Unexpected isotopic trends in synthesis of superheavy nuclei

The production cross section for the heaviest nuclei in the Ca-48 induced hot fusion-evaporation reactions is shown to depend on the isotopic composition of actinide target. It is analyzed within the dinuclear system model for compound nucleus formation. In the actinide-based reactions most neutron-rich targets available for the experiment lead to smaller cross sections. New optimal reactions for the synthesis of superheavy nuclei are suggested.