Nuclear structure dependence of fusion hindrance in heavy element synthesis
The production of the heaviest elements in fusion-evaporation reactions is substantially limited by very low cross sections, as fusion cross sections (including fusion-fission) are greatly reduced by the competing quasifission mechanism. Using the Australian National University Heavy Ion Accelerator Facility and CUBE detector array, fission fragments from the 48Ti + 204,208Pb and 50Ti + 206,208Pb reactions have been measured, with the aim to investigate how the competition between quasifission and fusion-fission evolves with small changes in entrance-channel properties associated mainly with the nuclear structure. Analysis of mass-distribution widths of strongly mass-angle-correlated fission fragments within the framework of the compound-nucleus fission theory demonstrates significant differences in quasifission (and therefore fusion) probabilities among the four reactions. The impact of nuclear structure on fusion highlights the importance of future radioactive beams. ; The authors acknowledge the support of Australian Research Council research grants DE140100784, DP140101337, DP160101254, DP170102318, DP170102423, German Academic Exchange Service (DAAD) via funds of the German Federal Ministry of Education and Research (BMBF). The Australian Federal Government NCRIS program is acknowledged for support of operations of the ANU Heavy Ion Accelerator Facility.
