Observation of superheavy nuclei produced in the reaction of Kr-86 with Pb-208

Following a prediction by Smolanczuk [Phys. Rev. C 59, 2634 (1999)], we sea rched for superheavy element formation in the bombardment of Pb-208 With 44 9-Mev Kr-86 ions. We have observed three decay chains, each consisting of a n implanted heavy atom and six subsequent alpha decays, correlated in time and position. In these decay chains, a rapid (ms) sequence of high energy a lpha particles (E-alpha greater than or equal to 10 MeV) indicates the deca y of a new high-Z element. The observed chains are consistent with the form ation of (293)118 and its decay by sequential alpha-particle emission to (2 89)116, (285)114, (281)112, (277)110, (273)Hs (Z = 108) and (269)Sg (Z = 10 6). The production cross section is 2.2(-0.8)(+2.6) pb.