Isospin-forbidden particle decays in light nuclei: (I). T = 32 levels of 9Be, 9B

Absolute branching ratios have been measured for the isospin-forbidden nucleon decays of the lowest $\text{T =}\text{3}\text{2}$ levels of ⁹Be and ⁹B to the ground state and first excited state of ⁸Be. The $\text{T =}\text{3}\text{2}$ levels were populated by the ⁷Li(³He, n) and ⁷Li(³He, p) reactions. The subsequent decay products were observed in coincidence with the neutrons or protons, detected at 0°. Branching ratios of 0.028 ± 0.021 and 0.50 ± 0.11 were determined for the neutron decays of the 14.39 MeV, $\text{T =}\text{3}\text{2}$ level of ⁹Be to the ground state and 2.9 MeV, 2⁺ first excited state of ⁸Be, respectively. Branching ratios of 0.11 ± 0.04 and 0.33 ± 0.09 were determined for the analogous proton decays of the ⁹B, 14.67 MeV $\text{T =}\text{3}\text{2}$ level. The similarity of the decay properties of these analogue levels is in contrast to the large asymmetries observed for $\text{T =}\text{3}\text{2}$ levels in other A = 4N + 1 light nuclei.