THE IMPORTANCE OF DIFFUSION IN SURFACE-REACTIONS DEMONSTRATED WITH STM

We have used STM to observe directly a process which can be described as tyro-dimensional, surface-mediated Ostwald ripening, occurring duri ng the decomposition of methoxy intermediates on a Cu(110) surface. So me islands get bigger during the course of the reaction, at the expens e of smaller ones, and it is shown that this diffusion is important fo r dictating the rate of methanol decomposition. This is proposed to oc cur from the dilute phase of methoxy existing in the inter-island regi on and the methoxy maintains a pseudo steady state there, supplied by diffusion from, and between, islands of adsorbate on the surface.