Two-Neutron Sequential Decay of $^{24}$O

TL;DR

This study observed a two-neutron unbound excited state in $^{24}$O, providing evidence for sequential decay through an intermediate $^{23}$O state, challenging simpler decay models.

Contribution

First experimental evidence of sequential two-neutron decay in $^{24}$O via an intermediate $^{23}$O state.

Findings

Identified a state at 715 keV above the two-neutron separation energy.

Observed decay correlations consistent with sequential decay.

Di-neutron and phase-space models failed to explain the correlations.

Abstract

A two-neutron unbound excited state of $^{24}$O was populated through a (d,d') reaction at 83.4 MeV/nucleon. A state at $E = 715 \pm 110$ (stat) $\pm 45 $ (sys) keV with a width of $\Gamma < 2$ MeV was observed above the two-neutron separation energy placing it at 7.65 $\pm$ 0.2 MeV with respect to the ground state. Three-body correlations for the decay of $^{24}$O $\rightarrow$ $^{22}$O + $2n$ show clear evidence for a sequential decay through an intermediate state in $^{23}$O. Neither a di-neutron nor phase-space model for the three-body breakup were able to describe these correlations.