has performed a set of absolute Fission Product Yield (FPY) measurements. Using monoenergetic neutron at energies between 0.5 and 14.8 MeV, the excitation functions of a number of fission products from 235 U, 238 U and 239 Pu have begun to be mapped out. This work has practical applications for the determination of weapon yields and the rate of burn-up in nuclear reactors, while also providing important insight into the fission process. Combining the use of a dual-fission ionization chamber and-ray spectroscopy, absolute FPYs have been determined for approximately 15 di↵erent fission products. The dual-fission chamber is a back-to-back ionization chamber system with a 'thin' actinide foil in each chamber as a monitor or reference foil. The chamber holds a 'thick' target in the center of the system such that the target and reference foils are of the same actinide isotope. This allows for simple mass scaling between the recorded number of fissions in the individual chambers and the number of fissions in the center thick target, eliminating the need for the knowledge of the absolute fission cross section and its uncertainty. The 'thick' target was removed after activation and-rays counted with well shielded High Purity Germanium (HPGe) detectors for a period of 1.5-2 months.

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 HI γS 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 ± 2.0 µ 2 N , 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 206 skin = 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 205 Pb(n,γ) 206 Pb 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.

The electromagnetic dipole strength below the neutron-separation energy has been studied for the xenon isotopes with mass numbers A = 124, 128, 132, and 134 in nuclear resonance fluorescence experiments using the γELBE bremsstrahlung facility at Helmholtz-Zentrum Dresden-Rossendorf and the HIγS facility at Triangle Universities Nuclear Laboratory Durham. The systematic study gained new information about the influence of the neutron excess as well as of nuclear deformation on the strength in the region of the pygmy dipole resonance. The results are compared with those obtained for the chain of molybdenum isotopes and with predictions of a random-phase approximation in a deformed basis. It turned out that the effect of nuclear deformation plays a minor role compared with the one caused by neutron excess. A global parametrization of the strength in terms of neutron and proton numbers allowed us to derive a formula capable of predicting the summed E1 strengths in the pygmy region for a wide mass range of nuclides. Photon strength functions (PSF) are important inputs for statistical reaction codes applied in network calculations in nuclear astrophysics and in simulations done for nuclear power production and safety. Knowing and understanding the behavior of the PSF in the energy region around and below the neutron threshold is essential for these applications. For the dominating electric dipole (E1) part of the PSF, the RIPL3 compilation of the IAEA [1] offers an overview on various models, which in essence base on the concept of the damped isovector E1 giant dipole resonance (GDR). It is described by one or two Lorentzian functions with parameters fitted to the characteristic resonance structure observed in (γ, n) reactions. For open shell nuclei, which constitute the majority, the nuclear deformation is taken into account. It splits the peak of the GDR [2, 3] and, as a consequence, increases the dipole strength distribution in the region below the neutron-separation energy. Along these lines, a new global description of the PSF was recently presented in Ref.[4], which takes triaxial quadrupole deformation into account and which is called triple Lorentzian model (TLO).Experimental and theoretical studies [5][6][7][8][9], which have been recently reviewed by Savran, Aumann, and Zilges [10] suggest a richer structure of the PSF below the neutron-separation energy than accounted for by the Lorentzian-type models. In this letter we follow the suggestion in the review [10]: "Today the term Pygmy Dipole Resonance (PDR) is frequently used for the low-lying E1 strength and we will follow this notation in this review without implying with this notation any further interpretation of its structure." The rational behind this terminology is that the interpretation of the PDR depends strongly on the theoretical model invoked and present day experiments cannot distinguish between the models. One important aspect of studying the PDR concerns its isospin dependence, which is particularly important for simulating the r-process that d...