Knowledge Bank

The polarized Raman and infrared reflection spectra of molybdate and tungstate compounds of barium and strontium are presented and analyzed. The longitudinal and transverse frequencies of the infrared active phonons were calculated by a Kramers-Kroning analysis of the reflection spectra. A strain induced forbidden mode was observed in the reflection spectra that gives interpretation of the strong shoulder on the $\nu 3$ bands in the absorption spectra of mulled samples. The correlation field splittings of the internal modes were analyzed in terms of dipole-dipole interaction theory. The correlation field splittings of the $\nu 3$ stretching modes were found to be explainable in terms of dipolar coupling, while the splittings of the $\nu 2$ and $\nu 4$ bending modes could not be accounted for in terms of dipolar coupling alone.