Five-body resonances of 8He using the complex scaling method

The 0+ states of 8He are studied in a five-body He4+n+n+n+n cluster model. Many-body resonances are treated on the correct boundary condition as Gamow states using the complex scaling method. The 02+ state of 8He is predicted as a five-body resonance in the excitation energy of 6.3 MeV with a width of 3.2 MeV, which mainly has a (p3/2)2(p1/2)2 configuration. In this state, number of the 0+ neuron pair shows almost two, which is different from the ground state having a large amount of the 2+ pair component. The monopole transition of 8He from the ground state into the five-body unbound states is also evaluated. It is found that the He7+n component mostly exhausts the strength, while the 02+ contribution is negligible. The final states are dominated by He6+n+n, not He4+n+n+n+n. The results indicate the sequential breakup process of He8→He7+n→He6+n+n by the monopole excitation.