Oscillatory clusters in the periodically illuminated, spatially extended Belousov-Zhabotinsky reaction

Cluster-cluster transitions in the periodically illuminated photosensitive Belsusov-Zhabotinsky (BZ) reaction-diffusion system exhibit the same scenario as in the autonomous BZ system with negative global feedback: two-phase clusters <-> three-phase clusters <-> irregular clusters <-> localized clusters. Transitions induced by changing the dark (TD) or light (TL) phases of the periodic external square wave illumination are dependent not only on the frequency of illumination at constant T-D/T-L, but also on the ratio T-D/T-L at constant frequency (when T-D + T-L = const).