A Study about the Optical Absorption Spectra of KC1:hg' BY M. MORENO Baranov e t al. / I / have recently reporled strong evidencw about the formation of Fig+ at cationic positions in KCl c r y s t a l s doped with HgC12 and subjected to X-ray irradiation. The correlation between the ESR and optical absorption (OA)data clearly indicates that three OA bands peaked at 4.30, 4.59, and 5.12 eV are due to Hg+ /l/. Up to now, however, no assignment of such bands has bpen