Optical Absorption ofCl2−Molecule-Ions in Irradiated Potassium Chloride

Pure KCl, KCl-Ag, KCl-Tl, and KCl-Pb, after x-ray irradiation at liquid nitrogen temperature, show identical ${\mathrm{Cl}}_2^{-}$ paramagnetic resonance spectra. The optical absorption of the ${\mathrm{Cl}}_2^{-}$ molecule-ion has been identified and is found to consist of two bands, one at 365 mμ and one at 750 mμ. This identification was made possible by bleaching irradiated samples with polarized light and observing the effects on the optical and also the paramagnetic resonance spectra. It was possible to reorient the ${\mathrm{Cl}}_2^{-}$ molecule-ions such that a large fraction of them were in only one of the six possible $〈110〉$ directions.