Three-body description of 9C: Role of low-lying resonances in breakup reactions
Abstract
The 9C nucleus and related capture reaction, 8B(p,γ)9C, have been intensively studied with an astrophysical interest. Due to the weakly-bound nature of 9C, its structure is likely to be described as the three-body (7Be+p+p). Its continuum structure is also important to describe reaction processes of 9C, with which the reaction rate of the 8B(p,γ)9C process have been extracted indirectly. We perform three-body calculations on 9C and discuss properties of its ground and low-lying states via breakup reactions. We employ the three-body model of 9C using the Gaussian-expansion method combined with the complex-scaling method. This model is implemented in the four-body version of the continuum-discretized coupled-channels method, by which breakup reactions of 9C are studied. The intrinsic spin of 7Be is disregarded. By tuning a three-body interaction in the Hamiltonian of 9C, we obtain the low-lying 2+ state with the resonant energy 0.781 MeV and the decay width 0.137 MeV, which is consistent with the available experimental information and a relatively high-lying second 2+ wider resonant state. Our calculation predicts also sole 0+ and three 1- resonant states. We discuss the role of these resonances in the elastic breakup cross section of 9C on 208Pb at 65 and 160 MeV/A. The low-lying 2+ state is probed as a sharp peak of the breakup cross section, while the 1- states enhance the cross section around 3 MeV. Our calculations will further support the future and ongoing experimental campaigns for extracting astrophysical information and evaluating the two-proton removal cross-sections.