Evolution of the pygmy dipole resonance in nuclei with neutron excess

Abstract

The electric dipole excitation of various nuclei is calculated with a Random Phase Approximation phenomenological approach. The evolution of the strength distribution in various groups of isotopes, oxygen, calcium, zirconium and tin, is studied. The neutron excess produces $E1$ strength in the low energy region. Indexes to measure the collectivity of the excitation are defined. We studied the behavior of proton and neutron transition densities to determine the isoscalar or isovector nature of the excitation. We observed that in medium-heavy nuclei the low-energy $E1$ excitation has characteristics rather different that those exhibited by the giant dipole resonance. This new type of excitation can be identified as pygmy dipole resonance.

arXiv comment14 pages, 12 figures, 7 tables

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Cited by in corpus (18)

• Nuclear Equation of State from ground and collective excited state properties of nuclei
• Pygmy dipole resonance in 208Pb
• Impact of tensor force on β-decay of magic and semi-magic nuclei
• Low-lying dipole response in the stable ${}^{40,48}$Ca nuclei with the second random-phase approximation
• Low-energy dipole strength in 112,120Sn
• Tensor effective interaction in self-consistent Random Phase Approximation calculations
• Low-energy dipole excitations in neon isotopes and N=16 isotones within the quasiparticle random phase approximation and the Gogny force
• Connecting the Pygmy Dipole Resonance to the neutron skin
• Pygmy and Giant Dipole Resonances by Coulomb Excitation using a Quantum Molecular Dynamics model
• Self-consistent Continuum Random Phase Approximation calculations with finite-range interactions
• Quasiparticle Random Phase Approximation with Interactions from the Similarity Renormalization Group
• Pygmy dipole resonance: collective features and symmetry energy effects
• Isoscalar dipole coherence at low energies and forbidden E1 strength
• Isovector and isoscalar dipole excitations in ${}^9$Be and ${}^{10}$Be studied with antisymmetrized molecular dynamics
• Dipole response in neutron-rich nuclei with new Skyrme interactions
• Low-energy dipole strength and the critical case of 48Ca
• Pygmy and giant electric dipole responses of medium-heavy nuclei in a self-consistent Random Phase Approximation approach with finite-range interaction
• Magnetic excitations in nuclei with neutron excess