Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso


  • William M. Irvine
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_5238-1



Argonium is the argon hydride cation, ArH+. Argon has three naturally occurring isotopes, with the cosmically most abundant being 36Ar, followed by 38Ar, and then 40Ar. On Earth, in contrast, 40Ar is by far the most abundant isotope, derived primarily from the radioactive decay of 40K. The K-Ar decay is important for geochronology. Argonium is the first noble gas molecule to have been found in space, with both the 36Ar and the 38Ar isotopologs observed by astronomers. Extensive laboratory studies of the rotational spectra and the electric dipole moment have been carried out for both 36ArH+ and 38AH+; AH+ is quite stable, with a dissociation energy of almost 4 eV.


Astronomically, argonium was first reported in the Crab Nebula, the remnant of the supernova observed by Chinese astronomers/astrologers in 1,054 CE (Barlow et al. 2013). The observed 36Ar was presumably produced by explosive nucleosynthesis during the supernova event. Both 36ArH+ and 38AH+...


Dipole Moment Electric Dipole Dissociation Energy Molecular Hydrogen Electric Dipole Moment 
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References and Further Reading

  1. Barlow MJ, Swinyard BM, Owen PJ, Cernicharo J, Gomez HL, Ivison RJ, Krause O, Lim TL, Matsuura M, Miller S, Olofsson G, Polehampton ET (2013) Detection of a noble gas molecular ion, 36ArH+, in the crab nebula. Science 342:1343–1345CrossRefADSGoogle Scholar
  2. Schilke P, Neufeld DA, Müller HSP, Comito C, Bergin EA, Lis DC, Gerin M, Black JH, Wolfire M, Indriolo N, Pearson JC, Menten KM, Winkel B, Sánchez-Monge Á, Möller T, Godard B, Falgarone E (2014) Ubiquitous argonium (ArH+) in the diffuse interstellar medium – a molecular tracer of almost pure atomic gas. Astron Astrophys 566:A29Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Department of AstronomyLederle Graduate Research Tower B 619E, University of MassachusettsAmherstUSA