1H and 2H NMR relaxation in hydrogen-bonded solids due to a complex motion: classical jumps over a barrier and incoherent tunneling.

Equations for the temperature dependence of proton and deuteron spin-lattice relaxation rates and second moments due to a complex motion consisting of classical jumps over a potential barrier and quantum mechanical tunneling through the barrier have been derived. Asymmetric double and triple potential wells are considered. These equations have been employed to analyze proton spin-lattice relaxation data for solid naphthazarin in the laboratory and rotating frames as a function of temperature. It is shown that tunneling plays an important role in the proton transfer dynamics of this compound.