SINGLE-CRYSTAL POLARIZED SPECTRA IN THE NEAR-INFRARED REGION - A LOCAL-MODE ANALYSIS OF THE SPECTRA OF CSMNCL3.2X(2)O (X=H,D)

Polarized near-infrared spectra of single crystals of CsMnCl3.2X(2)O ( X = H, D) were recorded at 10 K. Those bands which could be assigned t o O-H or O-D stretch overtones were analyzed using local-mode theory s pecifically adapted for systems having less than C-2v symmetry. Both O -H oscillators form nearly linear hydrogen bonds to neighboring chlori de ions at different distances. As a result, the local-mode harmonic f requency and anharmonicity parameters show characteristic shifts from their gas-phase values. The parameter values cover an unusually narrow range in this crystal, considering the spread in hydrogen-bond distan ces. Assignment of stretch overtone bands to specific oscillators in t he crystal was made by using the polarization behavior expected of loc al modes in the oriented gas model. Several of the overtone bands show combinations with lattice modes or low-energy hydrogen-bond modes in unusual detail.