Intruder configurations in Ne-29 at the transition into the island of inversion: Detailed structure study of Ne-28

Detailed ?-ray spectroscopy of the exotic neon isotope Ne-28 has been performed for the first time using the one-neutron removal reaction from( 29)Ne on a liquid hydrogen target at 240 MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne-28 and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Automated summary

In this study, detailed ?-ray spectroscopy of the Ne-28 isotope was performed for the first time using the one-neutron removal reaction from 29Ne. Based on an analysis of momentum distributions, a level scheme with spin-parity assignments was constructed for Ne-28 and the negative-parity states were identified for the first time. The results indicate a breakdown of the N = 20 and N = 28 shell gaps, presenting a challenge for theoretical description of the transition in the Ne isotopic chain.