Unexpected spin-parity assignments of the excited states in 9Be.

The excited states in the light nucleus 9Be are studied through β-delayed neutron decays from spin-polarized 9Lig.s.. The neutron transitions via 5Heg.s. from the 2.43-, 2.78-, 4.704-, 5.59-, and 7.94-MeV states in 9Be are observed for the first time, and the spins and parities (Iπ's) of the excited states in 9Be are assigned from β-n coincidences and measurements of the β-decay asymmetries. The spin parity, Iπ, 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 Iπ 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 Iπ values of the 2.78- and 4.704-MeV states. [ABSTRACT FROM AUTHOR]