Theory for the Non-Devonshire Lines Observed in the Hydroxyl-Ion-Doped Alkali Halide Matrices

Abstract

The isotope effect of the non-Devonshire lines can be well understood if one takes the origin of these as transitions corresponding to the quantized translational motion of the impurity in the matrix cage and considers the various perturbing mechanisms. The present model in which rotation-translation coupling and coupling through the anisotropic part of crystalline field are considered as the chief perturbing mechanisms proves to be good in explaining the isotope effect of the near-infrared lines in the KCl and KBr matrices. It provides a good explanation of the multiplet line structure observed in the KCl-O${\mathrm{H}}^{-}$ system and absence of such a structure in the KCl-O${\mathrm{D}}^{-}$ system. The more complex case of the NaCl matrix is also explained in a satisfactory way. There has not been an attempt to explain the RbCl-O${\mathrm{H}}^{-}$ system because of the lack of sufficient experimental data.