Observation of Superheavy Nuclei Produced in the Reaction of K 86 r with P 208 b

Following a prediction by Smola\\ifmmode \\acute{n}\\else \\'{n}\\fi{}czuk [Phys. Rev. C 59, 2634 (1999)], we searched for superheavy element formation in the bombardment of ${}^{208}\\mathrm{Pb}$ with 449-MeV ${}^{86}\\mathrm{Kr}$ ions. We have observed three decay chains, each consisting of an implanted heavy atom and six subsequent $\\ensuremath{\\alpha}$ decays, correlated in time and position. In these decay chains, a rapid (ms) sequence of high energy $\\ensuremath{\\alpha}$ particles ( ${E}_{\\ensuremath{\\alpha}}\\ensuremath{\\ge}10\\mathrm{MeV}$) indicates the decay of a new high- $Z$ element. The observed chains are consistent with the formation of $^{293}118$ and its decay by sequential $\\ensuremath{\\alpha}$-particle emission to $^{289}116$, $^{285}114$, $^{281}112$, $^{277}110$, ${}^{273}\\mathrm{Hs}$ ( $Z\\phantom{\\rule{0ex}{0ex}}=\\phantom{\\rule{0ex}{0ex}}108$) and ${}^{269}\\mathrm{Sg}$ ( $Z\\phantom{\\rule{0ex}{0ex}}=\\phantom{\\rule{0ex}{0ex}}106$). The production cross section is ${2.2}_{\\ensuremath{-}0.8}^{+2.6}\\mathrm{pb}$.