Helium dimer

Helium dimer
Names
Other names
dihelium
Identifiers
3D model (JSmol)
ChEBI
48
  • : InChI=1S/He2/c1-2
    Key: GHVQTHCLRQIINU-UHFFFAOYSA-N
  • [He][He]
Properties
He2
Molar mass 8.005204 g·mol−1
Appearance colorless gas
Thermochemistry
1.1×10−5 kcal/mol
Related compounds
Related van der Waals molecules
 LiHe NeHe2 He3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N (what is YN ?)
Infobox references

The helium dimer is a van der Waals molecule with formula He2 consisting of two helium atoms. This chemical is the largest diatomic molecule—a molecule consisting of two atoms bonded together. The bond that holds this dimer together is so weak that it will break if the molecule rotates, or vibrates too much. It can only exist at very low cryogenic temperatures.

Two excited helium atoms can also bond to each other in a form called an excimer. This was discovered from a spectrum of helium that contained bands first seen in 1912. Written as He2* with the * meaning an excited state, it is the first known Rydberg molecule.

Several dihelium ions also exist, having net charges of negative one, positive one, and positive two. Two helium atoms can be confined together without bonding in the cage of a fullerene.

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