Upper Limit for the 248Cm(50Ti, xn)298−xOg Reaction Cross Section

Abstract

After the synthesis of element 113, nihonium (Nh) via the 209Bi(70Zn,n)278Nh cold fusion reaction using the RIKEN heavy-ion Linear ACcelerator (RILAC) and the GAs-filled Recoil Ion Separator (GARIS), the search for the heaviest isotopes of oganesson was initiated with GARIS-II by means of the 248Cm(50Ti,xn)298−xOg fusion evaporation reaction. The optimal bombarding energy for the 50Ti + 248Cm reaction was determined from the quasielastic barrier distribution extracted from the excitation function of quasielastic backscattering. This method optimizes the compound nucleus formation. The search for Og was conducted for 39 days on the basis of the experimentally derived 50Ti beam energy of 227.9(5) MeV at the middle of 248Cm target. A precise analysis of the dataset based on multiple event search strategies revealed no decay chains with a total dose on 248Cm target of 4.93 × 1018 50Ti projectiles, reaching a sensitivity of 0.27 pb and a 1σ upper cross section limit of 0.50 pb.