Isospin symmetry investigation of the proton-unbound nucleus T = 3/2 55Cu

Abstract

This study reports the status of the first in-beam γ-ray spectroscopic study of excited states in the exotic neutron-deficient $T_z=$-3/2 nucleus ⁵⁵Cu. The nucleus was produced via knock-out reactions at the Radioactive Isotope Beam Factory, located at the RIKEN-Nishina Center. Several γ-ray transitions were detected using the DALI2⁺ γ-ray detector array. The comparison with isobaric analogue states in the mirror nucleus ⁵⁵Fe will provide valuable insights into isospin-non-conserving effects beyond nuclear stability. The proton occupation of the 1$p_{3/2}$ orbital is expected to play a significant effect on the orbital's charge radius due to the isovector monopole polarizability, which can be linked to the measured mirror energy differences.