The Infrared and Raman Spectra of Powdered and Single-Crystal Barium Chlorate Monohydrate and -deuterate

Abstract

The infrared and Raman spectra of polycrystalline and single-crystal Ba(ClO₃)₂•H₂O and Ba(ClO₃)₂•D₂O have been obtained. The observed bands have been assigned to the various Davydov components of the intramolecular modes and colattice modes. For the water molecule, all of the fundamentals of H₂O, HDO, and D₂O have been located, the anharmonicities of the bending modes have been determined, and those of the stretching modes are essentially the same as for water vapor. The intermolecular coupling is very weak. The effective harmonic force field for the water molecules has been calculated. The stretch–stretch interaction constant is much smaller than for water vapor, reflecting a smaller separation of the asymmetric and symmetric stretching modes. The intermolecular vibrations of the water molecules have been located. For the chlorate ions, in spite of the disorder due to the ³⁷Cl, the spectra can be interpreted in terms of unit cell modes, albeit as a first approximation. The isotope shift of the symmetric Cl—O stretching mode appears to be unusually large. The far-infrared spectra have been tentatively assigned to translational and rotational vibrations involving the Ba²⁺ and ClO₃⁻ ions.