Systematic Study of Quasifission in ⁴⁸Ca-induced reactions

Department of Nuclear Physics, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia.

^* e-mail: ben.swinton-bland@anu.edu.au
^** Present Address: National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA
^*** Present address: Department of Physics, Central University of Kerala, Kasaragod 671316, India
^**** Present address: Advanced Technology Institute, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom.

Published online: 6 April 2020

Abstract

The production of superheavy elements through the fusion of two heavy nuclei is severely hindered by the quasifission process, which results in the fission of heavy systems before an equilibrated compound nucleus (CN) can be formed. The heaviest elements have been synthesised using ⁴⁸Ca as the projectile nucleus. However, the use of ⁴⁸Ca in the formation of new superheavy elements has been exhausted, thus a detailed understanding of the properties that made ⁴⁸Ca so successful is required. Measurements of mass-angle distributions allow fission fragment mass distribution widths to be determined. The effect of the orientation of prolate deformed target nuclei is presented. Closed shells in the entrance channel are also shown to be more important than the stability of the formed CN in reducing the quasifission component, with reduced mass widths for reactions with the closed shell target nuclei ¹⁴⁴Sm and ²⁰⁸Pb. Comparison to mass widths for ⁴⁸Ti-induced reactions show a significant increase in the mass width compared to ⁴⁸Ca-induced reactions, highlighting the difficulty faced in forming new superheavy elements using projectiles with higher atomic number than ⁴⁸Ca.