Chemical spiral rotation is controlled by light-induced artificial cores

Abstract

Dynamic features of spiral-shaped excitation waves rotating around unexcitable disks are investigated experimentally. The spiral patterns are observed in the ruthenium-catalyzed Belousov-Zhabotinsky reaction (bromination of malonic acid), in which the excitability depends on the intensity of applied illumination. Measurements are performed with a novel technique, which uses an argon laser beam for manipulation of wave propagation and creation of unexcitable disks, serving as artificial spiral cores. Rotation period, wavelength and velocity of spirals increase monotonically when the core radius is enlarged by expanding the diameter of the laser beam (0.1–3.0 mm). Rapid change of the core size is followed by a continuous relaxation process into a new dynamic state. The transient wavelengths and velocities scanned during this process provide data for a fast calculation of the dispersion relation for the investigated medium.