Border of the Island of Inversion: Unbound states in $^{29}$Ne

Abstract

The nucleus 29 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 Ne firmly inside the island of inversion, has yet been observed. Here, the first investigation of unbound states of 29 Ne is reported. The states were populated in 30 Ne(p, pn) and 30 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 -assignments for the observed states. The lowest-lying resonance at an excitation energy of 1.48(4) MeV shows clear signs of a significant =3-component, giving first evidence for f 7/2 single particle strength in 29 Ne. The excitation energies and strengths of the observed states are compared to shell-model calculations using the sdpf-u-mix interaction.