Reduced quasifission competition in fusion reactions forming neutron-rich heavy elements

Measurements of mass-angle distributions (MADs) for Cr + W reactions, providing a wide range in the neutron-to-proton ratio of the compound system, (N/Z)CN, have allowed for the dependence of quasifission on the (N/Z)CN to be determined in a model-independent way. Previous experimental and theoretical studies had produced conflicting conclusions. The experimental MADs reveal an increase in contact time and mass evolution of the quasifission fragments with increasing (N/Z)CN, which is indicative of an increase in the fusion probability. The experimental results are in agreement with microscopic time-dependent Hartree-Fock calculations of the quasifission process. The experimental and theoretical results favor the use of the most neutron-rich projectiles and targets for the production of heavy and superheavy nuclei.This work is supported by the National Science Foundation under Grants No. PHY-1102511 and No. IIA-1341088, by the U.S. Department of Energy under Grant No. DE-FG02- 96ER40975 with Vanderbilt University, and the Australian Research Council Grants No. DP110102858, No. DP140101337, No. FL110100098, No. DP130101569, No. FT120100760, and No. DE140100784. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award No. DE-NA0000979. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility