Azimuthal angle distributions of neutrons emitted from the ⁹Be(γ,n) reaction with linearly polarized γ-rays

The electromagnetic transitions of $^9$Be with linearly polarized $\gamma$-rays are calculated by using the $\alpha$~+~$\alpha$~+~$n$ three-body model and the complex-scaled solutions of the Lippmann-Schwinger equation; the azimuthal angle distributions of the emitted neutrons are investigated. We calculate the anisotropy parameter as a function of the photon incident energy $E_\gamma$, and discuss how sensitive the anisotropy parameter is to nuclear structure and transition modes. The result suggests that the azimuthal angle distribution of neutrons emitted from the $^9$Be($\gamma$,$n$) reaction with the linearly polarized $\gamma$-rays is useful to identify the resonances in the final states even if it is not clearly observed in the cross section.