Positronium is an exotic atom-like system composed of an electron and its antiparticle, a positron. The electron carries a negative electric charge, while the positron has a positive electric charge. This unique pairing occurs because of the attraction between the two opposite charges, allowing them to bind together.
Articles by others on the same topic
Positronium is the electromagnetic bound state of an electron and a Positron. Their equal masses give reduced mass , half the hydrogenic Rydberg binding scale and approximately twice the electron-proton separation of hydrogen. Its spin singlet and triplet differ in hyperfine energy; annihilation also affects their physical lifetimes and splitting.