Excitation waves in reaction–diffusion media with non-monotonic dispersion relations

We report results on chemical wave propagation obtained from experiments with a modified Belousov–Zhabotinsky reaction. Under pseudo-onedimensional reaction conditions, excitation pulses either form closely stacked, stable wavepackets or merge with a slow leading pulse in front-to-back collisions. Moreover, wave stacking can involve the cascading formation of metastable clusters. These phenomena are due to anomalous dispersion relations in which the derivative of the pulse speed with respect to wavelength can involve negative values. Wave stacking and merging are also observed in thin reaction layers where they affect the evolution of target patterns. Additional results on the concentration dependences of the overall dynamics and pulse speeds are presented.