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Systematic studies of M1 photon strength functions with Skyrme-HFB+QRPA and the derived total dipole (E1+M1) resonance properties

par Xu, Yi ;Goriely, Stéphane ;Krticka, M.;Khan, Elias
Référence Physical review. C. Nuclear physics, 113, page (014306)
Publication Publié, 2026-01-07

Article révisé par les pairs

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Résumé :

The photon strength function (PSF) of nuclear dipole excitation is greatly important to different applications especially including nuclear astrophysics. However, for the ≈10 000 nuclei over the whole nuclear chart, the total electric dipole (E1) and magnetic dipole (M1) PSF directly derived from large-scale calculation with microscopic theory is not available yet. In this paper, we perform a systematic study on the M1 PSF based on the microscopic Hartree-Fock-Bogoliubov plus quasiparticle random-phase approximation (HFB+QRPA) model used in our previous work of the E1 PSF. In particular, large-scale calculations of the spin-flip M1 strength distributions are performed in the framework of HFB+QRPA under the assumption of spherical symmetry using the BSk27 Skyrme effective interaction. The spin-flip M1 PSFs are obtained by folding the QRPA strength distributions with a Lorentz function that describes the damping of nuclear collective motion empirically. The scissors mode and the low-energy upbend contribution to the M1 PSFs are both added phenomenologically to the spin-flip component. The resulting BSk27+QRPA M1 PSF is shown to be in fairly good agreement with available experimental data. In addition, the comparison between our BSk27+QRPA M1 PSF and other theoretical results indicates that the present approach provides an efficient and reliable alternative to describe the M1 PSF for a large set of nuclei. When consistently considering both our previous E1 and the present M1 BSk27+QRPA PSFs, predictions reasonably reproduce multistep γ -ray cascade spectra, average radiative widths, and Maxwellian-averaged cross sections. A complete set of E1 and M1 PSFs are determined for ≈10 000 nuclei with 8 ≼ Z ≼ 124 lying between the proton and the neutron drip lines and used to estimate astrophysical neutron capture rates that are found to be comparable to those obtained with the previous Gogny-HFB + QRPA predictions based on the D1M interaction.