Pygmy dipole resonances in the tin region
- Institut fuer Theoretische Physik, Universitaet Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen (Germany)
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 multiphonon 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 {sup 100}Sn-{sup 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 {sup 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 {sup 124}Sn is investigated by multiphonon calculations. Recent measurements of the dipole response in {sup 130,132}Sn are well reproduced.
- OSTI ID:
- 21068126
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 77, Issue 2; Other Information: DOI: 10.1103/PhysRevC.77.024321; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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