Photochemical Reaction and Photoconductivity of Additively Colored KCl Crystals at Low Temperature

Abstract

The change in the photoconductivity of KCl crystals containing F centers upon optical bleaching of the F band has been investigated at low temperature. It was shown that the presence of M centers is not responsible for the residue of the photoconductivity in the F band region at low temperature. F′ centers were produced through a tunneling process when F centers were optically excited at low temperature. The quantum yield of the process was dependent on the concentration of F centers and was estimated to be less than 0.06 in a specimen containing 6×10¹⁶ cm⁻³ of F centers. The residual photoconductivity in the F band region at low temperature was found to result not from the absorption of photons in the F band but from the absorption in a band overlapping the F band. The suggested shape and position of the band are given.