On the importance of using exact pairing in the study of pygmy dipole resonance

Abstract

The strength functions of giant dipole resonance (GDR) in oxygen ${}^{18-24}$O, calcium ${}^{50-60}$Ca, and tin ${}^{120-130}$Sn isotopes are calculated within the phonon damping model under three approximations: without superfluid pairing, including BCS pairing, and exact pairing gaps. The analysis of the numerical results shows that exact pairing decreases the two-neutron separation energy in light nuclei, but increases it in heavy nuclei as compared to that obtained within the BCS theory. In neutron-rich medium and heavy nuclei, exact pairing significantly enhances the strength located at the low-energy tail of the GDR, which is usually associated with the pygmy dipole resonance. The line shape of the GDR changes significantly with increasing the neutron number within an isotopic chain if the model parameter is kept fixed at the value determined for the stable isotope.

26 pages, 19 figures, to appear in Journal of Physics G

References in corpus (8)

• Canonical-basis time-dependent Hartree-Fock-Bogoliubov theory and linear-response calculations
• Self-consistent description of multipole strength: systematic calculations
• Emergence of pygmy dipole resonances: Magic numbers and neutron skins
• Low-lying dipole response in the stable ${}^{40,48}$Ca nuclei with the second random-phase approximation
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• Self-consistent Skyrme QRPA for use in axially-symmetric nuclei of arbitrary mass
• Exact and approximate ensemble treatments of thermal pairing in a multilevel model
• Search for low lying dipole strength in the neutron rich nucleus ${}^{26}$Ne

Cited by in corpus (6)

• Finite amplitude method applied to giant dipole resonance in heavy rare-earth nuclei
• Magnetic dipole excitations based on the relativistic nuclear energy density functional
• Magnetic dipole excitation and its sum rule in nuclei with two valence nucleons
• The evolution of magnetic dipole strength in ${}^{100-140}$ Sn isotope chain and quenching of nucleon g factors
• Effective restoration of dipole sum rules within the renormalized random-phase approximation
• Possible existence of pygmy dipole resonance built on excited states in a neutron-rich ${}^{80}$Ge nucleus