Breaking of N=8 magicity in 13Be

TL;DR

This study investigates the breakdown of the N=8 magic number in 13Be using antisymmetrized molecular dynamics, revealing intruder states and cluster structures that challenge traditional shell model expectations.

Contribution

It demonstrates the disappearance of N=8 magicity in 13Be and proposes a detailed structure involving intruder states and cluster formations.

Findings

Unnatural parity 1/2^- state is lower than 5/2^+ state.

Low-lying 3/2^+ state with 2ħω configuration identified.

Cluster structures found in intruder states.

Abstract

Structure of $^{13}$Be was investigated with antisymmetrized molecular dynamics. The variation after spin and parity projections was performed. An unnatural parity $1/2^-$ state was suggested to be lower than $5/2^+$ state indicating that vanishing of the N=8 magic number occurs in $^{13}$Be. A low-lying $3/2^+$ state with a $2\hbar\omega$ configuration was also suggested. Developed cluster structures were found in the intruder states. Lowering mechanism of the intruder states was discussed in terms of molecular orbitals around a $2\alpha$ core.