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.

14 pages, 12 figures, 7 tables

References in corpus (6)

• Exotic modes of excitation in atomic nuclei far from stability
• Pygmy dipole resonance as a constraint on the neutron skin of heavy nuclei
• Relativistic RPA plus phonon-coupling analysis of pygmy dipole resonances
• Extended Theory of Finite Fermi Systems: Application to the collective and non-collective E1 strength in ${}^{208}$Pb
• Self-consistent calculations within the Green's function method including particle-phonon coupling and the single-particle continuum
• Pygmy dipole resonance in exotic nuclei

Cited by in corpus (7)

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• 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
• Quasiparticle Random Phase Approximation with Interactions from the Similarity Renormalization Group
• Self-consistent Continuum Random Phase Approximation calculations with finite-range interactions
• Pygmy and Giant Dipole Resonances by Coulomb Excitation using a Quantum Molecular Dynamics model
• Isoscalar dipole coherence at low energies and forbidden E1 strength