The oxidation of CO on Pt(100) exhibits complex non-linear behavior, such as reaction rate oscillations and spatio-temporal adsorbate patterning. The current focus of our work is to investigate the dynamics of this system when it is subjected to external forcing. Using gas microdosing to locally introduce reactants onto the catalytic surface and EMSI (Ellipsomicroscopy for Surface Imaging) to image changes in adsorbate activity, unique behavior has been observed for systems at pressures of 1x10^-4 Torr.

The local dosing of several gasses (e.g., CO, O₂, NH₃, etc.) onto the catalytic surface modifies the surface in such a way as to lead to the formation of a ring shaped pattern generated by preferential adsorption of CO. An investigation of this ring formation concluded that the appearance of the ring depends on the surface temperature at the time of microdosing as well as the time elapsed between dosing and the introduction of CO into the reactor.

External forcing was used to drive small areas of the surface residing in a monostable, CO covered state into an oscillatory state. Initial Reaction conditions were adjusted to produce a CO covered surface, lying close to the point at which the surface would become O saturated.  Oxygen was then microdosed onto the surface creating an adsorbed O island that was eventually reacted away to leave the surface covered again with only CO.  Decrease of the global CO pressure lead to the onset of oscillations, which were spatially restricted to the previously dosed regions.