Editing Protonium (section)

{{Short description|Bound state of a proton and antiprotron}}
[[File:Structure of Protonium.svg|thumb|An illustration of the protonium atom.]]
{{distinguish|Positronium}}
{{hatnote|For the isotope <sup>1</sup>H and the corresponding hydrated ion, see [[Hydrogen-1|Protium]] and [[Hydronium]].}}

'''Protonium''', also known as '''antiprotonic hydrogen''', is a type of [[exotic atom]] in which a [[proton]] (symbol: p) and an [[antiproton]] (symbol: {{overline|p}}) are bound to each other.<ref>{{cite journal |last=Zurlo |first=N. |display-authors=etal.  |title=Production Of Slow Protonium In Vacuum |journal=[[Hyperfine Interactions]] |volume=172 |issue=1–3 |pages=97–105 |arxiv=0801.3193  |bibcode= 2006HyInt.172...97Z |doi=10.1007/s10751-007-9529-0 |year=2006 |s2cid=119182686 }}</ref>

Since protonium is a [[bound state|bound system]] of a [[particle]] and its corresponding [[antiparticle]], it is an example of a type of [[exotic atom]] called an ''[[onium]]''.

Protonium has a [[Exponential decay#Mean lifetime|mean lifetime]] of approximately 1.0&nbsp;[[Microsecond|μs]] and a binding energy of −0.75&nbsp;[[Electronvolt|keV]].<ref>{{cite journal |last=Abdel-Raouf |first=Mohamed Assad |title=Binding energy of protonium ions |journal=Journal of Physics: Conference Series |volume=194 |issue=7 |doi=10.1088/1742-6596/194/7/072003 |year=2009 |page=072003 |bibcode=2009JPhCS.194g2003A |doi-access=free }}</ref>

Like all onia, protonium is a [[boson]] with all quantum numbers ([[baryon number]], [[flavour quantum number]]s, etc.) and [[electrical charge]] equal to 0.