Extended Theory of Finite Fermi Systems: Application to the collective and non-collective E1 strength in ${}^{208}$Pb

Abstract

The Extended Theory of Finite Fermi Systems is based on the conventional Landau-Migdal theory and includes the coupling to the low-lying phonons in a consistent way. The phonons give rise to a fragmentation of the single-particle strength and to a compression of the single-particle spectrum. Both effects are crucial for a quantitative understanding of nuclear structure properties. We demonstrate the effects on the electric dipole states in ${}^{208}$Pb (which possesses 50% more neutrons then protons) where we calculated the low-lying non-collective spectrum as well as the high-lying collective resonances. Below 8 MeV, where one expects the so called isovector pygmy resonances, we also find a strong admixture of isoscalar strength that comes from the coupling to the high-lying isoscalar electric dipole resonance, which we obtain at about 22 MeV. The transition density of this resonance is very similar to the breathing mode, which we also calculated. We shall show that the extended theory is the correct approach for self-consistent calculations, where one starts with effective Lagrangians and effective Hamiltonians, respectively, if one wishes to describe simultaneously collective and non-collective properties of the nuclear spectrum. In all cases for which experimental data exist the agreement with the present theory results is good.

arXiv comment21 figures corrected typos in author field

References in corpus (7)

• Large-scale QRPA calculation of E1-strength and its impact on the neutron capture cross section
• Extended Theory of Finite Fermi Systems (Collective Vibrations in Closed Shell Nuclei)
• Dipole states in stable and unstable nuclei
• Probing the Nuclear Neutron Skin by Low-Energy Dipole Modes
• Effective-range approach and scaling laws for electromagnetic strength in neutron-halo nuclei
• Pygmy Dipol Resonances as a Manifestation of the Structure of the Neutron-Rich Nuclei
• Landau Migdal Theory of Interacting Fermi Systems: A Framework for Effective Theories in Nuclear Structure Physics

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• Coupling charge-exchange vibrations to nucleons in a relativistic framework: effect on Gamow-Teller transitions and beta-decay half-lives
• Pygmy and Giant Dipole Resonances by Coulomb Excitation using a Quantum Molecular Dynamics model
• Evolution of the pygmy dipole resonance in nuclei with neutron excess
• Nuclear response theory with multiphonon coupling in a covariant framework
• Microscopic description of the pygmy and giant electric dipole resonances in stable Ca isotopes
• Pion-nucleon correlations in finite nuclei in a relativistic framework: effects on the shell structure
• Self-consistent calculations within the Extended Theory of Finite Fermi Systems
• Isospin transfer modes in exotic nuclei