Scission configurations and their implication in fission-fragment angular momenta

Abstract

The generation of sizable angular momenta in fragments formed in low-energy nuclear fission is described microscopically within the general quantum-mechanical framework of orientation pumping due to the Heisenberg uncertainty principle. Within this framework, we make use of the results of Skyrme-Hartree-Fock plus BCSpairing calculations of fragment deformabilities to deduce a distribution of fission-fragment spins as a function of the fragment total excitation energy.We consider a fragmentation corresponding to a pair of deformed fragments and for which fission data are available. The properties of the scission configurations determine to a large extent the fission-fragment spins. This is why we pay particular attention to quantitatively defining the scission configurations and to studying the various implications of such a specific choice. A fair qualitative agreement with data is demonstrated and discussed within the limits of the simple scission-configuration model used here

Description of induced nuclear fission with Skyrme energy functionals: Static potential energy surfaces and fission fragment properties

“…While these degrees of freedom are most likely sufficient to cover the physics of spontaneous fission, where a detailed knowledge of scission is not really necessary, we point out that the potential energy surface becomes increasingly complex near scission: further studies of induced fission will most likely require choosing better sets of collective variables, for example quantities related to each fragment [25,85].…”

“…It was recognized early on that the competition between the repulsive Coulomb and the attractive nuclear force may induce the scission of the nucleus even when there still remains a sizable neck between the two nascent fragments: the ratio of the Coulomb energy over the nuclear interaction energy can, therefore, provide a complementary, dynamical, criterion for scission [84,85]. Recently, a similar approach was formalized in the context of nuclear density functional theory [37].…”

Isomeric ratio measurements with the ILL LOHENGRIN spectrometer

“…This also questions on the mechanism of angular momentum generation [6,[14][15][16][17] which is the weakness of the nuclear data evaluation.…”

Phenomenological models of the energy dependence in fission

“…In addition, the "orientation pumping" mechanism [15], due to the uncertainty principle, is used in the model to account for the angular momentum of the fragments.…”