Precision Experiments with Exotic Atoms and Relativistic Exotic Nuclei at GSI

Precision experiments with secondary beams of exotic nuclei separated in flight require special experimental methods to compensate for the inevitable large phase space volume which is populated in the production reaction. In this contribution several key experiments are presented where the projectile fragment separator FRS has been used as a high resolution magnetic spectrometer to perform precise momentum measurements. Progress of mass and lifetime measurements with stored fragments demonstrates the research potential of the unique combination of the FRS and the storage-cooler ring ESR. Pioneer experiments have also been performed with heavy exotic atoms. The spectroscopy of deeply bound pionic states in various lead and tin isotopes has been done with precise momentum measurements at the FRS. The investigations of the in-medium mass modification of pions inside nuclear matter can be widely extended with the corresponding reaction in reverse kinematics with stored radioactive beams.