INFRARED-SPECTRA OF SOLID CHLORODIFLUOROMETHANE

Infrared spectra of solid chlorodifluoromethane (CHClF2 or Freon 22) at temperatures between 12 and 105 K are presented and discussed. The evidence for a reversible solid state phase transition at (55 +/- 5) K is described, confirming the results of a previous Raman study. Two metastable phases are also detected. Multiplet structure is observed for all nine internal modes and interpreted in terms of crystal field effects. This confirms that both phases are ordered, with rather large unit cells, and that the transition is of a displacive type. Coincidences with Raman frequencies suggest that both structures are probably non-centrosymmetric. The lattice spectra are compatible with these conclusions and are tentatively assigned on the basis of inertia and intensity arguments.