Peter von Neumann-Cosel

Pair decay width of the Hoyle state and carbon production in stars

The pair decay width of the first excited 0+ state in 12C (the Hoyle state) is deduced from a novel analysis of the world data on inelastic electron scattering covering a wide momentum transfer range, thereby resolving previous discrepancies. The extracted value ?? = (62.3 ? 2.0) ?eV is independently confirmed by new data at low momentum transfers measured at the S-DALINAC and reduces the uncertainty of the literature values by more than a factor of three. A precise knowledge of ?? is mandatory for quantitative studies of some key issues in the modeling of supernovae and of asymptotic giant branch stars, the most likely site of the slow-neutron nucleosynthesis process.

Electron capture radioactive sources for intravascular brachytherapy: a feasibility study

The feasibility of electron capture (EC) radionuclides as an alternative to the β and high-energy γ emitters presently in use for intravascular brachytherapy is investigated. A potential advantage of the low-energy x-ray radiation from EC isotopes may be an enhanced biological effectiveness with respect to the presently applied β nuclides, but at the same time avoiding the shielding problems induced by the large penetrability of high-energy γ rays. A survey considering the most important practical aspects such as dose delivery to the vessel walls in reasonable time spans, absorption properties, possible production of sources with the required specific activities and radiation safety reveals 71 Ge as the most promising candidate.

Comment on “New formulas for the(−2)moment of the photoabsorption cross section,σ−2”

Empirical formulas for the second inverse moment of the photoabsorption cross sections in nuclei are discussed in J. N. Orce, Phys. Rev. C 91, 064602 (2015). In this Comment I point out that the experimental values used are systematically too small in heavy nuclei by about 10% because of the neglection of the E1 strength below the neutron threshold. Furthermore, combining recently deduced values of the polarizability in heavy and total photoabsorption data in light nuclei it is demonstrated that the mass number dependence of \sigma_(-2) is sensitive to the ratio of volume and surface coefficients of the symmetry energy and parameters different to the ones chosen by Orce may be better suited.

Complete electric dipole response in 120Sn and 208Pb and implications for neutron skin and symmetry energy

Polarized proton scattering at energies of a few 100 MeV and very forward angles including 0° has been established as a new tool to extract the complete E1 strength distribution in nuclei for excitation energies between about 5 and 20 MeV. A case study of 208Pb demonstrates excellent agreement with other electromagnetic probes. From the information on the B(E1) strength one can derive the electric dipole dipole polarizability, which is strongly correlated to the neutron skin and to parameters of the symmetry energy. Recently, we have extracted the polarizability of 120Sn with a comparable precision. The combination of both results further constrains the symmetry energy parameters and presents a challenge for mean-field models, since relativistic and many Skyrme parameterizations cannot reproduce both experimental results simultaneously.

RECENT RESULTS FROM PHOTON-INDUCED FISSION EXPERIMENTS AT THE S-DALINAC

Bremsstrahlung with endpoint energies slightly above the fission barrier is produced from stopping an electron beam in a thick copper target. Mass, total kinetic energy (TKE) and angular distribution of the fission fragments were determined by means of the double kinetic energy technique, using a twin Frisch-grid ionization chamber. First results on angular distributions and their correlations with mass and TKE of the fragments as well as an analysis within the fission-mode concept of the multi-modal random neck-rupture model by Brosa et al.[2], are presented [3]. It is shown that the emission angle of the fission fragments can be extracted from an electron drift-time measurement [4] and that the target thickness influences the experimental results [5].

Electric dipole response in 120Sn

In high-resolution (,) experiments under 0° the complete B(E1) strength distribution can be studied in stable nuclei. At the Research Center of Nuclear Physics in Osaka, Japan, the cross sections and observables for the polarization transfer of E1 and M1 excitations in 120Sn were measured for scattering angles Θ = 0° − 4° in an excitation energy range of 5 - 25 MeV. From the present measurement the complete B(E1) strength distribution and the branching ratios of the PDR to the ground state can be extracted. The experimental setup, the principle of backgound subtraction and first results on the E1 strength are presented.

Electric dipole response in Sn-120

In high-resolution (,) experiments under 0° the complete B(E1) strength distribution can be studied in stable nuclei. At the Research Center of Nuclear Physics in Osaka, Japan, the cross sections and observables for the polarization transfer of E1 and M1 excitations in 120Sn were measured for scattering angles Θ = 0° − 4° in an excitation energy range of 5 - 25 MeV. From the present measurement the complete B(E1) strength distribution and the branching ratios of the PDR to the ground state can be extracted. The experimental setup, the principle of backgound subtraction and first results on the E1 strength are presented.