Spatial orientation of the fission fragment intrinsic spins and their correlations

New experimental and theoretical results obtained in 2021 made it acutely clear that more than 80 years after the discovery of nuclear fission we do not understand the generation and dynamics of fission fragment (FF) intrinsic spins well, in particular their magnitudes, their spatial orientation, and their correlations. The magnitude and orientation of the primary FFs have a crucial role in defining the angular distribution and correlation between the emitted prompt neutrons, and subsequent emission of statistical (predominantly E1) and stretched E2 gamma rays, and their correlations with the final fission fragments. Here, we present detailed microscopic evaluations of the FF intrinsic spins, for both even- and odd-mass FFs, and of their spatial correlations. These point to a well-defined three-dimensional FF intrinsic spin dynamics, characteristics absent in semiphenomenological studies, due to the presence of the twisting spin modes, which artificially were suppressed in semiphenomenological studies.