Tunneling through High Periodic Barriers. II. Application to Nuclear Magnetic Resonance in Solids

Abstract

Analytic formulas derived in an earlier paper for the frequency of tunneling through high periodic barriers are here used to derive from nuclear magnetic resonance data in solids the heights of the potential barriers hindering the rotational motion of molecules. The rotations of CH3 groups, NH3+ groups, benzene, NH2 groups and water molecules of crystallization are considered. The use of the barrier heights in correcting for the effect of torsional vibrations of molecules on molecular dimensions obtained from nuclear magnetic resonance data is illustrated. A possible explanation of an isotropic part of the splitting of the proton resonance in Li2SO4·H2O, reported earlier by Pake, is presented. Comments are made on the relative magnitudes of the barrier heights in the different molecules considered.