Research group

Prof. Dr. Kathrin Wimmer

In our research group, we investigate the structure of atomic nuclei. A comprehensive understanding requires a combination of experiments at accelerator facilities, including testing new detector systems, simulation studies, and the development of new data acquisition systems and analysis methods. To this end, we not only work on our 10 MV Tandem accelerator, but also collaborate closely with researchers at major international facilities.

Welcome to our research group!

Atomic nuclei are a unique dual quantum liquid consisting of two types of fermions, protons and neutrons. Nuclei are relevant at many length and time scales in the Universe, from the size of a proton (∼10^-15 m) to the size of a neutron star (∼10³ m), and from just after the Big Bang (∼10^-6 s) to the age of the Universe (13.8 x 10⁹ years). Depending on the number of protons and neutrons composing it, the nucleus can have vastly different properties. We are interested in the nuclear collectivity, i.e. how many nucleons participate in excitations. The evolution of collectivity in exotic atomic nuclei is deeply linked with shell evolution and magic numbers. Nuclei with extreme proton to neutron ratios have been explored in the recent years and the disappearance of classic shell closures is always associated with deformation and collective motion. A quantitative measure of the nuclear collectivity is the B(E2), shown here are the known data for the first quadrupole excitation of even-even nuclei [1]. This property maps out the nuclear landscape and shows the regions of nuclear deformation, shell and shape changes, and their deep connection to the magic numbers. Magic and doubly magic nuclei are dominated by single-particle behavior, B(E2) values only amount to a few Weisskopf units (a measure for how many nucleons participate in the excitation). Very collective nuclei have B(E2) values up to several hundred W.u. and the simple interpretation indicates that many nucleons participate in the excitation.

[1] K. Wimmer and P. Doornenbal, "Evolution of collectivity and magic numbers in exotic nuclei", Prog. Part. Nucl. Phys. (to be published)