Microscopic Description of Rotational Nuclear Fission Elucidates Fragment Spin Generation and Scission Mechanism

TL;DR

This paper uses microscopic time-dependent density functional theory to analyze how rotating compound nuclei like 240Pu undergo fission, revealing details about fragment spins, scission modes, and neck configurations at various excitation energies.

Contribution

It provides new microscopic insights into the scission mechanism and fragment spin generation in rotating fissioning nuclei, highlighting the impact of excitation energy.

Findings

Fragment spin ratios are stable at high spins but decrease with increasing excitation energy.

Bending scission mode dominates at low excitation energies.

Thicker, elongated necks and perpendicular nucleon emission are observed during rapid rotations.

Abstract

The generation of fission fragment spin as a probe of scission mechanism remains a question of considerable interests. We present here microscopic calculations of rapidly rotating fission of the compound nucleus 240Pu under varying initial conditions within the time-dependent density functional theory framework. The obtained spin ratio of light to heavy nascent fragments is unchanged up to high spins but diminished as excitation energies increase, indicating sawtooth structures in fragment spins would fade away at high excitations rather than high angular momentum. Further analysis elucidates that the bending scission mode is predominated at low excitation energies, which has been under intense debates. Results also show thicker and elongated neck configurations, along with scission nucleons emitted perpendicular to the fission axis, owing to rapid rotations. These findings offer insights into the scission mechanism of rotating compound nuclei that have usually been overlooked in earlier studies.