Gamma-Ray Angular Distribution and Linear Polarization Measurements in ²⁵Ne

The conventional magic number N=20 has been shown to break down in the region of neutron-rich nuclei centered around ³²Mg (Z=12, N=20) known as the N=20 Island of Inversion. At the same time, a new magic number at N=16 has been suggested to emerge around ²⁴O (Z=8, N=16). The neutron-rich nucleus ²⁵Ne (Z=10, N=15) lies in this zone of rapid change in nuclear structure. Consequently, its detailed spectroscopy can provide important benchmarks to probe the underlying mechanisms of shell evolution. The ongoing analysis of an ¹⁸O beam on ⁹Be target fusion evaporation experiment using the state-of-the-art Gamma Ray Energy Tracking In-beam Nuclear Array (GRETINA) and the Fragment Mass Analyzer (FMA) at Argonne National Laboratory (ANL) will be presented. In this work, states in ²⁵Ne at high excitation energy were populated following the evaporation of two protons. By exploiting the significant degree of alignment in fusion evaporation, gamma-ray angular distribution and linear polarization analyses were performed to obtain information on the multipolarities of the observed transitions, clarifying the ²⁵Ne level scheme. This work represents the first use of GRETINA as a Compton polarimeter in a fusion-evaporation experiment. The experimental results were compared with shell model calculations using the FSU multishell effective interaction, showing good agreement.