The infrared and Raman spectra of solid CH3F and CD3F: Crystal structure inferences

Abstract

Infrared and Raman spectra are reported for solid CH₃F and CD₃F, and infrared spectra of dilute solid solutions of each substance in the other are also reported, in the region of the internal fundamentals and at temperatures near 80 °K (infrared) and near 130 °K (Raman). The crystal structure, based on the splittings in the spectra, is believed to be centrosymmetric with four molecules in the unit cell, similar to that of methyl bromide and methyl iodide. The possibility of longitudinal optical modes appearing in the Raman spectrum is considered; several reasons lead us to reject this suggestion. Overtones and combinations are assigned, in both infrared and Raman spectra, and shifts between gas and solid phases are discussed.