Radioactivity Signatures of Shell Closure: Insights from Quasifission Processes

The study aimed to examine quasifission experiments and perform a detailed analysis to correlate quasifission fragments with neutron and proton shell closures. The results show that the symmetry of the quasifission fragments depends on the energy of the projectile. Symmetric fragments were observed in fusion reactions leading to the formation of compound nuclei 216Ra and 220Ra, while other fusion reactions, resulting in actinide nuclei such as 227 Ac, 226Th, 250Cf, 256No, and 260No produced asymmetric quasifission fragments. These fragments, lying between 36 ≤ Zlightpeak ≤ 42 and 58 ≤ Zheavypeak ≤ 62, are signatures of proton sub-shell closure near Z = 40 and Z = 60. Corresponding neutron numbers were found to be 56 ≤ Nlightpeak ≤ 64 and 88 ≤ Nheavypeak ≤ 96. Additionally, during the synthesis of superheavy elements, light and heavy quasifission fragments were identified with proton numbers in the ranges 24 ≤ Zlightpeak ≤ 40 and 76 ≤ Zheavypeak ≤ 88, and 41 ≤ Nlightpeak ≤ 58 and 109 ≤ Nheavypeak ≤ 131. These findings provide strong evidence for proton shell closures at Z=40 and Z=60, as well as neutron shell closures at N=50 and N=120. The quasifission process therefore reveals significant insights into nuclear shell structures. Furthermore, the study highlights the critical role of reaction partner magicity and entrance channel parameters, including laboratory energy, in influencing the quasifission process.