Synthesis of Superheavy Nuclei in the48Ca+244PuReaction

In bombardment of ${}^{244}\mathrm{Pu}$ with ${}^{48}\mathrm{Ca}$, we observed a decay sequence consisting of an implanted heavy atom, three subsequent $\alpha$ decays, and a spontaneous fission (SF), all correlated in time and position. The measured $\alpha$ energies and corresponding time intervals were $E_{\alpha }=9.71\mathrm{}$ MeV ( $\Delta t=30.4\mathrm{}$ s), 8.67 MeV ( $\Delta t=15.4\mathrm{}$ min), and 8.83 MeV ( $\Delta t=1.6\mathrm{}$ min); for the SF ( $\Delta t=16.5\mathrm{}$ min), the total deposited energy was approximately 190 MeV. The $\alpha$-particle energies together with the decay times and SF terminating the chain offer evidence of the decay of nuclei with high atomic numbers. This decay chain is a good candidate for originating from the $\alpha$ decay of the parent nucleus ${}^{289}114$, produced with a cross section of about 1 pb.