchers ignored the cold fusion reactions in the synthesis of SHE>113. This may be due to the improper choice of projectiles. The present study focusses on cold fusion reactions leading to the formation of SHE from Z = 112 to 126. Suitable projectiles for the fusion reaction using $^{208}$Pb and $^{209}$Bi targets were identified. The fusion and evaporation residue cross-sections are evaluated usingadvance statistical model. The produced cross-sections were compared with the available experiments. Suitable projectiles for synthesising the superheavy elementswith Z = 104–126 using lead and bismuth targets are predicted.The predicted production cross-sections vary from nanobarn (nb) to picobarn (pb). The use of spherical–spherical projectile and target yields larger cross-sections than spherical–deformed or deformed–spherical projectile andtarget combination.

The Coulomb fission may take place in a reaction if the maximum Coulomb excitation energy transfer exceeds the fission barrier of either the projectile or the target nucleus. This condition is satisfied in all the reactions used for the earlier blocking measurements of fission time-scale except for the reaction $^{208}$Pb + natural Ge crystal, where the time-scale is below the measurement limit of the blocking technique $\les$ 1 as. Inclusion of Coulomb fission in the data analysis of the blocking experiments leads us to interpret the measured time-scales longer than a few attoseconds (as) (about 1–2.2 as) due to slow Coulomb fission and those shorter than 1 as, as due to quasifission and fast Coulomb fission. Consequently, this finding resolves the critical discrepancies between the fission time-scales measured using the nuclear and blocking techniques. This, in turn, validates the fact that the quasifission and fast Coulomb fission time-scales are indeed of the order of zeptosecond (zs) in accordance with the nuclear experiment sand theories. The present results thus provide an essential input to the understanding of the fusion evaporation reaction during the formation of heavy elements.