Nuclear physics for stellar explosions

点击翻译按钮获取中文摘要

The understanding of the origin of isotopes heavier than those in the iron peak region is one of the most active fields in nuclear astrophysics. This is especially true for the nucleosynthesis in explosive stellar environments where exotic nuclei and their reactions play a crucial role. While experiments at large-scale radioactive-beam facilities like FAIR and FRIB aim to measure key reactions on certain of those exotic nuclei, small accelerator facilities contribute via systematic precision studies on stable isotopes. We will use activation and in-beam techniques with high-resolution HPGe γ detectors and 4π-summing crystals for the latter approach. Both approaches together are important to get a reliable theoretical description of nucleosynthesis.The project is divided into two subprojects: In the first subproject we aim to gain a deeper understanding of low-energy α-particle transmission coefficients for heavy isotopes and their evolution with changing proton-neutron asymmetry. This knowledge is necessary for a description of the synthesis of proton-rich isotopes via the so called p process. In our experiments we will study (α,γ) and (α,n) cross sections on selected isotopes. The second subproject focuses on studies of the γ-strength function in the mass region around A=100 which is an important input for the network calculations on the r process and p process. For this purpose we will measure (p,γ) reaction rates on isotopes around A≈100.The experimental studies in both projects will use the dedicated experimental setups for in-beam and activation studies at the Tandem accelerator of the University of Cologne, the 4π summing array HECTOR at Notre Dame University, and the activation setup at the PTB Braunschweig. The project will be performed in close collaboration with theoreticians in the field.