The mobility of CO which was chemisorbed onto (111) Pt was measured by using a technique which synchronized pulsed molecular-beam dosing with fast-scan infra-red interferometry. The method was based upon the observation that molecules were generally more tightly bound at defects (such as steps) where they exhibited a different internal vibrational frequency to that which was associated with the same molecule when adsorbed on a low-index terrace site. A low coverage (of about 0.06% of a monolayer) of CO was deposited, with a random spatial distribution, onto a stepped Pt (111) surface within 0.0006s. The temporal evolution of the infra-red spectrum was then recorded, with a resolution that was greater than 5ms, as the CO diffused to the steps. A simple kinetic model made it possible to extract statistical microscopic hopping rates, for CO diffusion on the (111) plane, at temperatures ranging from 95 to 195K.

J.E.Reutt-Robey, Y.J.Chabal, D.J.Doren, S.B.Christman: Journal of Vacuum Science and Technology A, 1989, 7[3], 2227-34