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A. Zilges

Publications and source records attributed to A. Zilges.

46 records · Page 3Linked to original sources
arXiv2005

Elastic alpha-scattering of 112Sn and 124Sn at astrophysically relevant energies

The cross sections for the elastic scattering reactions {112,124}Sn(a,a){112,124}Sn at energies above and below the Coulomb barrier are presented and compared to predictions for global alpha-nucleus potentials. The high precision of the new data allows a study of the global alpha-nucleus potentials at both the proton and neutron-rich sides of an isotopic chain. In addition, local alpha-nucleus potentials have been extracted for both nuclei, and used to reproduce elastic scattering data at higher energies. Predictions from the capture cross section of the reaction 112Sn(a,g)116Te at astrophysically relevant energies are presented and compared to experimental data.

astro-ph↗
arXiv2005

Parity assignments in 172,174Yb using polarized photons and the K quantum number in rare earth nuclei

The 100 % polarized photon beam at the High Intensity gamma-ray Source (HIgS) at Duke University has been used to determine the parity of six dipole excitations between 2.9 and 3.6 MeV in the deformed nuclei 172,174 Yb in photon scattering (g,g') experiments. The measured parities are compared with previous assignments based on the K quantum number that had been assigned in Nuclear Resonance Fluorescence (NRF) experiments by using the Alaga rules. A systematic survey of the relation between gamma-decay branching ratios and parity quantum numbers is given for the rare earth nuclei.

nucl-ex↗
arXiv2005

Systematic study of (g,n) reaction rates for Z>=78 isotopes

The (g,n) reaction rates of the isotopes 196,198,204-Hg and 204-Pb have been determined using the photoactivation technique in an energy region relevant for p process nucleosynthesis. The systematic study of the ground-state (g,n) reaction rates on even-even nuclei in the mass region Z>=78 is complemented with these experiments. The data are compared to rates predicted in the framework of two statistical model approaches.

astro-ph↗
arXiv2004

The (n,g) cross sections of short-living s-process branching points

An experimental method to determine the (n,g) cross section of short-living s-process branching points using data of the inverse (g,n) reaction is presented. The method was used to observe the branching point nucleus 95Zr because the elemental abundance patterns corresponding to this branching point cannot be reproduced by full stellar models and a possible error source is the neutron capture cross section of 95Zr. The analysis of the experiment is still under progress, we will outline the current status in this manuscript.

astro-ph↗
arXiv2002

The s-process branching at 185W

The neutron capture cross section of the unstable nucleus 185W has been derived from experimental photoactivation data of the inverse reaction 186W(gamma,n)185W. The new result of sigma = (687 +- 110) mbarn confirms the theoretically predicted neutron capture cross section of 185W of sigma = 700 mbarn at kT = 30 keV. A neutron density in the classical s-process of n_n = (3.8 +0.9 -0.8} * 1e8 cm-3 is derived from the new data for the 185W branching. In a stellar s-process model one finds a significant overproduction of the residual s-only nucleus 186Os.

astro-ph↗
arXiv2001

$^{92}$Mo($α,α$)$^{92}$Mo scattering,the $^{92}$Mo--$α$ optical potential, and the $^{96}$Ru($γ,α$)$^{92}$Mo reaction rate at astrophysically relevant energies

The elastic scattering cross section of$^{92}$Mo($α$,$α$)$^{92}$Mo has been measured at energies of $E_{\rm{c.m.}} \approx$ 13, 16, and 19 MeV in a wide angular range. The real and imaginary parts of the optical potential for the system $^{92}$Mo - $α$ have been derived at energies around and below the Coulomb barrier. The result fits into the systematic behavior of $α$-nucleus folding potentials. The astrophysically relevant $^{96}$Ru($γ$,$α$)$^{92}$Mo reaction rates at $T_9=2.0$ and $T_9=3.0$ could be determined to an accuracy of about 16 % and are compared to previously published theoretical rates.

astro-ph↗
arXiv2001

Measurement of the (gamma,n) reaction rates of the nuclides 190Pt, 192Pt, and 198Pt in the astrophysical gamma-process

The nucleosynthesis of heavy neutron-deficient nuclei in a stellar photon bath at the temperatures relevant for the astrophysical gamma process was investigated. In order to derive (gamma,n) cross sections and reaction rates, the stellar photon bath was simulated by the superposition of several bremsstrahlung spectra with different endpoint energies. As a first test for this method, the (gamma,n) reaction rates of the platinum isotopes 190Pt, 192Pt, and 198Pt were derived. The results are compared to other experimental data and theoretical calculations.

astro-ph↗