Quasi-Stable Exotic Atoms/Nuclei as Resonance States

Abstract

A review is made of recent theoretical and experimental studies concerning exotic atoms and nuclei with anomalous quasi-stabilities, which are characterized as special types of resonance states embedded in the continuum. They are i) metastable antiprotonic helium atom-molecules pHe+, ii) deeplybound π− states in heavy nuclei and 3) theoretically proposed nuclear K bound states. The narrow decay widths make it possible to perform various highresolution experiments, which yield rich information on the fundamental properties of the antiproton, three-body atomic structure, QED, the pion-nucleus interaction, and the kaon-nucleus interaction.