Distributions of site-hopping geometries and rates for benzene adsorbed onAg-Y zeolite

Slow jump reorientation dynamics of benzene molecules adsorbed on Ag-Y zeol ite (Si/Al = 2.4) have been investigated using solid-state nuclear magnetic resonance (NMR) spectroscopy. Multidimensional exchange C-13 NMR technique s establish that the benzene jump angle distribution is broad and that mult iple benzene reorientation rates exist for site exchange among different lo cal environments. Modeling of H-2 and C-13 NMR line shapes yields an appare nt activation energy of 34 +/- 2 kJ/mol and a preexponential factor of k(0) = 2 x 10(10) s(-1) (+/- 1/2 decade) for the complicated molecular reorient ation motions underlying benzene site-hopping dynamics in Ag-Y zeolite.