Near and far infrared vibrational absorption ofH ⁻ _i andD ⁻ _i centres in KBr

Abstract

Near infrared absorption measurements by Gross and Bron led to the suggestion that the threefold degeneracy of the localized vibration ofH ⁻ _i andD ⁻ _i centres in KI is completely lifted in KBr. Using thermal annealing procedures,H ⁻ _i -D ⁻ _i substitution and far infrared techniques we found that the lines at 794, 840, and 896 cm⁻¹ cannot be interpreted as a splitting of the main line. Only the 794 cm⁻¹ line can be correlated with the direct excitation of theH ⁻ _i oscillator. The absence of any splitting in this line (its halfwidth at 9 °K is only 1.5 cm⁻¹) indicates that also in KBrH ⁻ _i centres have at most only slightly perturbedT _d symmetry.