MULTI-ARMED SPIRALS IN A LIGHT-CONTROLLED EXCITABLE REACTION

The dynamics and geometry of multi-armed spirals in the light-sensitive ruthenium-catalyzed Belousov-Zhabotinsky reaction were investigated experimentally. The patterns were generated by a novel technique based on laser illumination, which allows the formation, control and annihilation of spiral waves. The rotation of n-armed spirals (n <= 6) is stabilized by an unexcitable disk, created by a green laser beam. After switching off the laser, the central disk region becomes excitable again and individual cores are formed for each spiral arm. A symmetric collision structure appears periodically in the central region. Spiral arms are not attached to specific cores, but continuously passed on to the adjacent one. The geometry of multi-armed spirals is analyzed in polar coordinates and single arms are compared with a simple Archimedian shape.