Temperature Dependence of Half‐Widths and Integral Absorptions of the Impurity Polyatomic Ion Vibration Bands in Alkali‐Halide Crystals

A quantitative study has been made of the temperature dependence of the half‐widths Avlp and integral optical densities A of the vibration bands v2 and v3 of the impurity anion NCO− in CsI crystals, of the vibrations v1 and v2 of NCS− in CsI, of components of the v3 triplet of the complex SO . Ba2+ in KCI (in the temperature range 100 to 500 °K); and of the vibrations v2 and vg of the anion NO in CsI (in the temperature range 100 to 700 °K). It is shown that the integral absorption remains practically constant for all the bands over the whole temperature range while the half‐widths increase sharply with increasing T. In the representation Δvl/2(T) = Δv1/2(0) + α Tn at rather high T (T > 300 °K) the effective ñ for different bands are calculated with the purpose of determining a preferable mechanism of anharmonic interaction of corresponding intramolecular vibrations (local vibrations in the crystal‐matrix) with lattice phonons. The results obtained agree with existing theoretical views of the role of dissociation and modulation mechanisms of the local vibration band temperature broadening.