Search for elements 119 and 120

A search for production of the superheavy elements with atomic numbers 119 and 120 was performed in the Ti50+Bk249 and Ti50+Cf249 fusion-evaporation reactions, respectively, at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. Over four months of irradiation, the Bk249 target partially decayed into Cf249, which allowed for a simultaneous search for both elements. Neither was detected at cross-section sensitivity levels of 65 and 200 fb for the Ti50+Bk249 and Ti50+Cf249 reactions, respectively, at a midtarget beam energy of Elab=281.5 MeV. The nonobservation of elements 119 and 120 is discussed within the concept of fusion-evaporation reactions including various theoretical predictions on the fission-barrier heights of superheavy nuclei in the region of the island of stability.