Motion and phase changes in molecular solids containing CH3groups: I. Nuclear magnetic resonance in solid 2,2- and 2,3-dimethylbutane

A detailed study of the nuclear magnetic resonance spectra and the proton spin-lattice relaxation times in solid 2,2- and 2,3-dimethylbutane have been made from 20 °K to their melting points. The interpretation of the data is consistent with thermal, x-ray and Raman studies. At low temperatures the spectra are narrower than expected for an effectively rigid lattice, and it is concluded that the tunnelling by the CH 3 rotors narrows the observed spectra. The proton spin-lattice relaxation mechanism is not sensitive to this motion.