Microscopic Structure of the Low-Energy Electric Dipole Response of Sn-120

The microscopic structure of the low-energy electric dipole response, commonly denoted as pygmy dipole resonance (PDR), was studied for Sn-120 in a Sn-119(d, p gamma)Sn-120 experiment. Unprecedented access to the single-particle structure of excited 1(-) states below and around the neutron-separation threshold was obtained by comparing experimental data to predictions from a novel theoretical approach. The novel approach combines detailed structure input from energy-density functional plus quasiparticle-phonon model theory with reaction theory to obtain a consistent description of both the structure and reaction aspects of the process. The presented results show that the understanding of one-particle-one-hole structures of the 1(-) states in the PDR region is crucial to reliably predict properties of the PDR and its contribution to nucleosynthesis processes.