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The virtual-state character of the {9}^Be 1/2^+ state in the {9}^Be(γ,n){8}^Be reaction

We study the character of the first excited 1/2^{+} state of {9}^Be, which is observed as a low-lying sharp peak in the cross section of 9^Be(γ,n)2α just above the {8}^Be+n threshold. Using the α+α+n three-body model, we describe the ground and excited unbound states of {9}^Be above the α+α+n threshold. Applying the complex scaling method to the three-body model, we find no 1/2^{+} resonant solutions, while the low-lying peak in the photodisintegration cross section is reproduced in the present calculation. It is found that the low-lying peak is dominantly explained by the 8^Be+n component. Furthermore, using the analytical continuation of the coupling constant of the three-body interaction for the α+α+n system, we discuss the virtual-state character of the 1/2^{+} state.