RAMAN-STUDY OF A PHASE-TRANSITION IN SOLID TRIFLUOROIODOMETHANE

Raman spectra of solid trifluoroiodomethane are reported for both the lattice and internal mode regions for samples at temperatures between 12 and 130 K. A solid-state phase transition at about 115 K is confirm ed. Above this temperature, the spectra are characteristic of a disord ered or highly anharmonic solid. At low temperatures, the spectra are compatible with an ordered, harmonic molecular crystal with a unit cel l containing at least four molecules. Plausible assignments of all obs erved spectroscopic features are proposed.