RAMAN AND INFRARED STUDIES OF LITHIUM AND CESIUM CARBONATES

Raman spectra have been obtained for solid lithium and cesium carbonate over a wide range of temperatures. The results are consistent with the crystal structures, C2/c for lithium carbonate, and P2(1)/c for cesium carbonate. No phase transitions were detected for the solids over the temperature range from 77 K to the melting points. The difference in the crystal structures results in significantly different correlation-field-splitting effects in the out-of-plane bending mode, nu-2 of the carbonate ion. The stacking of the planar carbonate ions in lithium carbonate results in very large correlation field splitting in the nu-2 and 2-nu-2 regions. An anomalously small shift of the peak position of the nu-2 band of (CO32-)-C-13 relative to the main band of (CO32-)-C-12 for Li2CO3 has also been explained. The (CO32-)-C-13 ion in natural abundance can be treated as a partially decoupled guest impurity in the lattice of the strongly coupled (CO32-)-C-12