Distinctive sites in chemical waves: The spiral core and the collision area of two annuli

Abstract

Dynamical and structural details of traveling chemical waves in an excitable solution layer of the Belousov-Zhabotinskii reaction are sensitively detected by measurements with a two-dimensional spectrophotometer and application of perspective display techniques for data analysis. Concentration gradients of the redox couple ferroin/ferriin catalyzing the reaction are determined to a resolution of about 10μm. In solutions of identical chemical composition the gradients reach peak values of 8 mM/mm in a front of a spiral and 15 mM/mm in a front of a circular wave. Variation of ferroin concentration in the center of spiral rotation is less than 6% of that outside the core region. The degree of oxidation of ferroin at which the steepest concentration gradients occur is higher inside the core than at the outward-moving fronts. The core structure and the collision area between two circular fronts are represented by three-dimensional orthographic projections.