The19F magnetic resonance absorption of CF4and SF6in their clathrate hydrates

The second moments of 19F nuclear magnetic resonance lines of CF4 and SF6 in their respective clathrate hydrates indicate that these molecules are but little restricted by the walls of the clathrate cavities, and re-orient freely about chosen axes of symmetry at low temperatures and randomly at high temperatures. Above 150°k, we infer from our results that there occurs a limited isotropic translation, or ‘rattling’ movement of an SF6 guest molecule up to a distance of about 0·5 å from the centre of the clathration volume.