The Resonance Line of the Iodine Atom and the Optical Dissociation of Iodine Molecules

The resonance line of the iodine atom is most probably that of wave-length 1830.4A, corresponding to a resonance potential of 6.75 volts. Light of that wave-length is absorbed by a cell containing iodine vapor more strongly when it is illuminated by concentrated light from a carbon arc than when it is not so illuminated. The increased absorption is attributed to iodine atoms produced by the illumination, in accord with Franck's theory of optical dissociation.