Accueil du site > Publications récentes > Electric dipole strength and dipole polarizability in 48Ca within a fully self-consistent second random–phase approximation
D. Gambacurta, M. Grasso, O. Vasseur
The second random–phase–approximation model corrected by a subtraction
procedure designed to cure double counting, instabilities, and
ultraviolet divergences, is employed for the first time to analyze the
dipole strength and polarizability in 48Ca. All the terms of
the residual interaction are included, leading to a fully
self-consistent scheme. Results are illustrated with two Skyrme
parametrizations, SGII and SLy4. Those obtained with the SGII
interaction are particularly satisfactory. In this case, the low-lying
strength below the neutron threshold is well reproduced and the giant
dipole resonance is described in a very satisfactory way especially in
its spreading and fragmentation. Spreading and fragmentation are
produced in a natural way within such a theoretical model by the
coupling of 1 particle-1 hole and 2 particle-2 hole configurations.
Owing to this feature, we may provide for the electric polarizability as
a function of the excitation energy a curve with a similar slope around
the centroid energy of the giant resonance compared to the
corresponding experimental results. This represents a considerable
improvement with respect to previous theoretical predictions obtained
with the random–phase approximation or with several ab-initio
models. In such cases, the spreading width of the excitation cannot be
reproduced and the polarizability as a function of the excitation energy
displays a stiff increase around the predicted centroid energy of the
giant resonance.
Voir en ligne : Physics Letters B, 777, 163 (2018)
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