We show that illumination of the chlorine dioxide−iodine−malonic acid reaction with visible light suppresses oscillations and shifts the steady state of the reaction to lower concentrations of iodide ions. In the system with starch, illumination results in a strong decrease of the steady-state concentration of the triiodide−starch complex. We suggest a simple mechanism, in which iodine atoms produced by photodissociation of molecular iodine initiate reduction of chlorine dioxide to chlorite and oxidation of iodide ions to iodine. This results in a decreased amplitude of oscillations and, at more intense illumination, the cessation of oscillations. Illumination also lowers the steady-state concentrations of iodide and the triiodide−starch complex. Results obtained from numerical simulations are in good agreement with the experimental data.

We have found a variety of oscillating patterns in the Belousov-Zhabotinsky (BZ) reaction-diffusion system with global negative feedback. Bulk oscillations and wave patterns arise at low values of the feedback strength. When the feedback exceeds a critical value, cluster patterns arise. Besides the standing, irregular, and localized clusters observed earlier, we have found new types of clusters: three-phase, localized irregular, and localized oscillatory clusters. A model of three identical Oregonators with global negative coupling yields the same bifurcation scenario as found in our experiments.

Dibromomalonic acid (Br 2 MA) oxidizes the photoexcited state of the Ru(bpy) 3 2+ complex, producing Br 2 . Br 2 MA also reduces Ru(bpy) 3 3+, yielding Br -. The first of these reactions has a rate proportional to [H + ] and plays an important part in the mechanism of photoinhibition of the Belousov-Zhabotinsky reaction. We propose a reaction mechanism that gives good agreement with the experimental data.

We show that the rate of spontaneous formation of centers of target patterns in the Belousov-Zhabotinsky reaction-diffusion system depends strongly on the concentration of the initial reagents. Computer simulations show that the dependence can be explained by the hypothesis that small heterogeneous impurities are the sources of the target patterns.

We studied the photoresponse of the chlorine dioxide-iodine-malonic acid (CDIMA) reaction. In a continuously fed stirred tank reactor, the photosensitivity increases with decreasing residence time and increasing concentration of chlorine dioxide. Under certain conditions, concentrations change in a sigmoidal fashion in response to a jump in the intensity of illumination. We propose a new mechanism for the effect of visible light on the CDIMA reaction. Simulations based on the proposed mechanism accurately describe the experimentally observed kinetics.