Investigation of Pygmy Dipole Resonances in the Tin Region

Abstract

The evolution of the low-energy electromagnetic dipole response with the neutron excess is investigated along the Sn isotopic chain within an approach incorporating Hartree-Fock-Bogoljubov (HFB) and multi-phonon Quasiparticle-Phonon-Model (QPM) theory. General aspects of the relationship of nuclear skins and dipole sum rules are discussed. Neutron and proton transition densities serve to identify the Pygmy Dipole Resonance (PDR) as a generic mode of excitation. The PDR is distinct from the GDR by its own characteristic pattern given by a mixture of isoscalar and isovector components. Results for the ${}^{100}$Sn-${}^{132}$Sn isotopes and the several N=82 isotones are presented. In the heavy Sn-isotopes the PDR excitations are closely related to the thickness of the neutron skin. Approaching ${}^{100}$Sn a gradual change from a neutron to a proton skin is found and the character of the PDR is changed correspondingly. A delicate balance between Coulomb and strong interaction effects is found. The fragmentation of the PDR strength in ${}^{124}$Sn is investigated by multi-phonon calculations. Recent measurements of the dipole response in ${}^{130,132}$Sn are well reproduced.

41 pages, 10 figures, PRC

References in corpus (2)

• Exotic modes of excitation in atomic nuclei far from stability
• Pygmy dipole resonance as a constraint on the neutron skin of heavy nuclei

Cited by in corpus (30)

• Isospin Character of the Pygmy Dipole Resonance in 124Sn
• Reference Database for Photon Strength Functions
• Pygmy Resonances and Neutron Skins
• Relativistic quasiparticle time blocking approximation. Dipole response of open-shell nuclei
• Pygmy dipole strength in 90Zr
• Large-scale deformed quasiparticle random-phase approximation calculations of the $\gamma$-ray strength function using the Gogny force
• Low-lying dipole response in the Relativistic Quasiparticle Time Blocking Approximation and its influence on neutron capture cross sections
• Relativistic quasiparticle time blocking approximation. II. Pygmy dipole resonance in neutron-rich nuclei
• Low-energy electric dipole response in 120Sn
• Low-energy dipole strength in 112,120Sn
• Population of dipole states via isoscalar probes: the splitting of pygmy dipole resonance in ${}^{124}$Sn}
• Self-consistent calculations of the strength function and radiative neutron capture cross section for stable and unstable tin isotopes
• Pygmy and core polarization dipole modes in ${}^{206}$Pb: connecting nuclear structure to stellar nucleosynthesis
• Electric and magnetic dipole strength in 112,114,116,118,120,124Sn
• A self-consistent study of multipole response in neutron-rich nuclei using a modified realistic potential
• Quasiparticle Random Phase Approximation with Interactions from the Similarity Renormalization Group
• Accessing the Single-Particle Structure of the Pygmy Dipole Resonance in ${}^{208}$Pb
• Evolution of the dipole polarizability in the stable tin isotope chain
• Nature of low-lying electric dipole resonance excitations in 74Ge
• Systematics of the low-energy electric dipole strength in the Sn isotopic chain
• Experimental study of excited states of ${}^{62}$Ni via one-neutron $(d,p)$ transfer up to the neutron-separation threshold and characteristics of the pygmy dipole resonance states
• Effects of phonon-phonon coupling on properties of pygmy resonance in ${}^{124-132}$Sn
• Charge-exchange dipole excitations in neutron-rich nuclei: $-1\hslash {\omega }_0$, anti-analog pygmy, and anti-analog giant resonances
• Nuclear breathing mode in neutron-rich Nickel isotopes: sensitivity to the symmetry energy and the role of the continuum
• Emergence of low-energy monopole strength in the neutron-rich calcium isotopes
• Nuclear collective dynamics within Vlasov approach
• Instantaneous Shape Sampling - a model for the $\gamma$-absorption cross section of transitional nuclei
• Benchmark of many-body approaches for magnetic dipole transition strength
• Low-energy monopole strength in spherical and deformed nuclei : cluster and soft modes
• Effective restoration of dipole sum rules within the renormalized random-phase approximation