Identification and lifetime determination of the6+member of the ground-state rotational band inNe22

Abstract

The $^{19}\mathrm{F}(\ensuremath{\alpha},p\ensuremath{\gamma})^{22}\mathrm{Ne}$ reaction was used to measure $p\ensuremath{-}\ensuremath{\gamma}$ angular correlations for the 6.31 and 6.34 MeV states in $^{22}\mathrm{Ne}$. The mean lifetimes of the two levels were determined to be 78 \ifmmode\pm\else\textpm\fi{} 15 fs (6.31 MeV) and ${24}_{\ensuremath{-}17}^{+15}$ fs (6.34 MeV) using the same reaction and the Doppler-shift attenuation method. Unambiguous spin and parity assignments of ${6}^{+}$ and ${4}^{+}$ were obtained for the 6.31 and 6.34 MeV states, respectively. An earlier identification of the 6.34 MeV state as the ${6}^{+}$ member of the ground state rotational band is therefore incorrect. The $B(E2)$ value of the 6.31 MeV (${6}^{+}$) \ensuremath{\rightarrow} 3.36 MeV (${4}^{+}$) transition is in good agreement with recent large-basis shell model calculations, and the 6.31 MeV state may be identified as the ${6}^{+}$ member of the ground state rotational band of $^{22}\mathrm{Ne}$.NUCLEAR REACTIONS $^{19}\mathrm{F}(\ensuremath{\alpha},p\ensuremath{\gamma})$, ${E}_{\ensuremath{\alpha}}=12.0, 15.15$ MeV; measured $p\ensuremath{-}\ensuremath{\gamma}$ angular correlations, Doppler-shift attenuation. $^{22}\mathrm{Ne}$ deduced levels, $\ensuremath{\tau}$, $J$, $\ensuremath{\pi}$, $B (\ensuremath{\Lambda})$.