Analysis of the unbound spectrum of $^{12}$Li

TL;DR

This paper investigates the unbound nucleus $^{12}$Li using a multistep shell model approach in the complex energy plane, revealing an antibound ground state and several low-energy narrow states from resonance coupling.

Contribution

It introduces a complex-energy multistep shell model analysis for $^{12}$Li, highlighting the antibound ground state and low-energy resonances, advancing understanding of unbound nuclei.

Findings

Ground state is an antibound $2^-$ state.

Identifies narrow low-energy states from resonance coupling.

Highlights the role of continuum states near threshold.

Abstract

The unbound nucleus $^{12}$Li is evaluated by studying three-neutron one-proton excitations within the multistep shell model in the complex energy plane. It is found that the ground state of this system consists of an antibound $2^-$ state. A number of narrow states at low energy are found which ensue from the coupling of resonances in $^{11}$Li to continuum states close to threshold.