Narrow-bandwidth radio-frequency pulses were used to label the 13C nuclear magnetic dipoles of CO molecules which were adsorbed at specific sites, and in specific orientations, on Rh particles. The evolution of the labelled system was monitored by means of nuclear magnetic resonance spectroscopy. The results revealed the occurrence of surface diffusion, on multifaceted particles, with an activation energy of 7kcal/mol. Heterosite exchange was detected by means of the selective labelling of linearly bonded CO; except for nearest-neighbor bridge-bonded CO.

T.M.Duncan, A.M.Thayer, T.W.Root: Physical Review Letters, 1989, 63[1], 62-5