Abstract. Recent research has shown that there are a number of atoms and atomic ions that can bind a positron. The number of atoms known to be capable of binding a positron has expanded enormously in recent years, with Li, He(³S^e), Be, Na, Mg, Ca, Cu, Zn, Sr, Ag and Cd all capable of binding a positron. The structure of these systems is largely determined by the competition between the positron and the nucleus to bind the loosely bound valence electrons. Some systems, such as e⁺Li and e⁺Na, can be best described as a Ps cluster orbiting a charged Li⁺ or Na⁺ core, while others such as e⁺Be consist of a positron orbiting a polarized Be atom. In addition, a number of atoms (Li, C, O, F, Na, Cl, K, Cl, Cu, Br) can bind positronium and a few systems capable of binding two positrons have also been identified. These positron-binding systems decay by electron-positron annihilation with the annihilation rate for e⁺A systems largely determined by the parent atom ionization potential.

Print publication: Issue 13 (14 July 2002)
Received 15 January 2002, in final form 16 May 2002
Published 25 June 2002