Electrolytic reduction of Tl+ ions in KCl crystals

Abstract Electrolytic coloration has been made for KCl crystals doped with Tl + ions and doped with Tl + and Ca 2+ ions. Intensity decrease of the Tl + absorption bands is observed in the two colored crystals, while several new absorption and emission bands are observed. They are attributed to Tl − ions which were converted from Tl + ions by electron injection during electrolytic coloration. Different absorption and emission bands are observed for KCl:Tl and KCl:Tl + Ca crystals. Sharp absorption band appears at 285 nm in the colored KCl:Tl and at 400 and 503 nm in the colored KCl:Tl + Ca. Infrared emission bands are observed at 1470, 1600 and 2185 nm in colored KCl:Tl, while at 1630 and 1900 nm in colored KCl:Tl + Ca. It is suggested that the absorption and emission bands in KCl:Tl + Ca are due to Tl − ions perturbed by Ca 2+ or vacancy at the nearest neighbor.