Bulg. J. Phys. vol.46 no.4 (2019), pp. 395-404



Electromagnetic Transitions and Branching Ratios as a Tool for Investigating the Fine Structure of Nuclear Excitations

N. Tsoneva
Extreme Light Infrastructure (ELI-NP), Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), Str. Reactorului No. 30, 077125 Bucharest-Măgurele, Romania
Abstract. The electromagnetic multipole response of atomic nuclei at extreme isospin is investigated by energy-density functional (EDF) and three-phonon quasiparticle-phonon model (QPM) theory with special emphasis on electric and magnetic dipole and quadrupole excitations below the neutron threshold. Of special interest is the dipole photoabsorption cross-section of 206Pb. From theoretical and experimental studies of this nucleus additional low-energy dipole strength associated with pygmy dipole resonance is found. Furthermore, a stringent comparison of the EDF+QPM theory with recent measurements of lifetimes and branching ratios of 2+ states in 112,114,124Sn hints at the occurrence of a low-energy quadrupole mode of unique character which could be interpreted as pygmy quadrupole resonance.

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