December 2004

Sodium Chloride

The observation of NaCl was reported in the circumstellar envelope (CSE) of carbon star IRC +10216 in 1987 by Cernicharo & Guélin. Six radio lines were reported. A single line for the mass 37 isotope of Cl was also discerned in the spectrum. NaCl has only been detected in one other source, the CSE of CRL 2688, the Egg Nebula. A number of other small metal-bearing species have been observed in IRC +10216, including AlCl, KCl, AlF, NaCN, MgNC, MgCN, AlNC, FeCN, HMgNC, and others.

Diatomic NaCl has different properties than larger quantities of sodium chloride. It has somewhat more covalent character and thus a smaller dipole moment than if the charge transfer were more complete, as it is in crystalline NaCl.

UPDATE 2023 - Diatomic NaCl has also been detected toward Orion source 1 and IRAS 16547-4247.

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