For the reaction, Br2(g)+Cl2(g)⇄2BrCl(g), recently used values for the equilibrium constant K° range from 6 to 10. The spread is due to the use (explicit or implicit) of different values for the dissociation energy of BrCl. The most recent assessment of this quantity yielded De=18 247±5 cm−1, from which the equilibrium constant is 8.95±0.5. It should be possible to sharpen the determination of De and K° by observing the predissociation-induced breakoff of fluorescence from low J levels of v=7 in the B state of the Br37Cl isotopomers.

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