2013/08/30 by Elena Litvinova, Peter Ring, Victor Tselyaev · 1 citation
Physics and Astronomy · #nucl-ex #nucl-th
paper · pdf · doi:10.1103/physrevc.88.044320
published as Phys. Rev. C 88, 044320 (2013) · 12 pages, 8 figures, submitted to Phys. Rev. C, corrected typos
arxiv created 2013/08/30 · arxiv updated 2015/06/16
A two-phonon version of the relativistic quasiparticle time blocking approximation introduces as a new class of many-body models for nuclear structure calculations based on the covariant energy density functional. As a fully consistent extension of the relativistic quasiparticle random phase approximation, the relativistic two-phonon model implies fragmentation of nuclear states over two-quasiparticle and two-phonon configurations coupled to each other. In particular, we show how the lowest two-phonon 1- state, identified as a member of the [2+⊗ 3-] quintuplet, emerges from the coherent two-quasiparticle pygmy dipole mode in vibrational nuclei. The inclusion of the two-phonon configurations into the model space allows a quantitative description of the positions and the reduced transition probabilities of the lowest 1- states in tin isotopes 112,116,120,124Sn as well as the low-energy fraction of the dipole strength below the giant dipole resonance without any adjustment procedures. The model is applied to the low-lying dipole strength in neutron-rich 68,70,72Ni isotopes. Recent experimental data for 68Ni are reproduced fairly well.