Pauli-principle driven correlations in four-neutron nuclear decays.

Mechanism of simultaneous non-sequential four-neutron ($4n$) emission (or `true' $4n$-decay) has been considered in phenomenological five-body approach. This approach is analogous to the model of the direct decay to the continuum broadly applied to $2n$- and $2p$-decays. It is demonstrated that $4n$-decay fragments should have specific energy and angular correlations reflecting strong spacial correlations of `valence' neutrons orbiting in their $4n$-precursors. Due to the Pauli exclusion principle, the valent neutrons are pushed to the symmetry-allowed configurations in the $4n$-precursor structure, which causes a `Pauli focusing' effect. Prospects of the observation of the Pauli focusing have been considered for the $4n$-precursors $^7$H and $^{28}$O. Fingerprints of their nuclear structure or/and decay dynamics are predicted.