Electric dipole response of sd-shell nuclei within the Configuration-Interaction Shell Model approach

Abstract

Reliable theoretical predictions of nuclear dipole excitations are crucial for various nuclear applications, particularly in nuclear astrophysics. Calculations of radiative capture cross sections often rely on theoretical gamma strength functions, with the electric dipole response being the dominant component. We aim at a systematic description of the E1 strength of nuclei with mass numbers between 17 and 40 of interest for various applications and to better understand the nature of the low-energy dipole strength in neutron-rich nuclei, known as pygmy dipole resonances. We use the Configuration Interaction shell-model framework in the p-sd-pf valence space with a previously established empirical Hamiltonian. Systematic results of photoabsorption strength show good agreement with experimental data, provided a renormalization of the dipole operator is applied. Transition densities are computed in 26Ne and confirm the pure isovector character of the Giant Dipole Resonance. The strength at 7-10MeV is shown to have a distinct structure with largely fragmented wave functions and transition densities of isovector character at the edge of the nucleus. The Configuration Interaction shell model is proved to be a valuable tool in the description of the photoresponse of light nuclei, providing more accurate results than the usually employed approaches.

15 pages, 12 Figures

References in corpus (21)

• The Shell Model as Unified View of Nuclear Structure
• Neutron Star Structure and the Neutron Radius of 208Pb
• Complete electric dipole response and the neutron skin in 208Pb
• The neutron skin thickness from the measured electric dipole polarizability in ${}^{68}$Ni, ${}^{120}$Sn, and ${}^{208}$Pb
• Reference Database for Photon Strength Functions
• Pygmy Resonances and Neutron Skins
• Information content of the low-energy electric dipole strength: correlation analysis
• Low-energy isovector and isoscalar dipole response in neutron-rich nuclei
• Subtraction method in the second random--phase approximation: first applications with a Skyrme energy functional
• Decay Pattern of Pygmy States Observed in Neutron-Rich 26 Ne
• The Proton Electric Pygmy Dipole Resonance
• Low-energy dipole excitations in neon isotopes and N=16 isotones within the quasiparticle random phase approximation and the Gogny force
• Perturbative Approach to Effective Shell-Model Hamiltonians and Operators
• Second random-phase approximation with the Gogny force. First applications
• Low-lying Dipole Modes in ${}^{26,28}$Ne in the Quasiparticle Relativistic Random Phase Approximation
• Structure and decay of the pygmy dipole resonance in 26Ne
• Tests of the random phase approximation for transition strengths
• Transition sum rules in the shell model
• M1 resonance in ${}^{208}$Pb within the self-consistent phonon-coupling model
• Comparative analysis of formalisms and performances of three different beyond mean-field approaches
• Finite-temperature mean-field approximations for shell model Hamiltonians: the code HF-SHELL

Cited by in corpus (2)

• Modeling Ultra-High-Energy Cosmic Rays propagation using the input from Configuration Interaction Shell Model
• Electric dipole strength in $sd$-shell nuclei from small-angle proton scattering