The nucleus ${}^{29}\mathrm{Ne}$ is situated at the border of the island of inversion. Despite significant efforts, no bound low-lying intruder $f_{7/2}$ state, which would place ${}^{29}\mathrm{Ne}$ firmly inside the island of inversion, has yet been observed. Here, the first investigation of unbound states of ${}^{29}\mathrm{Ne}$ is reported. The states were populated in ${}^{30}\mathrm{Ne}(p,pn)$ and ${}^{30}\mathrm{Na}(p,2p)$ reactions at a beam energy of around 230 MeV/nucleon, and analyzed in terms of their resonance properties, partial cross sections, and momentum distributions. The momentum distributions are compared to calculations using the eikonal, direct reaction model, allowing $\ell$ assignments for the observed states. The lowest-lying resonance at an excitation energy of 1.48(4) MeV shows clear signs of a significant $\ell =3$ component, giving first evidence for $f_{7/2}$ single particle strength in ${}^{29}\mathrm{Ne}$. The excitation energies and strengths of the observed states are compared to shell-model calculations using the sdpf-u-mix interaction.

• Received 3 December 2021
• Accepted 1 February 2022

DOI:https://doi.org/10.1103/PhysRevC.105.034301

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Published by the American Physical Society