Eleven new heaviest isotopes of elements Z=105 to Z=117 identified among the products of Bk-249+Ca-48 reactions

The heaviest isotopes of elements Z = 117 to Z = 105, (294)117, (293)117, (290)115, (289)115, (286)113, (285)113, (282)Rg, (281)Rg, (278)Mt, (274)Bh, and (270)Db, were identified by means of the Dubna gas-filled recoil separator among the products of the Bk-249 + Ca-48 reaction. The details of the observed six decay chains, indicating the production and decay of isotopes (293)117 and (294)117, are presented and discussed. The decay energies and resulting half-lives of these new nuclei show a strong rise of stability with increasing neutron number, validating the concept of the island of enhanced stability for superheavy nuclei [Oganessian et al., Phys. Rev. Lett. 104, 142502 (2010)].