Pygmy resonances and radiative nucleon captures for stellar nucleosynthesis

Abstract

The impact of low-energy multipole excitations and pygmy resonances on radiative neutron and proton-capture cross sections in nuclei close to the β-stability line is investigated. For this purpose, a microscopic theoretical approach based on self-consistent density functional theory and quasiparticle-random-phase-approximation formalism extended with multiphonon degrees of freedom is implemented in a statistical reaction model. The advantage of the method is the microscopic nuclear structure input for unified description of low-energy multiphonon excitations and pygmy and giant resonances. This is found to be important for the understanding of the fine structure and dynamics of the nuclear response function at low energies, which strongly influences nuclear reaction rates of astrophysical relevance.

Decay of quadrupole-octupole1−states inCa40andCe140Derya1, Tsoneva2, Aumann3 et al. 2016Phys. Rev. CSelf Cite12120View full textAdd to dashboardCite

“…These include the low-energy tail of the IVGDR, PDR [18,19,27,28], multi-phonon excitations [19,29], toroidal modes [23] and α-cluster vibrations [30,31]. Furthermore, in recent studies it has been pointed out that the interaction between quasiparticles and phonons is important for a correct theoretical description of the low-lying E1 strength because it can influence its fragmentation and mixing with the core polarization and the IVGDR [18,19,29,[32][33][34][35]. This affects strongly the electromagnetic strength distribution, which can have further consequences on the dipole polarizability and nucleosynthesis processes [29,34,36].…”

Influence of complex configurations on the properties of the pygmy dipole resonance in neutron-rich Ca isotopes

“…This is achieved by solving the groundstate problem in a semi-microscopic approach based on a Skyrme energy density functional (EDF) [26,27]. The EDF+QPM calculations have been applied for calculating the low-energy dipole strength [26,27], as well as used for astrophysical applications [28]. The results indicate that the radiative capture cross sections are underestimated by a factor of about two by the QRPA for the N = 50 nuclei.…”

Exotic nuclear matter

“…The QPM results have recently applied very successfully in astrophysical investigations [12,23]. The model as used for beta-stable and unstable nuclei is found to provide a nearly perfect description of astrophysical reaction rates, much better than the widely used QRPA approach which, in fact, should be considered as a first order approximation.…”

“…In recent years nuclear density functional theory and nuclear many-body methods -ranging from HFB and (Q)RPA theory to the QPM approach of Soloviev et al -have been used to study systematically ground state properties and multipole response functions of exotic nuclei, especially in the region of the N = 82 and the Z = 50 shell closures, see e.g. [1] and detailed studies are found in [2][3][4][5][6][7][8][9][10][11][12][13][14]. None of those systems can be explored without an adequate reaction theory.…”