In the bombardment of a ${}^{244}\mathrm{Pu}$ target with ${}^{48}\mathrm{Ca}$ ions, we observed two identical decay sequences of genetically linked events, each consisting of an implanted heavy atom, two subsequent α decays, and terminated by a spontaneous fission. The measured α energies and corresponding half-lives of the sequential chain members were $E_{\alpha }=9.84\mathrm{}\pm 0.05\hspace{0.5em}\mathrm{MeV}$ ${(T}_{1/2}{=1.9\mathrm{}}_{-0.8}^{+3.3\mathrm{}}\hspace{0.5em}\mathrm{s})$ and $9.17\pm 0.05\hspace{0.5em}\mathrm{MeV}$ ${(T}_{1/2}{=9.8\mathrm{}}_{-3.8}^{+18\mathrm{}}\hspace{0.5em}\mathrm{s});$ for the spontaneous fission ${(T}_{1/2}{=7.5\mathrm{}}_{-2.9}^{+14\mathrm{}}\hspace{0.5em}\mathrm{s}),$ the total energies deposited in the detector array were $213\pm 2$ and $221\pm 2\hspace{0.5em}\mathrm{MeV}.$ The decay properties of the synthesized nuclei are consistent with the consecutive α decays originating from the parent even-even nucleus ${}^{288}114,$ produced in the $4n$-evaporation channel with a cross section of about 1 pb. ${}^{288}114$ and ${}^{284}112$ are the heaviest known α-decaying even-even nuclides, following the production of ${}^{260}\mathrm{Sg}$ and ${}^{266}\mathrm{Sg}$ $\mathrm{}(Z=106\mathrm{})\mathrm{}$ and the observation of α decay of ${}^{264}\mathrm{Hs}$ $\mathrm{}(Z=108\mathrm{}).$ The observed radioactive properties of ${}^{288}114$ and the daughter nuclides match the decay scenario predicted by the macroscopic-microscopic theory.

• Received 1 February 2000

DOI:https://doi.org/10.1103/PhysRevC.62.041604