Mirror resonances in Be 9 and B 9 within an α + α + N model

Using an α + α + N three-body model, we describe the ground and excited unbound states above the three-body threshold of A = 9 mirror nuclei. We investigate the energy levels of low-lying and highly excited resonances below ≈ 10 MeV excitation energy of Be 9 and B 9 mirror nuclei with the complex-scaling method. The same number of solutions are found for both mirror nuclei, namely, thirteen resonances, 3 / 2 1 − 4 − , 5 / 2 1 − 3 − , 1 / 2 1 − 3 − , 7 / 2 1 , 2 − , and 9 / 2 − , including the ground state for odd parity states, and eight resonances 5 / 2 1 , 2 + , 3 / 2 1 , 2 + , 7 / 2 1 , 2 + , and 9 / 2 1 , 2 + , for even-parity states with the exception of the low-lying 1 / 2 + state. These results are compared with experimentally observed and other theoretically calculated results. The band structures of odd and even parity states for both Be 9 and B 9 mirror nuclei are discussed in relation to the effect of the Coulomb energy difference.