Data di Pubblicazione:
2012
Citazione:
Low-lying dipole response : isospin character and collectivity in 68Ni, 132Sn and 208Pb / X. Roca-Maza, G. Pozzi, M. Brenna, K. Mizuyama, G. Colo'. - In: PHYSICAL REVIEW. C, NUCLEAR PHYSICS. - ISSN 0556-2813. - 85:2(2012), pp. 024601.1-024601.15. [10.1103/PhysRevC.85.024601]
Abstract:
The isospin character, the collective or single-particle nature, and the sensitivity to the slope of
the nuclear symmetry energy of the low-energy isovector dipole response (known as pygmy dipole
resonance) are nowadays under debate. In the present work we study, within the fully self-consistent
non-relativistic mean field (MF) approach based on Skyrme Hartree-Fock plus Random Phase Approximation
(RPA), the measured even-even nuclei 68Ni, 132Sn and 208Pb. To analyze the model
dependence in the predictions of the pygmy dipole strength, we employ three different Skyrme parameter
sets. We find that both the isoscalar and the isovector dipole responses of all three nuclei
show a low-energy peak that increases in magnitude, and is shifted to larger excitation energies,
with increasing values of the slope of the symmetry energy at saturation. We highlight the fact
that the collectivity associated with the RPA state(s) contributing to this peak is different in the
isoscalar and isovector case, or in other words it depends on the external probe. While the response
of these RPA states to an isovector operator does not show a clear collective nature, the response to
an isoscalar operator is recognizably collective, for all analyzed nuclei and all studied interactions.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
X. Roca-Maza, G. Pozzi, M. Brenna, K. Mizuyama, G. Colo'
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