Analysis of the energy and angular distributions of photoneutrons from natPb, 197Au, natSn, natCu, natFe, and natTi using resonance direct theory

TL;DR

This study models photoneutron emissions from various elements in the GDR region, emphasizing the role of resonance direct processes and validating the model with experimental data.

Contribution

It applies Wilkinson's resonance direct theory combined with other models to describe neutron emissions, providing insights into the emission mechanisms and angular distributions.

Findings

Good agreement between calculations and experimental data for Pb, Au, and Sn.

Resonance direct process significantly contributes at high neutron energies.

The model enhances understanding of photoneutron emission mechanisms in the GDR region.

Abstract

Photoneutron double-differential cross sections in the giant dipole resonance (GDR) region were calculated to investigate the underlying nuclear reaction mechanisms, with particular emphasis on the role of the direct process. Contributions from direct, pre-equilibrium, and compound processes were all taken into account. Wilkinson's resonance direct (RD) theory, based on the independent particle model, was applied to describe high-energy neutron emission from the direct process. The angular distribution of neutrons emitted via the RD mechanism was formulated using the Agodi and Courant formalism, which was incorporated into the RD framework. Neutron emission from the pre-equilibrium and compound processes was calculated using the two-component exciton model and the Hauser-Feshbach formalism, respectively. The calculated results were compared with experimental data obtained at NewSUBARU using 16.6-MeV quasi-monochromatic linearly-polarized photon beams. Good agreement between calculations and measurements was observed for Pb, Au, and Sn, confirming the validity of the proposed model. Furthermore, the angular anisotropies of photoneutrons emitted from these elements were investigated, revealing considerable contributions from the RD process at high neutron energies. This study provides a deeper understanding of photoneutron emission mechanisms in the GDR energy region.