Raman scattering study of interactions of cyanide impurities in KCl under variation of temperature and concentration

The interactions of ${\mathrm{CN}}^{\mathrm{-}}$ impurities in KCl are investigated by Raman light scattering in the spectral region of the ${\mathrm{CN}}^{\mathrm{-}}$ stretching frequency. The low-temperature width and observed motional narrowing of the primary peak assigned to isolated cyanide impurities is attributed to interaction with non-near-neighbor defects in the lattice. A splitting is observed in a spectral feature attributed to ${\mathrm{CN}}^{\mathrm{-}}$ pairs and attributed to a dynamical interaction (Davydov splitting). This suggests a model for nearest-neighbor pairing. The relative positions and intensities of downshifted sidebands are explained by this model.