Search for superheavy elements using the ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$${+}^{254}$${\mathrm{Es}}^{\mathrm{g}}$ reaction

We measured upper limits for the production of superheavy elements from the compound nucleus reaction ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$${+}^{254}$Es. This combination permits the closest approach to the predicted island of stability at the 184 closed-neutron shell of any practical fusion reaction. We used aqueous and gas-phase separations to isolate superheavy element fractions within an hour from the end of the bombardments. In these experiments we did not observe superheavy elements above a limit of 3×${10}^{\mathrm{-}31}$ ${\mathrm{cm}}^2$ for spontaneous-fission half-lives from fractions of a day to a few months.