NMR relaxation study of methyl groups in solids from low to high temperatures
ABSTRACT The calculation of the correlation functions of complex motion consisting of jumps over the barrier (classical motion) and jumps through the barrier (incoherent tunneling) is presented. The Schrödinger equation has been applied in the calculation of the rate constant of tunneling jumps through the barrier. This rate constant determines directly the temperature at which incoherent tunneling ceases. The calculated spectral densities are applied to analyze the temperature dependencies of the spin-lattice relaxation rate in solids containing a methyl group. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson Part A 27A: 38–53, 2005.