  Three-body decay is a rare decay mode observed in a handful of unbound rare
isotopes. The angular and energy correlations between emitted nucleons are of
particular interest, as they provide invaluable information on the interplay
between structure and reaction aspects of the nuclear open quantum system. To
study the mechanism of two-nucleon emission, we developed a time-dependent
approach that allows us to probe emitted nucleons at long times and large
distances. We successfully benchmarked the new method against the Green's
function approach and applied it to low-energy two-proton and two-neutron
decays. In particular, we studied the interplay between initial-state
nucleon-nucleon correlations and final-state interaction. We demonstrated that
the time evolution of the two-nucleon wave function is strongly impacted by the
diproton/dineutron dynamics and that the correlations between emitted nucleons
provide invaluable information on the dinucleon structure in the initial-state.
