Abstract
Background: The pygmy dipole resonance (PDR) is an interesting nuclear
structure phenomenon with an impact in predicting different astrophysics
scenarios, for example, specific properties of neutron stars that can be
determined from the thickness of the neutron skin which is directly
connected to the strength of the PDR. Various collective and microscopic
models were employed in order to account for the observed properties of
the PDR.
Purpose: Determine for the first time whether it is possible to use the
interacting boson approximation (IBA) to reproduce the general
characteristics of the PDR.
Methods: The PDR properties of the stable even-even N = 82 isotones are
calculated in the IBA-spdf model based on the assumption that many
effects of the mixing caused by the shell structure can be simulated by
considering the number of bosons as an effective value.
Results: The IBA calculations indicate a resonance-like structure of the
E1 strength in the energy region 5-8 MeV, thus confirming the
experimental results for this mass region. The distribution and
fragmentation of the J(pi) = 1(-) states and of the E1 strength are in
good agreement with the experimental data. By employing the same
procedure as for the N = 82 isotones, the model is used to predict the
PDR strength for a nucleus in a different mass region, i.e., for the
Mo-94 nucleus.
Conclusions: The calculations confirm a good agreement for the
distribution and fragmentation of the E1 strength.
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