(redirected from Parapositronium)
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A short-lived association of an electron and a positron bound together in a configuration resembling the hydrogen atom.


(Atomic Physics) physics a short-lived entity consisting of a positron and an electron bound together. It decays by annihilation to produce two or three photons
[C20: from positron + -ium]


(ˌpɒz ɪˈtroʊ ni əm)

a short-lived atomic system consisting of a positron and an electron bound together.
[1945; positron + -ium2]
References in periodicals archive ?
This explains why orthopositronium, where the particle (electron and positron) spins are parallel and hence the magnetic component of the electromagnetic interaction is repulsive, has a higher energy state than parapositronium where the particle spins are anti-parallel and the magnetic component of QED is attractive.
There are two kinds of positronium: parapositronium p-Ps, in which the spins of the electron and the positron are oppositely directed so that the total spin is zero, and orthopositronium o-Ps, in which the spins are codirected so that the total spin is one.
T]Ps [arrow right] nothing, because products of decay passed into the mirror Universe can not be detected; (2) the ratio between orthopositronium and parapositronium numbers will decrease from [sup.