Synthesis of Superheavy Nuclei in the Reactions of 244PU and 248CM with 48CA

This paper presents results of the experiments aimed at producing long-lived superheavy elements located near the spherical shell closures with Z ≥ 114 and N ≥ 172. For the synthesis of superheavy nuclei, we used a combination of neutron-rich reaction partners, with ²⁴⁴Pu and ²⁴⁸Cm targets and a ⁴⁸Ca projectile. The sensitivity of the present experiment exceeded by more than two orders of magnitude previous attempts to synthesize superheavy nuclides in reactions of ⁴⁸Ca projectiles with actinide targets. The large measured α-particle energies of the newly observed nuclei, together with the long decay times and spontaneous fission terminating the chains, offer evidence of the decay of nuclei with high atomic numbers. The decay properties of the synthesized nuclei are consistent with the consecutive α-decays originating from the parent nuclides ^288,289114 and ²⁹²116 produced in the 3n and 4n-evaporation channels with cross sections of half of a picobarn. The present observations can be considered as experimental evidence of the existence of the "island of stability" of superheavy elements.