Evolution of shell gaps in the neutron-poor calcium region via invariant-mass spectroscopy beyond the proton dripline

At the National Superconducting Cyclotron Laboratory, a secondary beam of ³⁷Ca was impinged on a ⁹Be target resulting in a set of reactions populating nuclei beyond the proton dripline of the neutron-poor calcium region. Invariant-mass spectroscopy of prompt proton decay was used to determine the ground-state masses and low-lying structure of ³⁴K, ³⁷Sc, and ³⁸Sc. These masses provide new insights into the isotopic and isotonic trends in the Wigner-removed separation energies, which help elucidate evolving shell structure, showing a fading of the Z=20 shell gap for N≤18 and indications of a N=16 subshell gap.