NMR of protons in gypsum. II. Independent observation of molecular reorientations and molecular diffusion

In this paper the spin-lattice relaxation properties of the four quasi-invariants for the proton spins of water molecules in gypsum, caused by independent and thermally activated flips of the water molecules, are evaluated. A comparison of these predictions with experimental results (in the temperature range between 110 and 400^∘{}K) shows that the 180^∘{} flips are indeed the dominant relaxation mechanism of all four invariants over a wide temperature range, with one exception for intermolecular energy at each end of this range.