Joint Nuclear Astrophysics Seminar

The precise knowledge of nuclear response functions plays a key role in the determination of photonuclear reactions cross sections which are of importance for the nucleosynthesis of heavier elements. In this connection information on low-energy excitations located around the neutron threshold is needed.
Recently, new low-energy modes called pygmy resonances which reveal new aspects on the isospin dynamics of the nucleus have been observed. Their distinct feature is the close connection to nuclear skin oscillations which become visible in transition densities and currents.
Here, we present our theoretical approach based on density functional theory and microscopic multi-phonon model which is applied for investigations of pygmy resonances and higher-lying excitations with different multipolarities in stable and exotic nuclei. The possible relation of low-energy modes to the properties of neutron or proton skins is systematically investigated for isotonic and isotopic chains.
The fine structure of nuclear electric and magnetic response functions is analyzed in comparison to experimental data. The relevance to nuclear astrophysics is discussed.

The atomic mass is a fundamental property and links directly and uniquely the binding energy to all effective forces that hold the atom together. In fact, the Nobel Prize awarded Nuclear Shell model was developed only after mass measurements indicated ‘magic’ behavior, which could not be explained with the existing theories at the time. Today, mass measurements are possible at far more isotopes and much more exotic isotopes can be accessed. Moreover, atomic masses are important parameters in nuclear astrophysics, for example for production paths of the chemical elements in stellar object. However, for the measurements, rare short-lived isotopes are required.
At present, one of the premier facilities for rare isotopes is the ISAC accelerator complex at TRIUMF, Vancouver, Canada.
The TITAN (TRIUMF’s Ion Trap for Atomic and Nuclear science) was developed to carry out mass measurements of very short-lived isotopes but maintaining high precision and accuracy. The measurement is carried out using a Penning ion trap, and storing one or a few ions in the trap for the experiment. In this way, some of the most exotic isotopes at any rare beam facility have been measured, and a world record in shortest half-life was achieved. I will give an overview of the TITAN program and how it links to answering some of the big questions in science, and present some resent research highlights.