Nuclear symmetry energy and neutron skins derived from pygmy dipole resonances

Klimkiewicz, A. and Paar, Nils and Adrich, P. and Fallot, M. and Boretzky, K. and Aumann, T. and Cortina-Gil, D. and Pramanik, U. Datta and Elze, Th. W. and Emling, H. and Geissel, H. and Hellström, M. and Jones, K. L. and Kratz, J. V. and Kulessa, R. and Nociforo, C. and Palit, R. and Simon, H. and Surowka, G. and Summerer, K. and Vretenar, Dario and Walus, W. (LAND Collaboration) (2007) Nuclear symmetry energy and neutron skins derived from pygmy dipole resonances. Physical Review C, 76 (5). pp. 51603-4. ISSN 0556-2813

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By exploiting Coulomb dissociation of high-energy radioactive beams of the neutron-rich nuclei 129-132Sn and 133, 134Sb, their dipole-strength distributions have been measured. A sizable fraction of "pygmy" dipole strength, energetically located below the giant dipole resonance, is observed in all of these nuclei. A comparison with available pygmy resonance data in stable nuclei (208Pb and N=82 isotones) indicates a trend of strength increasing with the proton-to-neutron asymmetry. On theoretical grounds, employing the RQRPA approach, a one-to-one correlation is found between the pygmy strength and parameters describing the density dependence of the nuclear symmetry energy, and in turn with the thicknesses of the neutron skins. On this basis, by using the experimental pygmy strength, parameters of the nuclear symmetry energy (a4=32.0± ; 1.8 MeV and po=2.3± ; 0.8 MeV/fm3) are deduced as well as neutron-skin thicknesses Rn-Rp of 0.24± ; 0.04 fm for 132Sn and of 0.18± ; 0.035 fm for 208Pb, both doubly magic nuclei. Astrophysical implications with regard to neutron stars are briefly addressed.

Item Type: Article
Keywords: nuclear giant resonances, reactions induced by unstable nuclei, Coulomb excitation by heavy ions
Date: November 2007
Subjects: NATURAL SCIENCES > Physics > Nuclear Physics
Additional Information: Copyright (2007) 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: 24 May 2014 19:46
Last Modified: 28 Aug 2014 15:31

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