Editor's Summary

13 September 2007

Positronium molecules

It has been known for many years that an electron and its antiparticle, the positron, can together form a metastable hydrogen-like atom, positronium (Ps). It was predicted that two Ps atoms may combine to form di-positronium (Ps2), but this molecule has not been observed unambiguously: until now. When intense positron bursts are implanted into a thin film of porous silica, Ps2 is created on the internal pore surfaces. Using a more intense positron source, it may be possible to form a Bose–Einstein condensate of Ps2 molecules, which would be of significant fundamental interest and a milestone on the path to produce an annihilation gamma-ray laser.

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LetterThe production of molecular positronium

D. B. Cassidy & A. P. Mills, Jr