Probing Dynamics of Fusion-Fission Process in Heavy to Very Heavy Nuclei

Indranil Mazumdar (Department of Nuclear & Atomic Physics, TIFR, Mumbai, India)

Studies in heavy-ion induced fusion-fission process has established itself as one of the major branches of low and medium energy nuclear structure and reaction physics. A plethora of dynamical processes manifest through the fusion-fission of two atomic nuclei over a wide range of projectile energy.  The process of fission followed by fusion of two heavy nuclei or survival of the Compound Nucleus (CN) against fission and formation of Evaporation Residues (ER) are deeply connected with various factors like, nuclear Shell Structure, Target-Projectile mass asymmetry, projectile energy, Angular Momentum distribution in the CN etc. Other than studying the dynamical effects associated with fusion and subsequent fission (or survival against fission) of heavy CN, there is also the long-standing desire to understand formation of very heavy or Super Heavy Elements (SHE).   

In this talk we plan to briefly review the present status of heavy-ion induced fusion-fission processes at energies above the Coulomb Barrier. We would like to touch upon aspects of fission followed by complete and incomplete fusion and processes like fast and quasi-fission. We will be primarily drawing from our measurements carried out at the Inter University Accelerator Centre, New Delhi using the Hybrid Recoil mass Analyser (HYRA) coupled with the TIFR 4π Sum-Spin spectrometer. We will provide a brief introduction to the subject of heavy-ion induced fusion followed by fission process and its wider ramifications in low and medium energy nuclear physics. We will summarise what we have learnt so far and what are the unresolved mysteries.  Example to support the current understanding of the subject will be primarily from our very recent measurements of angular momentum gated Evaporation Residues from the heavy ¹⁸⁶Pt and very heavy ²⁴⁰Cf nuclei. Detailed analysis using Statistical Model analysis and Dynamical approach will also be presented. We will also discuss the role of nuclear viscosity in the survival of the CN against fission.

Aspects of the Recoil of Mass Analyser and the 4π sum-spin spectrometer and possible future plans will also be touched upon.