Review of experimental and theoretical research on positronium ions and molecules

• Published in: The European physical journal. D, Atomic, molecular, and optical physics Atomic, molecular, and optical physics, 2021-06, Vol.75 (6), Article 188
• Main Authors: Emami-Razavi, Mohsen, Darewych, Jurij W.
• Format: Article
• Language: English
• Subjects: Applications of Nonlinear Dynamics and Chaos Theory; Atomic; Molecular; Negative ions; Optical and Plasma Physics; Physical Chemistry; Physics; Physics and Astronomy; Positronium; Quantum electrodynamics; Quantum Information Technology; Quantum Physics; Spectroscopy/Spectrometry; Spintronics; Topical Review - Atomic Physics
• ISSN: 1434-6060; 1434-6079
• DOI: 10.1140/epjd/s10053-021-00187-4

 In this review we discuss the status of the research for the three-body positronium negative ion ( Ps - , e - e + e - ) and the four-body positronium molecule ( Ps 2 , e - e + e - e + ) from both theoretical and experimental points of view. Experimental results are included to compare with theoretical predictions. J. A. Wheeler, during the 1940s, proved that Ps - has a stable bound state and he also speculated that larger systems such as Ps 2 can exist. There have been several theoretical works starting from the 1940s about the properties of Ps - and Ps 2 . However, experimental observation of such exotic systems proved to be challenging. Thus, Ps - was first observed in 1981 and Ps 2 was only seen in 2007. During recent decades, there have been major advances in determining the properties of the positronium negative ion and the positronium molecule. These studies shed light on the properties of such exotic systems and allow us to better understand and test the theory of quantum electrodynamics (QED). Graphic abstract