Low-energy isovector and isoscalar dipole response in neutron-rich nuclei

Vretenar, Dario and Niu, Y. F. and Paar, Nils and Meng, Jie (2012) Low-energy isovector and isoscalar dipole response in neutron-rich nuclei. Physical Review C, 85 (4). pp. 44317-8. ISSN 0556-2813

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Abstract

The self-consistent random-phase approximation, based on the framework of relativistic energy density functionals, is employed in the study of isovector and isoscalar dipole response in 68Ni, 132Sn, and 208Pb. The evolution of pygmy dipole states (PDSs) in the region of low excitation energies is analyzed as a function of the density dependence of the symmetry energy for a set of relativistic effective interactions. The occurrence of PDSs is predicted in the response to both the isovector and the isoscalar dipole operators, and its strength is enhanced with the increase in the symmetry energy at saturation and the slope of the symmetry energy. In both channels, the PDS exhausts a relatively small fraction of the energy-weighted sum rule but a much larger percentage of the inverse energy-weighted sum rule. For the isovector dipole operator, the reduced transition probability B(E1) of the PDSs is generally small because of pronounced cancellation of neutron and proton partial contributions. The isoscalar-reduced transition amplitude is predominantly determined by neutron particle-hole configurations, most of which add coherently, and this results in a collective response of the PDSs to the isoscalar dipole operator.

Item Type: Article
Keywords: nuclear energy density functional, dipole response, quasiparticle random phase approximation
Date: April 2012
Subjects: NATURAL SCIENCES > Physics > Nuclear Physics
Additional Information: Copyright (2012) by the American Physical Society.
Divisions: Faculty of Science > Department of Physics
Project code: 119-1191005-1010
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 09 Jun 2014 12:47
Last Modified: 23 Feb 2016 16:11
URI: http://digre.pmf.unizg.hr/id/eprint/2164

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