The excited states in the light nucleus ${}^9\mathrm{Be}$ are studied through $\beta$-delayed neutron decays from spin-polarized ${}^9{\mathrm{Li}}_{\mathrm{g}.\mathrm{s}.}$. The neutron transitions via ${}^5{\mathrm{He}}_{\mathrm{g}.\mathrm{s}.}$ from the 2.43-, 2.78-, 4.704-, 5.59-, and 7.94-MeV states in ${}^9\mathrm{Be}$ are observed for the first time, and the spins and parities ($I^{\pi }$'s) of the excited states in ${}^9\mathrm{Be}$ are assigned from $\beta \text{−}n$ coincidences and measurements of the $\beta$-decay asymmetries. The spin parity, $I^{\pi }$, of the 2.43-MeV state is assigned to be $5/2^{-}$, which is consistent with the reported value. The present results suggest that the $I^{\pi }$ values of the 2.78-, 4.704-, 5.59-, and 7.94-MeV states are $3/2^{-}$, $1/2^{-}$, $5/2^{-}$, and $3/2^{-}$, respectively, which are different from early reported values. However, shell-model calculations of the $p$ shell are in overall good agreement with the present results, except for the $I^{\pi }$ values of the 2.78- and 4.704-MeV states.

• Received 16 December 2014
• Revised 9 February 2015

DOI:https://doi.org/10.1103/PhysRevC.91.024328