sup 13 C NMR Study of CO Surface Diffusion and Site Exchange

Narrow bandwidth radiofrequency pulses are used to label the sup 13 C nuclear magnetic dipoles of CO adsorbed in specific sites at specific orientations on Rh particles and the evolution of the labeled system is monitored by NMR spectroscopy. The results suggest surface diffusion on multi-faceted particles with an activation energy of 7 + sub _ kcal/mole. Hetero-site exchange is detected by selective labeling of linearly-bonded CO, exclusive of nearest-neighbor bridge-bonded CO.