Lifetime and fragment correlations for the two-neutron decay of $^{26}$O ground state

TL;DR

This study models the decay of $^{26}$O using a three-body approach, revealing strong effects of configuration mixing on decay width and providing lifetime estimates consistent with recent experiments.

Contribution

It introduces a detailed three-body model for $^{26}$O decay, highlighting the impact of configuration mixing and core recoil on decay properties, which was not thoroughly explored before.

Findings

Strong configuration mixing significantly affects decay width.

Narrow lifetime vs. decay energy boundaries established.

Decay energy of $^{26}$O is constrained to less than ~1 keV.

Abstract

The structure and decay of $^{26}$O are investigated in a three-body $^{24}$O+$n+n$ model suitable for studies of the long-lived (including radioactivity timescale) states. We have found extremely strong effect of the subbarrier configuration mixing on the decay width of true $2n$ emitters due to core recoil and neutron-neutron final state interaction. This effect is far exceeding analogous effect in the true $2p$ emitters. Our calculations provide reasonably narrow boundaries for the lifetime vs.\ decay energy dependence for the true $2n$ emission. An upper limit of $\sim 1$ keV for the decay energy of the unbound $^{26}$O is inferred based on the recent experimental lifetime value.