High-spin structure of thesdshell nucleiNa25andNe22

Abstract

The level structure of $^{25}\mathrm{Na}$ and $^{22}\mathrm{Ne}$ in the high excitation energy/high spin regime was studied using $\ensuremath{\gamma}$-ray spectroscopy and Doppler shift lifetime measurements following $^{12}\mathrm{C}(^{18}\mathrm{O},\ensuremath{\alpha}p)^{25}\mathrm{Na}$ and $^{12}\mathrm{C}(^{18}\mathrm{O},2\ensuremath{\alpha})^{22}\mathrm{Ne}$ reactions. Multiple new levels and transitions were identified in both nuclides based on $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidence data. In $^{25}\mathrm{Na}$, evidence was found for higher-spin negative-parity states up to ${I}^{\ensuremath{\pi}}=13/{2}^{\ensuremath{-}}$ resulting from neutron excitation into the $pf$ shell, in good agreement with shell model calculations using the SDPF-MU and FSU interactions. Candidates for the yrast ${7}^{+}$ and ${8}^{+}$ levels in $^{22}\mathrm{Ne}$, consistent with calculations using the USDB interaction, were also identified.