Untersuchung der Struktur von exotischen Atomkernen mit Lebensdauermessungen angeregter Kernzustände

• Antragsteller: Professor Dr. Alfred Dewald
• Fachliche Zuordnung: Kern- und Elementarteilchenphysik, Quantenmechanik, Relativitätstheorie, Felder
• Förderung: Förderung von 2013 bis 2019
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 236288928

The aim of the project is the investigation of exotic atomic nuclei far from the valley of stability. In particular we want to examine the evolution of collectivity in the close vicinity of nuclear (sub-)shell closures and changes in the shell structure of nuclei with extreme ratios of protons and neutrons. Such phenomena were already found in some exotic nuclei, but overall, data are still sparse and a general picture is missing, especially for neutron rich nuclei around A=60 and A=80 and neutron deficient nuclei around A=180. Notably, data on absolute transition strengths between low-lying states are often not existing. These observables allow for stringent tests of nuclear models and are essential to describe the structure of exotic systems. We want to determine absolute transition strengths from level lifetimes measured with the Recoil Distance Doppler-Shift Method (RDDS) and the Differential Decay Curve Method (DDCM) employing techniques and plunger devices that were developed by our group. Thus we want to analyze data sets recently measured by us on neutron rich 84,86Se and 58,60,62Cr to learn about the topics mentioned above on the evolution of collectivity in exotic nuclei with extreme isospin. Those measurements were done in inverse kinematics including recoil identification. Further, an investigation of neutron deficient A=180 nuclei is foreseen. For this purpose we recently performed experiments on 178,180Pt. The data analysis will be done within this project. In addition, measurements on 178W and on 178Hg near the proton-dripline are intended. These new data together with existing data sets on nuclei around A=180 will help to achieve a deeper insight in a region of rapid changing nuclear structures. In case of 178Hg our focus is on the shape coexistence that was investigated in heavier mercury and lead isotopes in great detail. We also plan to further develop the existing plunger devices built by our group to adapt these devices in an optimal way to new conditions and modified experimental set-ups. A development of the software used to analyze lifetime data is foreseen, too. To precisely determine lifetimes in experiments in inverse kinematics with high recoil velocities of several ten percent of the speed of light the knowledge of the Gamma-ray line shape is needed in some cases. Therefore, we propose to perform detailed GEANT4 simulations taking into account significant effects that have to be considered, like detector resolution and efficiency, Doppler effects and slowing down effects of the excited recoils in thick targets and degraders.

• DFG-Verfahren: Sachbeihilfen
• Beteiligte Person: Dr. Christoph Fransen