Microscopic CO Diffusion on a Pt(111) Surface by Time-Resolved Infrared Spectroscopy.

A new technique, combining a pulsed supersonic molecular beam source and time-resolved surface infrared spectroscopy, has been devised to measure the microscopic diffusion of molecules at surfaces. Following a rapid dose of periodically-stepped Pt(111) crystal face to a low total coverage of CO(~0.006 ML), the time evolution of CO molecules migrating from terrace to step sites was monitored with a temporal resolution as fast as five msec. When compared with a simple kinetic model the data reveal statistical microscopic hopping rates for CO diffusion on the (111) plane over the T = 95 - 195K rang investigated.