Single-particle structure along the boundary of the “island of inversion”: Radioactive beam spectroscopy of ${}^{33}\mathrm{Si}$ and ${}^{34}\mathrm{P}$

Intermediate-energy Coulomb excitation has been used to study excited states in the radioactive $N=19\mathrm{}$ nuclei ${}^{33}\mathrm{Si}$ and ${}^{34}\mathrm{P},$ which are neutron-rich spherical nuclei located along the boundary of the “island of inversion.” The present results for the 1010 keV state in ${}^{33}\mathrm{Si}$ and states up to 2.2 MeV excitation energy in ${}^{34}\mathrm{P}$ can be understood in terms of $0ħ\omega$ (nonintruder) configurations. This suggests that the energy differences between $0ħ\omega$ and $2ħ\omega$ configurations are large enough in ${}^{33}\mathrm{Si}$ and ${}^{34}\mathrm{P}$ that the low-lying $0ħ\omega$ states are not significantly perturbed.