page_title: Diargon
section_title: Theory
hierarchical_section_title: Diargon / Theory
caption_attribution_description: Interaction energy of argon dimer. Empirical potential taken from R. A. Aziz, J. Chem. Phys., vol. 99, 4518 (1993).
context_page_description: Diargon or the argon dimer is a molecule containing two argon atoms. Normally, this is only very weakly bound together by van der Waals forces. However, in an excited state, or ionised state, the two atoms can be more tightly bound together, with significant spectral features. At cryogenic temperatures, argon gas can have a few percent of diargon molecules.
context_section_description: Two argon atoms are attracted together by van der Waals forces when far from each other. When they are close, electrostatic forces repel them. There is a balance point where the van der Waals force matches the opposing repelling force, where energy is at a minimum, represented as the trough in the graph of interaction energy versus distance. This distance is the ground state of the unexcited argon dimer. In a vibrating molecule, the distance between the atoms bounces backwards and forwards from one side of the trough to the other. Faster vibrations will force the state up to higher levels in the energy trough.  If the vibration is two much the molecule will break up. In a rotating molecule, the centrifugal force drags the atoms apart, but can still be overcome by the attractive force. But if the rotation is too much the atoms break apart.
caption: Interaction energy of argon dimer
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