0000000000200919
AUTHOR
Joachim Görres
rp-process nucleosynthesis at extreme temperature and density conditions
We present nuclear reaction network calculations to investigate the influence of nuclear structure on the rp-process between Ge and Sn in various scenarios. Due to the lack of experimental data for neutron-deficient nuclei in this region, we discuss currently available model predictions for nuclear masses and deformations as well as methods of calculating reaction rates (Hauser-Feshbach) and beta-decay rates (QRPA and shell model). In addition, we apply a valence nucleon (NpNn) correlation scheme for the prediction of masses and deformations. We also describe the calculations of 2p-capture reactions, which had not been considered before in this mass region. We find that in X-ray bursts 2p-c…
The astrophysical implications of low-energy resonances in 22Ne + α
Abstract The 22 Ne( 6 Li, d) α-transfer reaction has been used to search for α-unbound levels in 26 Mg of importance for resonant α-capture on 22 Ne in stellar helium burning. To determine the resonance strengths of the observed states the 22 Ne(α, n) 25 Mg reaction was investigated in the energy range between 600 and 900 keV. One resonance was identified and its strength determined. The astrophysical implications of the present results are discussed.
Neutron transmission measurements at nELBE
International Conference on Nuclear Data for Science and Technology, ND 2019, Bejing, China, 19 May 2019 - 24 May 2019; The European physical journal / Web of Conferences 239, 01006 (2020). doi:10.1051/epjconf/202023901006
Study of the β-delayed neutron decay of 17C and 18C
Abstract The β-delayed neutron decays of 17C and 18C have been studied using a time-of-flight array with a high detection efficiency. The 17C and 18C ions were produced by fragmentation of an E A = 69 MeV 22Ne beam. Transitions to several neutron unbound states have been observed for the first time for both decays with total branching ratios of (10.8 ± 2.2)% and (21.4 ± 4.4)%. Half-lives of 193 ± 6 ms and 92 ± 2 ms were found for 17C and 18C, respectively. The results are compared with previous measurements of the β-decays and with shell-model calculations.
Nuclear physics far from stability and explosive nucleosynthesis processes
In this paper, we discuss the astrophysically relevant nuclear-physics input for a selected set of explosive nucleosynthesis scenarios leading to rapid protonand neutron-capture processes. Observables (like,e.g., luminosity curves or abundance distributions) witness the interplay between nuclear-structure aspects far from β-stability and the appropriate astrophysical environments, and can give guidance to and constraints on stellar conditions and/or key features of reaction and decay data for radioactive isotopes.
The endpoint of the rp-process
Abstract The endpoint of rp-process nucleosynthesis in X-ray bursts determines the fuel consumption, the energy generation, and the abundance pattern of the produced nuclei. To investigate the time structure of rp-process nucleosynthesis, we used a nuclear reaction network including nuclei from H to Sn. We found that if 2p-capture reactions are included, the synthesis of nuclei heavier than Kr proceeds faster than previously thought. Therefore, in most X-ray bursts large amounts of nuclei in the A=80–100 region are expected to be produced. With an escape factor of about 1%, X-ray bursts could account for the large observed solar system abundances of the light p-nuclei like 92 Mo and 96 Ru t…
Reaction Rates in the RP-Process and Nucleosynthesis in Novae
Nuclear structure information available on proton rich unstable nuclei were used to evaluate thermonuclear reaction rates in the rp-process in explosive hydrogen burning. These rates were applied in a systematic analysis for a variety of temperature conditions, appropriate to nova explosions, to study nucleosynthesis for isotopes of Ne Na Mg Al Si. The results are discussed in comparison with recent observations of elemental abundances in nova ejecta.
The neutron long counter NERO for studies of neutron emission in the r-process
Abstract The neutron long counter NERO was built at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, for measuring β -delayed neutron-emission probabilities. The detector was designed to work in conjunction with a β -delay implantation station, so that β decays and β -delayed neutrons emitted from implanted nuclei can be measured simultaneously. The high efficiency of about 40%, for the range of energies of interest, along with the small background, are crucial for measuring β -delayed neutron emission branchings for neutron-rich r-process nuclei produced as low intensity fragmentation beams in in-flight separator facilities.