Infrared Absorption and Local Symmetry of WO‐ and MoO Impurity Ions in KI and CsI Crystals

Abstract

AbstractIn the temperature range 120 to 800 °K and frequency range 1000 to 300 cm−1 a study has been made of the infrared absorption spectra of the impurity anions WO‐and MoO‐in KI and CsI single crystals. It is shown that W and MOO form neutral complexes W · M2+ and MoO · M2+ in KI lattice with cations M2+ (Ca2+, Sr2+, Ba2+) similar to the complexes SO · M2+, CrO · M2+ and SeO · M2+ observed earlier in the f.c.c. lattices. Here a lowering of the local symmetry to C2v of the impurity tetrahedrons results in the appearance of triplets in their vibration regions v3(A2) and v4(F2). The fine structure in the infrared spectrum of MoO · M2+ + KI was interpreted to be isotopic. A local symmetry of the impurity WO and MoO in CsI lattice was not identified unequivocally from the IR absorption spectra. The latter have doublet and quartet structure in the vibration regions v1(A1) and v3(F2), respectively, and depend on the impurity tetrahedrons and M2+ cation concentration. One, probably, should assume the interstitial formation of impurities into b.c.c. lattice of CsI which results in the existence of complex anion‐cation neutral complexes of different kinds.