Structures of Absorption Bands in Alkali Halide Crystals Containing Tl+-Like Ions under High Pressure

Absorption spectra of NaCl, KCl, KBr and KI crystals doped with In + or Sn ++ have been studied under high pressure. In the case of In + , the splitting energy of the A band and that of the C band become larger as pressure increases. The separation between the center of the A band and that of the C band remains almost constant within the applied pressure in contrast to the increase of the separation between the centers of the A band and the B band. In the case of Sn ++ , the splitting energy of the A band and that of the C band remain constant. The B and C bands hardly show any shift. The pressure dependence of the splitting energies of these bands is discussed with the Toyozawa-Inoue's theory based on the dynamical Jahn-Teller effect.