Virtual-state character of the 9Be 1/2+ state in the 9Be(γ,n)8Be reaction

We study the character of the first excited 1/2(+) state of Be-9, which is observed as a low-lying sharp peak in the cross section of Be-9(gamma,n)2(4)He just above the Be-8 + n threshold. Using the alpha + alpha + n three-body model, we describe the ground and excited unbound states of Be-9 above the alpha + alpha + n threshold. Applying the complex scaling method to the three-body model, we find no 1/2(+) resonant solutions with the scaling angle of theta <= 15 degrees, while the low-lying peak in the photodisintegration cross section is reproduced in the present calculation. It is found that the Be-8 + n continuum states dominate the low-lying peak in the cross section. Furthermore, using the analytical continuation of the coupling constant of the three-body interaction for the alpha + alpha + n system, we discuss the virtual-state character of the 1/2(+) state.