Approaches to Determining the Nuclear Neck Radius at the Point of Scission

A comparative analysis of methods for determining the nuclear neck radius r_n at the point of scission during the fission of actinide nuclei is presented. Classical approaches based on the liquid drop model, modern methods employing time-dependent density functional theory, and the Born–Oppenheimer approximation (BOA) are examined. An original approach is proposed, which is based in the concept of “cold” fission, with an emphasis on analyzing the spin distributions of fission fragments. A quantitative correlation is found between the neck radius and fragment spins through transverse bending- and wriggling oscillations. For the nuclei 233Th, 238U, and 252Cf, the estimated neck radius ranges from 1.5 to 2.2 fm, showing consistency with various theoretical approaches and confirming their applicability.