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Research group Prof. Dr. Alfred Dewald

Research topics

One focus of our research group is the  analysis of nuclear structure using the methods of gamma-ray spectroscopy. In particular, we use lifetime measurements of excited nuclear states to determine reduced electromagnetic transition probabilities. In addition to the level energies, these are important experimental quantities that can be used to obtain information about the nuclear structure. In general, the atomic nuclei to be investigated are generated by means of selected nuclear reactions at accelerator plants and the level life is measured by Doppler shift methods. To test the underlying nuclear structure, the measured values ​​are compared with model predictions. The models used are on the one hand phenomenological collective models such as e.g. the interacting boson approximation (IBA) or various geometric models (symmetric or triaxial rotor or the vibrational model). For atomic nuclei near shell closures, so-called large-scale shell-model calculations are also used to describe the experimental transition probabilities. In these cases, only a few nucleons are involved in the nuclear excitation, while in collective excitations almost all nucleons in the valence space are involved.

One of the questions in this context is, for example, how does collectivity develop in regions that are far from the valley of stability? Other current questions are, for example: Which nuclei establish different shapes at the same time, when does shape coexistence occur, or when are there shape-phase transitions?

Furthermore, we are active in the accelerator mass spectrometry, where we deal with the actual measurement of isotope ratios as well as with the detector and method development.

The research group currently deals with the following main research areas:

  • Lifetime measurements of excited nuclear states using Doppler shift methods
  • Lifetime measurements of long-lived nuclides
  • Developments of Plunger devices
  • Material analysis with ion beams (RBS, PIXE, PIGE, NRF)
  • Surface analysis using XRF
  • Accelerator mass spectrometry
  • Detector development for ion beam analysis
  • Ion source improvement
  • Ion optics
  • Programming of control software

In each area we offer bachelor, master or doctoral theses as well as final theses for teachers. This includes apparatus developments, experiments at different accelerator systems, as well as theoretical work on this topic.