Absorption Spectra of the Quenched Potassium Iodide Crystal

The absorption spectra of potassium iodide crystals quenched from high temperatures have been investigated. Two absorption bands are observed: 5.21 eV and 4.71 eV at liquid nitrogen temperature, and 5.23 eV and 4.71 eV at liquid helium temperature. An emission band excited into the 5.23 eV absorption band appears around 2.38 eV, and another excited into the 4.71 eV band appears at 3.14 eV at liquid helium temperature. From the absorption, emission, and decay times at each emission peak, it is concluded that the absorption band at 5.21 eV is due to the α-centers, and the other is due to Cu⁺ ions. It should be noted that the α-centers formed in the quenched crystals are very stable compared with those formed by F-center bleaching.