Publications [#328276] of Werner Tornow

Papers Published
  1. Tonchev, AP; Tsoneva, N; Bhatia, C; Arnold, CW; Goriely, S; Hammond, SL; Kelley, JH; Kwan, E; Lenske, H; Piekarewicz, J; Raut, R; Rusev, G; Shizuma, T; Tornow, W, Pygmy and core polarization dipole modes in 206 Pb: Connecting nuclear structure to stellar nucleosynthesis, Physics Letters B, vol. 773 (October, 2017), pp. 20-25 [doi] .

    Abstract:
    © 2017 A high-resolution study of the electromagnetic response of 206 Pb below the neutron separation energy is performed using a γ→,γ ′ ) experiment at the HIγ→S facility. Nuclear resonance fluorescence with 100% linearly polarized photon beams is used to measure spins, parities, branching ratios, and decay widths of excited states in 206 Pb from 4.9 to 8.1 MeV. The extracted ΣB(E1)↑ and ΣB(M1)↑ values for the total electric and magnetic dipole strength below the neutron separation energy are 0.9±0.2 e 2 fm 2 and 8.3±2.0μ N 2 , respectively. These measurements are found to be in very good agreement with the predictions from an energy-density functional (EDF) plus quasiparticle phonon model (QPM). Such a detailed theoretical analysis allows to separate the pygmy dipole resonance from both the tail of the giant dipole resonance and multi-phonon excitations. Combined with earlier photonuclear experiments above the neutron separation energy, one extracts a value for the electric dipole polarizability of 206 Pb of α D =122±10 mb/MeV. When compared to predictions from both the EDF+QPM and accurately calibrated relativistic EDFs, one deduces a range for the neutron-skin thickness of R skin 206 =0.12–0.19 fm and a corresponding range for the slope of the symmetry energy of L=48–60 MeV. This newly obtained information is also used to estimate the Maxwellian-averaged radiative cross section Pb205(n,γ)Pb206 at 30 keV to be σ=130±25 mb. The astrophysical impact of this measurement—on both the s-process in stellar nucleosynthesis and on the equation of state of neutron-rich matter—is discussed.