Direct observation of an isomeric state in ⁹⁸Rb and nuclear properties of exotic rubidium isotopes measured by laser spectroscopy

Fast-beam collinear laser spectroscopy experiments on rubidium have been performed at the ISAC radioactive ion beam facility at TRIUMF. Most recently, the neutron-rich ⁹⁸Rb isotope has been studied for the investigation of shape coexistence. Two long-lived nuclear states in ⁹⁸Rb have been clearly observed for the first time: a low-spin state, assigned a spin of I = 0, and a high-spin state. The high-spin state is tentatively assigned a spin of I = 3 based on this analysis in combination with gamma decay results. The measured nuclear properties of the two states are presented, alongside unpublished values of the neutron-deficient isotopes investigated previously. The mean-square charge radii of both states in ⁹⁸Rb are observed to continue along the isodeformation line present after the N = 60 onset of deformation.