Stress‐Induced Dichroism in Tl+‐Doped Potassium Halides

Change of absorption under uniaxial compressive stress has been investigated in KCl: Tl+ and KBr: Tl+ on the A‐band and in KI: TI+ on the A‐ and B‐bands at 77 and 20 °K. A. light modulation method has been applied with a rotating polarizer. The data were analysed by the method of moments and show a red shift of the bands with stress and polarization parallel to the [100] axis and a blue shift of the bands with stress and polarization parallel to the [110] axis. From these data it is concluded that the Jahn‐Teller distortion of the Eg mode of the A‐excited state leads to a compression of the impurity octahedron.