Observation of Superheavy Nuclei Produced in the Reaction of 86Kr with 208Pb

Following a prediction by Smolan´czuk [Phys. Rev. C 59, 2634 (1999)], we searched for superheavy element formation in the bombardment of ²⁰⁸Pb with 449-MeV ⁸⁶Kr ions. We have observed three decay chains, each consisting of an implanted heavy atom and six subsequent α decays, correlated in time and position. In these decay chains, a rapid (ms) sequence of high energy α particles ( E_α>=10 MeV) indicates the decay of a new high- Z element. The observed chains are consistent with the formation of ²⁹³118 and its decay by sequential α-particle emission to ²⁸⁹116, ²⁸⁵114, ²⁸¹112, ²⁷⁷110, ²⁷³Hs ( Z = 108) and ²⁶⁹Sg ( Z = 106). The production cross section is 2.2^+2.6_-0.8 pb.