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

TL;DR

This study investigates the nature of the first excited 1/2^{+} state in {9}^Be, revealing it as a virtual state dominated by the {8}^Be+n component, using a three-body model and complex scaling method.

Contribution

The paper introduces a three-body model combined with complex scaling to analyze the virtual-state character of the {9}^Be 1/2^{+} state, providing new insights into its structure.

Findings

No 1/2^{+} resonant solutions found with complex scaling.

Low-lying peak explained mainly by {8}^Be+n component.

The 1/2^{+} state exhibits virtual-state character.

Abstract

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({\gamma},n)2{\alpha} just above the {8}^Be+n threshold. Using the {\alpha}+{\alpha}+n three-body model, we describe the ground and excited unbound states of {9}^Be above the {\alpha}+{\alpha}+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 {\alpha}+{\alpha}+n system, we discuss the virtual-state character of the 1/2^{+} state.