The synthesis of an isotope of the new element 114 with mass number 287

The reaction 48Ca + 242Pu was investigated with the aim to synthesize a new isotope of the heaviest element Z = 114. The experiment was performed at a beam energy resulting in an excitation energy of the compound nucleus of 33.5 MeV. For the collected beam dose of 7.5 · 1018, we observed two decay chains both consisting of an implanted heavy nucleus, a subsequent α-decay and a spontaneous fission (SF). For the first sequence the measured α-particle energy and the corresponding time interval were: Eα = 10.29 ± 0.02 MeV and Δt = 1.32 s; for the spontaneous fission Δt =559.6 s. For the second sequence a signal was registered from an α-particle, which had escaped the detector, ΔEα = 2.31 MeV, Δt = 14.45 s; for the spontaneous fission Δt = 228.6 s. The decay chains originated from the α-decay of the new isotope Z = 114 with mass number 287 were terminated by the SF of the previously investigated isotope 283112. The new nuclide 287114 was produced in the fusion reaction in the 3n-evaporation channel with a cross section of about 2.5 pb. The observed radioactive properties of the synthesized nuclei 287114 together with the data obtained earlier for the isotope 289114 and the products of its α-decay, viz the isotopes 283,285112, are considered as a direct proof of the existence of the 'island of stability' of superheavy elements predicted more than 30 years ago