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.
KeywordsDipole Moment Electric Dipole Dissociation Energy Molecular Hydrogen Electric Dipole Moment
References and Further Reading
- 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