Cyanate Ion in Alkali Halides: New Vibrational Levels and Interpretation of Localized Lattice Modes

The infrared absorption of alkali halide single crystals containing NCO(-) impurity at concentrations up to about 1 mole % has yielded new information about the internal vibrational levels of the cyanate ion. Satellite lines near nu(3) and its combinations have been shown to arise from neighbor pairs of cyanate ions in the host lattice. Absorptions of the type nu(3)+/-nu(k), where nu(k) is of the order of 80 to 180 cm(-1) and is strongly dependent upon the host lattice, have been observed; and the relation of nu(k) to the impurity-induced localized lattice modes is discussed.