Measurements of cross sections and decay properties of the isotopes of elements 112, 114, and 116 produced in the fusion reactions 233,238 U , 242Pu , and 248Cm + 48Ca

We have studied the dependence of the production cross sections of the isotopes ^282,283 112 and ^286,287 114 on the excitation energy of the compound nuclei ²⁸⁶112 and ²⁹⁰114 . The maximum cross section values of the xn -evaporation channels for the reaction ²³⁸U ( ⁴⁸Ca ,xn) ^286-x 112 were measured to be σ_3n = 2.5 ^+1.8 _-1.1 pb and σ_4n = 0.6 ^+1.6 _-0.5 pb ; for the reaction ²⁴²Pu ( ⁴⁸Ca ,xn) ^290-x 114 : σ_2n ∼0.5 pb , σ_3n = 3.6 ^+3.4 _-1.7 pb , and σ_4n = 4.5 ^+3.6 _-1.9 pb . In the reaction ²³³U ( ⁴⁸Ca ,2 4n) ^{277 279} 112 at E*=34.9±2.2 MeV we measured an upper cross section limit of σ_xn ⩽0.6 pb . The observed shift of the excitation energy associated with the maximum sum evaporation residue cross section σ_ER (E*) to values significantly higher than that associated with the calculated Coulomb barrier can be caused by the orientation of the deformed target nucleus in the entrance channel of the reaction. An increase of σ_ER in the reactions of actinide targets with ⁴⁸Ca is consistent with the expected increase of the survivability of the excited compound nucleus upon closer approach to the closed neutron shell N=184 . In the present work we detected 33 decay chains arising in the decay of the known nuclei ²⁸²112 , ²⁸³112 , ²⁸⁶114 , ²⁸⁷114 , and ²⁸⁸114 . In the decay of ²⁸⁷114 (α) → ²⁸³112 (α) → ²⁷⁹110 (SF) , in two cases out of 22, we observed decay chains of four and five sequential α transitions that end in spontaneous fission of ²⁷¹Sg ( T_α/SF = 2.4 ^+4.3 _-1.0 min) and ²⁶⁷Rf ( T_SF ∼2.3 h) , longer decay chains than reported previously. We observed the new nuclide ²⁹²116 ( T_α = 18 ⁺¹⁶ _-6 ms, E_α =10.66±0.07 MeV) in the irradiation of the ²⁴⁸Cm target at a higher energy than in previous experiments. The observed nuclear decay properties of the nuclides with Z=104 118 are compared with theoretical nuclear mass calculations and the systematic trends of spontaneous fission properties. As a whole, they give a consistent pattern of decay of the 18 even- Z neutron-rich nuclides with Z=104 118 and N=163 177 . The experiments were performed with the heavy-ion beam delivered by the U400 cyclotron of the FLNR (JINR, Dubna) employing the Dubna gas-filled recoil separator.