An NMR study of the solid phase of trifluoromethane

Nuclear magnetic absorption line shape and spin-lattice relaxation (T1, T1ρ) measurements have been made on the 1H and 19F nuclear species in solid CHF3 over the temperature range 4.2 to 120 K. The dominant motional mechanism has been found to be a threefold reorientation of the molecules with activation energy 4.3±0.2 kcal/mol and pre-exponential Arrhenius factor in the range 4.9×10−17–8.9×10−17 s. An additional low temperature mechanism has been associated with transitions between the librational states of the molecules. The threefold reorientation is discussed in terms of a possible crystal structure, and is also related to the nonexponential relaxation observed in the 1H T1 data.