SYNCHRONIZATION AND SPATIOTEMPORAL SELF-ORGANIZATION IN THE NO+CO REACTION ON PT(1OO) .2. SYNCHRONIZED OSCILLATIONS ON THE HEX-SUBSTRATE

The NOS-CO reaction exhibits sustained rate. oscillations on Pt(100) under conditions where the surface is mostly hex-reconstructed. These rate oscillations have been investigated in the 10(-6) mbar range using photoemission electron microscopy as a spatially resolving method. During the rate oscillations which appear in a temperature-window ranging from 490 to 478 K, the surface reacts in a spatially homogeneous way. At the upper T-boundary of the oscillatory range, the oscillations develop via a Feigenbaum scenario leading from chaotic small amplitude oscillations at high T to regular period-1 oscillations at lower T. At the lower T-boundary of the oscillatory range, at T=478 K, target patterns appear causing the collapse of the amplitude of the rate oscillations. As the temperature is lowered further, the parallel wave trains become increasingly irregular. Spiral waves form, and finally one observes only local reaction outbursts. A model for the synchronization mechanism in the rate oscillations is proposed based on the 1x1 double left right arrow hex-phase transition, while the origin of the chaotic oscillations in this reaction system is discussed in terms of a transition from unsynchronized to synchronized oscillations.