Abstract
Nuclear structure theory is considered in the framework of the development of a microscopic model for nucleon-capture astrophysical implementations. In particular, microscopically obtained strength functions from a theoretical method incorporating density functional theory and quasiparticle-phonon model are used as an input in a statistical reaction model. The approach is applied in systematic investigations of the impact of low-energy multipole excitations and pygmy resonances on dipole photoabsorption and radiative neutronand proton-capture cross sections of key s- and r-process nuclei which is discussed in comparison with the experiment. For the cases of the short-lived isotopes 89 Zr and 91 Mo theoretical predictions are made.
Highlights
The nuclear electromagnetic (EM) response at excitation energies below and around the neutron threshold is a complex admixture of nuclear excitations of different origin
Our approach, incorporating the energy-density functional (EDF) theory and the three-phonon quasiparticlephonon model (QPM), was the first to predict the existence of pygmy quadrupole resonance (PQR) as a natural extension of the already known pygmy dipole resonance (PDR) for higher multipole excitations [30]
The appearance of PDR is included (PDR in) the energy range below the neutron threshold is a general observation found in systematic EDF+QRPA and EDF+QPM calculations of the electric dipole response in different isotopic and isotonic chains of neutron-rich nuclei [5, 6, 9, 16, 17]
Summary
The nuclear electromagnetic (EM) response at excitation energies below and around the neutron threshold is a complex admixture of nuclear excitations of different origin. Among them of special importance are new modes of excitations called pygmy resonances which were theoretically predicted in medium and heavy nuclei with neutron excess and related to skin phenomena [1, 2]. Our approach, incorporating the energy-density functional (EDF) theory and the three-phonon QPM, was the first to predict the existence of pygmy quadrupole resonance (PQR) as a natural extension of the already known PDR for higher multipole excitations [30]. These PQR states have been detected for the first time experimentally in 124S n nucleus via the (17O,17O’γ) reaction [31]. The proton radiative capture reaction 89Y(p,γ)90Zr for which experimental data exist, is studied to test the newly derived SF [25]
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