Optimizing artificial neural networks for dipole strength predictions in light nuclei

Abstract

We present an optimized artificial neural network approach for predicting electric dipole strength functions in nuclei with $A < 50$. Building upon a previous global study [Phys.Rev.C $\textbf{111}$ (2025) 5, L051308], we focus here on the region of light nuclei where dipole responses are more structured. The new network incorporates a two-stage training process, a learned embedding of the proton number, explicit low-energy dipole onsets, uncertainty-weighted training, and high-energy regularization. Ensemble predictions show improved stability and substantially reduced variability across independently initialized networks compared with the earlier global neural network. Tests on selected isotopes withheld from training show that, for elements represented in the training set, the optimized network captures the main isotope dependent dipole strength systematics. As a further test, we compute electric dipole polarizabilities for selected light nuclei and compare them with literature values revealing a pronounced sensitivity to the covered energy interval. The resulting set of continuous electric dipole strength functions for nuclei with $A < 50$ provides a practical complement to existing tabulated photonuclear databases and is particularly suited for applications requiring smooth response functions over broad energy intervals. As an application, we provide an update on the electric dipole polarizability of $^9$Be.