Antiprotonic atoms

Antiprotonic atoms, in which an orbiting electron of a normal atom is replaced by an antiproton, are the latest exotic atoms to be discovered. After a short introduction to the essentials of exotic atoms the properties of antiprotonic atoms, their production and detection are discussed. This includes remarks on novel schemes to produce and detect antiprotonic X-rays and to determine the levels of these atoms as well as on the revolutionary progress due to the antiproton source LEAR, from which a major part of the new results in this article are obtained. Very different fields in physics benefit from these studies. They range from studies of atomic cascades, which are more difficult with lighter orbiting particles, to investigations of the p-bar-nucleus interaction bearing on nuclear structure as well as on the elementary p-barp and p-barn interactions. Last but not least the most precise data on the properties of the antiproton itself are derived from antiprotonic X-ray spectra. The study of the fundamental p-barH system discussed at the end can be taken as a good example of recent progress. (author)