Non-iterative finite amplitude methods for E1 and M1 giant resonances

TL;DR

This paper applies the finite amplitude method (FAM) to efficiently compute E1 and M1 giant resonances in nuclei, demonstrating good agreement with experimental data and highlighting areas for further refinement.

Contribution

It rederives RPA matrices for Skyrme functionals using FAM and analyzes giant resonances, providing a computationally efficient approach and insights into residual interactions.

Findings

FAM accurately reproduces E1 resonance energies in heavy nuclei.

Residual interactions do not affect M1 transition strengths in double-magic nuclei.

Neglecting spin terms in Skyrme forces may limit M1 transition accuracy.

Abstract

The finite amplitude method (FAM) is a very efficient approach for solving the fully self-consistent random-phase approximation (RPA) equations. We use FAM to rederive the RPA matrices for general Skyrme-like functionals, calculate the electric dipole (E1) and the magnetic dipole (M1) giant resonances, and compare the results with available experimental and evaluated data. For the E1 transitions in heavy nuclei, the calculations reproduce well the resonance energy of the photoabsorption cross sections. In the case of M1 transitions, we show that the residual interaction does not affect the transition strength of double-magic nuclei, which suggests that the spin terms in the Skyrme force currently neglected in the present computation could improve the agreement between FAM and experimental data.