Laser and decay spectroscopy of neutron-deficient radioactive nuclei in the lead region (Z=82).

The fundamental interactions that are important to explain the properties of an atom are the electromagnetic force, that keep the electrons circling around the atomic nucleus, the weak force, that is responsible for nuclear beta decay which represents an important form of radioactivity, and the strong force, that keeps the protons and neutrons (also called nucleons) together in the nucleus. The electromagnetic force is well known, but the strong- and weak forces are still poorly known. For example calculations that start from basic principles can only predict the properties of the atomic nucleus to a reasonable degree of accuracy up to atoms with twelve nucleons. While atoms with up to three hundred nucleons exist. This proposal aims to learn more about the strong force in these heavier nuclei in order to improve our knowledge of the strong force. This is not only important for our understanding of these fundamental forces in nature, but also for solving questions such as how were the chemical elements made in the universe or what makes the stars shine? Recently it has been realized that some of the hidden secrets of the atomic nucleus might be discovered by studying atoms with an unusual ratio between the number of protons and neutrons. Unfortunately, these atoms are not available on earth as they are radioactive and disappear pretty soon after they have been produced. We have developed a technique to produce these radioactive atoms of interest, to shape them into a radioactive ion beam and to produce point-like and pure sources, surrounded by detectors. The radiation that is emitted in this process gives direct information on the properties of the atomic nucleus. These can in turn be used to fine tune our models and uncover hidden aspects of the strong force. But the production process itself can also reveal important information on the strong force and on the atomic structure of these heavy elements as we use laser light to ionize the atoms of interest. This ultra-sensitive method could also be of interest for the production of medical radio-isotopes of for trace detection. The  experiments are performed at the radioactive ion beam facility ISOLDE at CERN where a new project to substantially improve the intensity and quality of the beams and to accelerate radioactive ion beams to even higher energies (called HIE-ISOLDE) is now in full realization.