Spectroscopy ofNe32and the “Island of Inversion”

Abstract

We report on the first spectroscopic study of the $N=22$ nucleus ${}^{32}\mathrm{Ne}$ at the newly completed RIKEN Radioactive Ion Beam Factory. A single $\gamma$-ray line with an energy of 722(9) keV was observed in both inelastic scattering of a $226\mathrm{MeV}/u$ ${}^{32}\mathrm{Ne}$ beam on a carbon target and proton removal from ${}^{33}\mathrm{Na}$ at $245\mathrm{MeV}/u$. This transition is assigned to the deexcitation of the first $J^{\pi }=2^{+}$ state in ${}^{32}\mathrm{Ne}$ to the $0^{+}$ ground state. Interpreted through comparison with state-of-the-art shell-model calculations, the low excitation energy demonstrates that the “island of inversion” extends to at least $N=22$ for the Ne isotopes.