Generation, dynamics, and correlations of the fission fragments' angular momenta

The generation of angular momentum in fissioning nuclei has been a controversial topic. The predictions of different models disagree, particularly concerning the correlation between the fragments' angular momenta. In this letter, a time-dependent collective Hamiltonian model is constructed in the framework of the microscopic frozen Hartree-Fock approximation. The model presents a formalism to treat the generation of the angular momenta in the fission fragments due to the quantum uncertainty principle as well as the dynamics of the collective wave function during scission and the Coulomb reorientation phase. The model is able to describe a large part of the angular momentum found in experimental data. Some of the conclusions of the collective vibration model are supported by the quantum model but not all of the predictions are. Surprisingly, it is found that the angular momenta of the fragments are slightly correlated in a wriggling mode. In agreement with experimental data, the orientation of the angular momentum of each fragment is found to be mainly in the plane perpendicular to the fission axis. The magnitudes of the angular momenta are almost uncorrelated in agreement with the recent experimental data of Wilson et al., Nature (London) 590, 566 (2021). Additionally, the model shows that the octupole deformation significantly increases the angular momentum in the heavy fragment which was never expected in previous models.