Nuclear Scission and Quantum Localization

We examine nuclear scission within a fully quantum-mechanical microscopic framework, focusing on the nonlocal aspects of the theory. Using ${}^{240}\mathrm{Pu}$ hot fission as an example, we discuss the identification of the fragments and the calculation of their kinetic, excitation, and interaction energies, through the localization of the orbital wave functions. We show that the disentanglement of the fragment wave functions is essential to the quantum-mechanical definition of scission and the calculation of physical observables. Finally, we discuss the fragments’ prescission excitation mechanisms and give a nonadiabatic description of their evolution beyond scission.

Figure 1

Interaction energies plotted as a function of neck size ($Q_N$). The solid black and red dashed curves are the nuclear interaction energies before and after localization, respectively, (energy scale on the left $y$ axis), and the dotted green curve is the exchange part of the 2-body component of the interaction energy (energy scale on the right $y$ axis). The inset shows the effect of the localization on the densities of the fragments at scission.

Figure 2

Individual quasiparticle states before (top panel) and after (bottom panel) localization at scission. Proton states are shown as red crosses and neutron states as black disks. The $x$ axis gives the occupation ($v_i^2$) of the state, while the $y$ axis gives its localization (${\ell }_i$).